difference in overall desirability between hot-gas and hot-water blanch-
ed samples. Similar evaluation of frozen corn-on-cob (Table 24) was
complicated by maturity difference in the samples. The significantly
lower preference for hot-gas blanched corn-on-cob due to difference in
appearance may be a deterrent to use of hot-gas blanching of this com-
modity.

The results of the taste panel ranking of canned spinach samples (Table
25) demonstrated no significant preferences among three commercial
and one hot~gas blanched samples. However, a triangle test in differ-
ences in canned spinach samples from the 1972 season did demonstrate
a significant flavor difference between hot-water blanched and hot-gas
blanched spinach.

One of the expectations for hot-gas blanching, when it was first con-
sidered, was improved retention of water soluble vitamins and min-
erals due to reduced water leaching of soluble components. The pro-
duction of a more nutritious food with hot-gas blanching would justify
part of the expense of shifting to this new method. For this reason,
and due to the need for information on nutrient retention, considerable
effort has been devoted to measuring vitamin and mineral content as a
function of the type of blanching used.

The results of nutrient retention measurements were tested for signi-
ficance in those cases where results were available for three or more
commodities. The results of nutrient analysis of thiamin (Vitamin B})),
riboflavin, (Vitamin B2), ascorbic acid (Vitamin C), Vitamin Bg, nia-
cin, phosphorus, calcium, and magnesium were subject to randomized
complete-block tests using the commodities as blocks and the blanch-
ing conditions as treatments. None of the computations produced F-
values larger than the tabulated F-values for the appropriate degrees
of freedom of the variance ratios. The over-all data available to date,
with the exception of ascorbic acid retention in canned spinach (see
Appendix N), strongly suggests that there is no significant difference in
vitamin and mineral retention when hot-gas blanching is compared to
steam or hot-water blanching. The higher level of retention of ascor-
bic acid in canned spinach from hot-gas blanching is significant and is
supported by a higher level in blanched samples compared to raw and
hot-water blanched samples.

~54-


texture, flavor and overall desirability.

The samples were served in paper cups coded with three-digit random
no. The four coded cups, randomly placed on a tray along with a

ballot and fork, were served to the judges seated in individual testing
booths. The judges were asked to score the appearance by viewing one-
cup samples in white bowls and finally score the overall desirability
and indicate which sample they preferred.

It should be noted that a different scoring system was used at the one
mo storage test than was employed on the three mo and six mo storage
tests. At the initial storage period, sample A was used as a known
reference and also included as a coded sample along with the other
samples and the judges scored the four coded samples in direct relation
to the reference (A) sample which was pegged at a score of five. How-
ever, even though the scoring system makes the absolute scores lower
on the one mo storage test, the relative differences between samples
are the main considerations.

The Oregon State University group also evaluated samples of hot-gas
blanched and commercially blanched frozen corn-on-cob.

Laboratory taste panels were run in the NCA Berkeley Laboratory on
samples of canned spinach. A set of three samples (two identical) of
commercially-blanched and hot-gas blanched spinach was presented to
a panel of sixteen persons on four occasions for determination of
difference. A ranking test of three commercially-canned samples and
one hot-gas blanched canned sample was also conducted in the NCA
Berkeley Laboratory.

By following consumer reactions to samples, adess objective, but still
highly significant, product evaluation was obtained on samples of green
beans, beets, corn-on-cob, spinach and peas which contained all or
partially hot-gas blanched material. For beets, and peas, this type of
evaluation was the only source of information on product quality as in-
fluenced by the blanching treatment received.

The results of NCA product evaluations were subjected to analysis of
variance to determine if there was a significant effect due to the blanch-

-20-


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development,

U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:

Environmental Health Effects Research
Environmental Protection Technology
Ecological Research

Environmental Monitoring
Socioeconomic Environmental Studies

APWH—

This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES series. This series describes research
performed to develop and demonstrate instrumentation, equipment
and methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.

This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.


Horwitz, W., "Official Methods of Analysis of the Association
of Official Analytical Chemists," 11th Edition, Association of
Official Analytical Chemists, Washington, D.C. (1970).

Watt, B. K., and Merrill, A. L., "Composition of Foods,"
Agriculture Handbook No. 8, Agricultural Research Service,
U. S. Department of Agriculture, Washington, D.C. (1963).

Orr, M. L., '!Pantothenic Acid, Vitamin Be and Vitamin Bio
in Foods,'' Home Economics Research Report No. 36, Agri-
cultural Research Service, U. S. Department of Agriculture,
Washington, D.C. (1969).

National Research Council, 'Recommended Daily Dietary
Allowances,'' Food and Nutrition News, 40, No. 2 (1968).

Judge, E. E., ''The Almanac of the Canning, Freezing, Pre-
serving Industries,'' Edward E. Judge & Sons, Inc., West-
minster, Maryland (1972).

Private communication with Darrell Beavers of Oregon State
University (April 1973).

Lopez, A., 'A Complete Course in Canning," 9th Edition,
pp. 105-111, Canning Trade, Baltimore, Maryland (1969).

Howard, J. W., Turicchi, E. W., White, R. H., and Fazio,
T., "Extraction and Estimation of Polycyclic Hydrocarbons
in Vegetable Oils," J. Ass. Offic, Anal. Chem., 49:1236-
1244 (December 1966).

Fazio, T., White, R. H., and Howard, H. W., ''Collabora-
tive Study of the Multicomponent Method for Polycyclic Aro-
matic Hydrocarbons in Foods,’' J. Ass. Offic. Anal. Chem.,
56:68-70 (January 1973).

-63-


APPENDIX B (continued).

SHORT DURATION HOT-GAS BLANCHING OF CUT GREEN BEANS

Run Kg/flight Product Temp,

Residence

Peroxidase

Steam

no. total feed wt/kg oC time, s c reduction, % meter, %
wt/kg

GB 1.8 107-

29 10.0 ll. 110 77 61 (20 psig)?

GB 1.8 107-

30 9.1 9.3 110 77 -- (20 psig)”

GB 1.8

31 9.0 9.3 107 17 -- (10 psig)

GB 2.1

32 9.1 9.5 110 77 0 4c

GB 2.1

33 9.5 9.6 121 77 9 4c

GB 2.1

34 9.3 9.5 110 17 19 4c

GB 1.4 106-

35 10.3 10.0 107 77 59 4c

GB 1.4 93-

36 10.0 10.1 94 77 21 4c

GB 1.4 80-

37 10.5 10.6 82 77 0 4°

GB 1.4 74-

38 8.4 8.5 77 77 0 4

-74-


opened cans containing samples of hot-gas blanched vegetables and
commercially blanched vegetables were made as a second indirect
estimation of tissue gas removal.

Vegetables are classified as low acid foods due to observed pH values
above 4.6. The pH range of vegetables permits growth and toxin pro-
duction from the mesophilic anaerobic bacterium Clostridium botuli-

num, if any spores survive in a can due to underprocessing.

The calculation of the thermal process is based on thermal death time
data for anaerobic spores and heat penetration measurement for each
product formulation. Blanching can influence the heat penetration
characteristics of canned vegetables, such as in chopped spinach, and
render an established thermal process inadequate. Blanching may
have an effect on fill weights which are another factor which must be
controlled for thermal processing adequacy. For these reasons, the
experimental plan called for examination of the effect of hot-gas blanch-
ing on critical control points in the thermal processing of canned
vegetables.

BLANCHING

The hot-gas blancher used for the in-plant studies was the experi-

mental unit described previously by Ralls and Mercer. 3

Figure 1 shows a photograph of the hot-gas blancher installed in one
of the food processing plants used in this study.

The blancher was installed with three electrical meters: one for the
large blower; one for the combustion air supply turbine; and one for
the conveyor drive, gas furnace ignitor, and electronic controls. A
gas meter was placed on the inlet side of the natural gas furnace. A
Fisher and Porter Model 10A1152-55EM steam flow meter rated at

9. 54 kg (21 1b)/ minute(min) at 100 percent of scale was installed on
the steam inlet line. A FMC Syntron Model No. BF-2 electric vibra-
tory feeder was used to control the rate of feeding of green beans and
beets onto the conveyor belt of the hot-gas blancher. Corn-on-cob
and spinach were loaded by hand by workers wearing food grade rubber

-10-


of iso-octane, the aqueous layer was discarded.

Each of the three iso-octane extracts was then washed with four
100 ml portions of warm, distilled water by pouring through the
water, followed by gentle swirling action. The aqueous layer was
drawn off and discarded after each washing.

Column Chromatography

A chromatographic column was prepared by packing with a 60 g of
Florisil which had been washed three times with methanol and acti-
vated for 16 hr in an oven at 100°C. The column should also contain
about 50 g of anhydrous sodium sulfate packed above the Florisil,
and the entire column should be prewetted with about 100 ml of iso-
octane. The iso-octane was passed in the first separatory funnel
through the column and the eluate was collected in a 500 ml beaker.
The first separatory funnel was then rinsed with the contents of the
second separatory funnel, and the iso-octane poured into the column.
The first and second separatory funnels were then rinsed consecu-
tively with the third iso-octane extract, and then poured into the
column. All of the eluate was collected in the same beaker. The
drip rate for the column should be about 20-25 drops/min.

The three separatory funnels were then washed consecutively with
50 ml of benzene, which was then poured into the column and the
eluate was collected in a separate beaker. The column was then
eluted with three 100 ml portions of benzene.

Both the iso-octane and benzene eluate were evaporated down toa
volume of 2-3 ml using warm air steam to increase the evaporation
rate. These solutions should not be allowed to evaporate to dryness
as this results in significant losses of hydrocarbons.

Thin Layer Chromatography (TLC)

Prepare five 20 x 20 cm TLC plates as follows: Homogenize 20 g

cellulose and about 100-ml water in a Waring Blender at high speed

for about three minutes. Using Kensco applicator, apply to plates

(500 u thickness) and allow to air-dry completely. Before use,

plates should be washed in a TLC tank with iso-octane and stored in
-69-


above was used, the internal temperature of the cob ranged from 32-
43°C (90-110°F); a commercial line sample taken at the end of the
water spray cooling had a cob temperature of 51°C (124°F), In the
initial tests, the bottom of the ears after the first five min of spray
cooling were distinctly warmer than the tops. In the long duration runs
the ears were rotated 180 degrees as they were held in the five min
draining station to achieve more uniform cooling.

The conditions used for hot-gas blanching of corn-on-cob were: a load-
ing rate of 22 kg/m? (4.5 lb/ft”), a feed rate of 109 kg (240 lb)/hr, a
temperature range of 99-110°C (210-230°F), a residence time of 14
min, and steam injection at a rate of 2.9 kg (6.4 1b)/min. No pH deter-
minations were made on the corn-on-cob wastewater samples.

The results of observations recorded and analyses made on product
samples collected during the long term hot-gas blanching of corn-on-

cob are tabulated in Table 5,

Table 5. LONG TERM HOT-GAS BLANCHING OF CORN-ON-COB

Date Hour of Temp, Kernel
operation4 °C peroxidase
reduction, %

9-18-72 a.m. 0 --- --
1 104 98
2 104 100
3 106 92
4 99 100
5 100 100
6 102 98
7 104 90
8 102 97
9-18-72 p.m. 9 103 100
10 102 100
ll 103 87
12 104 97
13 104 97

-27-


APPENDIX Q (continued).

CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER

WASTEWATER
4-19-73
Steam condensate = a wee aa x60x8= 52,1601
Water overflow = (eee x 60x8= 265, 1201
Dump water = 16,9801 = 16,9801
Total wastewater/8 hr = 334,0001
Weight of spinach (8.4 + 8.2 + 8.8) _
blanched = ( 3 yx 8= 67.8 kkg
Vol 8h: kkg/8 = 33 00
(Volume/8 hr)/(kkg/8 hr) 110° 4,900 1/kkg
4-12-73
BOD
Steam condensate = (2840) (48,720) _ 21k

(10°) * (65.6) ee
Water overflow = (70) (275, 160) _

(106) * (65.6 > 0.29 kg
Dump water = (3860) (16, 980) _ L.0k

(108) *( 65.6) 78
Total BOD = 3.4 kg/kkg
COD
Steam condensate = (4030) (48,720) _

(108) *( 65.6) 3.0 kg
Water overflow = (140) (275, 160)

— Teo" 0.59 kg

(108) * (5.6 )

-98-


Table 11 (Continued). LONG TERM HOT-GAS BLANCHING OF
WASHED SPINACH

Date Hour of Feed rate, Temp, Peroxidase
operation? kg/hr °C reduction, %
15 -- 104 --
16 173 110 --
4-12-73 17 -- 104 --
18 154 104 --
19 -- 99 99
20 136 113 99
21 -- 110 99
22 -- 104 99
23 132 102 99
4-13-73 24 -- 107 99
25 144 104 99
26 -- 107 99
27 -- 107 99
28 158 104 99
29 -- 107 99
30 132 104 99
31 -- 107 99
4-14-73 32 144 110 99
33 158 107 99
34 144 104 99
35 122 107 99
36 -- 110 99
37 144 107 99
38 -- 104 99
39 144 102 99
40 -- 104 99
41 156 107 99

4 Total volume wastewater samples collected from 0 to 8, 8 to 16,
16 to 24, 24 to 32, and 32 to 40 hr of operation were 1.8, 0.74,
0.42, 0.58, and 0.511, respectively.

The presence of free water on the washed spinach loaded on the feed

-34-


processing is one of the categories listed as "priority customers"
(some others are residential uses, agricultural production and mass
transit vehicles). Therefore, it is highly likely that vegetable pro-
cessors using hot-gas blanching could get adequate supplies of pro-
pane. For the longer term future, use of liquified natural gas and
new sources such as the Siberian production area and gasification of
coal should provide ample supplies up to the end of this century.

DEHYDRATION DURING HOT-GAS BLANCHING

A major reduction in operational cost would result if dehydration of
the hot-gas blanched material were accepted, as this would lower
steam cost. It is likely that partially dehydrated beets would recover
their water content after canning. Partially dehydrated corn-on-cob
may recover water during spray cooling. Neither of these possibil-
ities have been examined as yet. If it were possible to accept par-
tial dehydration of vegetables during hot-gas blanching, both opera-
tional costs and cost of wastewater treatment would be substantially
reduced.

The 1.5 percent difference in moisture content between raw and hot-
gas blanched spinach represents an 18 percent increase in solids con-
tent or approximately 2 percent actual weight loss due to the dehy-
drating effect of hot-gas blanching. This level of dehydration would
be of concern to a freezer of spinach, but for canned spinach a 2 per-
cent reduction in fill weight would provide the proper fill of container
for processing and standard of identity specifications. It is expected
that spray cooling of hot-gas blanched spinach prior to preservation
by freezing would accomplish a partial rehydration and lead to reas-
onable weight recovery.

The data shown in Appendix P confirm the observations made about
weight loss and cooling of hot-gas peas as they were conveyed approx-
imately 34 m (110 ft) from the blancher to the filler. The lower
vacuum found is due to a lower temperature of can contents at the
time of closing of the cans. There is no significant difference in
headspace. The net weight of hot-gas blanched peas was 5.6 g

[0.2 ounces (oz)] higher due to filling of more peas having a higher
average solids content. The count of peas from hot-gas blanched
samples was 2.8 percent higher than the hot-water (commercial)

-59-


samples taken at 2 hr intervals.
Beets

It was possible to develop hot-gas blanching conditions for beets which
gave raw product which peeled satisfactorily and yielded canned pro-
duct judged by cannery personnel as commercially acceptable. The
results of short-term experiments on hot~-gas blanching of beets are
tabulated in Appendix G. Due to an unexpectedly short processing
season for beets, it was possible to complete only nineteen hr of long-
duration operation. The shortened operating season also limited col-
lection of commercial blancher wastewater data by NCA personnel, in
particular, the volume and composition of blancher discharge water.

The conditions used for the nineteen hr of hot-gas blanching of beets
were: a loading rate of 29 kg/m (6 lb/ft”), a feed rate of 73-136 kg
(160-300 lb)/hr, a 106-124°C (223-255°F) operating temperature, a
25 min residence time, and a steam injection of 1.9 kg (4.2 1b)/min.
The data collected during the nineteen hr of hot-gas blanching of beets
are tabulated in Table 8.

Table 8. LONG TERM HOT-GAS BLANCHING OF BEETS

Date Hour of Feed rate, Temp, Peroxidase
operation® kg/hr oC reduction, %

10-5-72 0 0 --- ---

1 91 106 100

2 -- 122 98

3 -- 118 98

4 -- 116 100

5 -- 122 98

6 -- 124 98

7 -- 119 98

8 136 117 96
10-6-72 9 136 116 97

10 -- 120 99

ll 136 118 98

-30-


SECTION VIL
REFERENCES

Weckel, K. G., Rambo, R. S., Veloso, H., and von Elbe,

J. H., "Vegetable Canning Process Wastes,"' Research Report
38, College of Agriculture and Life Sciences, University of
Wisconsin (1968).

Weckel, K. G., unpublished data (1970).

Ralls, J. W., and Mercer, W. A., ''Low Water Volume En-
zyme Deactivation of Vegetables before Preservation," EPA
Technology Series, EPA-R2-73-193 (May 1973).

Mukai, M., Tebbens, B. D., Thomas, J. F., 'Multidimen-
tional Chromatography of Areanes Produced During Combus-
tion," Anal. Chem., 36:1126-1130 (May 1964).

Bryan, G. T., and Lower, G. M., Jr., "Diverse Origins of
Ubiquitous Environmental Carcinogenic Hazards and the Im-
portance of Safety Testing,"' J. of Milk and Food Technology,
33, 506-515 (1970).

Holdsworth, S. D., "Effluents from Fruit and Vegetable Pro-
cessing, "Process Biochem. , 3:27-31 (June 1968).

Amerine, M. A., Pangborn, R. M., and Roesslar, E. B.,
"Principles of Sensory Evaluation of Food,'' Academic Press,
New York (1965).

Dietrich, W. C., Huxsoll, C. C., Wagner, J. R., and Guadagni,
D. G., "Comparison of Microwave with Steam or Water Blanch-
ing of Corn-on-the-Cob: 2. Peroxidase Inactivation and Flavor

Retention, '' Food Technology, 24:293-296 (March 1970).
Taras, M. J., Chairman, "Standard Methods for the Investi-

gation of Water and Wastewater", 13th Edition. American
Public Health Association, Washington, D.C. (1971).

-62-


APPENDIX Q (continued).

CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER

WASTEWATER

Dump water =
Total COD =

ss

Steam condensate =

Water overflow =

Dump water =
Total SS =

4-13-73
BOD

Steam condensate =

Water overflow =

Dump water =
Total BOD =

COD

Steam condensate

Water overflow =

(4630) (16,980) _
(10) *("65.6)

(170) (48,720) _
(106) * (65.6 )~
(75) | (275,160) _
(106) * (65.6)

(160) _ (16, 980) _
(10%) * (65.6)

(3070) (52, 800)

(10°) * (64)

(80) (282,200) _

(108) * (64)

(3540) (16, 980) _
(10°) *( 64)

(3740) | (52, 800) _
(108) * (6a)

(140) (282,200) _
(108) * (64)

-99-

1.2 kg

4.8 kg/ikkg

0. 12 kg

32 kg

0, 04 kg

0.48 kg/kkg

2.5 kg

0.35 kg

0.94 kg

3.8 kg/kkg

3.1 kg

0. 62 kg


b Ice supply exhausted, no sample collected.

The characteristics of wastewater collected from the steam condensate
line of the hot-gas blancher during three eight-hr periods and one five-
hr period are tabulated in Table 17.

Table 17. WASTEWATER VOLUME AND CHARACTERISTICS FOR
HOT-GAS BLANCHING OF GREEN PEAS

Sampling Wastewater Weight BOD, COD, SS, pH
date volume, 1 blanched, mg/1 mg/1 mg/l
kkg
5-11-73 30.5 2.12 3100 4070 100 7.2
5-12-73 33.1 2.37 13800 31800 340 7.0
5-14-73 a.m. 32.6 2.12 10100 18100 440 6.0
5-14-73 p.m. 18.1 1.63 7330 14400 -- --

The commercial pea blanchers consisted of three pipes through which
the peas were pumped in hot water. The rated capacity for the three
pipe blanchers was 9.09 kkg (10 ton)/hr. The commercial pea blancher
which was monitored was a stainless steel pipe 10 centimeters (cm)

(4 in.) in diameter, approximately 34.1 m (112 ft) long, with a capacity
of approximately 3801(100 gal.). The source of make-up water for the
pipe blancher was a water manifold (3 spray lines) used to rinse and
partially cool peas after separation from the recirculated hot-water.
The flow rate of the rinse water which returned to the pipe blancher
surge tank was 9.5 1(2.5 gal.)/min based on the average of six mea-
surements. The hot-water in the pipe blancher system was discharged
about every 8 hr of operation. The results obtained on analysis of grab
samples collected every 2 hr from the surge tank are tabulated in
Appendix M. Characteristics of the commercial blancher's wastewater
samples are summarized in Table 18.

PRODUCT EVALUATION

The results of analysis of single canned samples prepared from hot-gas
or commercially-blanched material for headspace gas composition are

-40-


APPENDIX F (continued)

WASTEWATER VOLUME AND CHARACTERISTICS FOR STEAM
CONSENSATE GRAB SAMPLES FROM COMMERCIAL BLANCHER
FOR FROZEN CORN-ON-COB

-82-

Sampling Feed rate Weight Volume, BOD, cob, ss,
date ears/min blanched, 1 mg/1 mg/1 mg/1
kkg
(4-6 hr) 79 2.87 129 13600 20700 980
(6-8 hr) 54 1.96 134 16600 24800 980
9-19-72 a.m.
(0-2 hr) 61 2.22 166 10500 15700 490
(2-4 hr) 48 1.74 254 10700 14000 590
(4-6 hr) 91 3.31 247 15400 23100 1500
(6-8 hr) 63 2.29 252 16200 24200 1700
9-19-72 p.m.
(0-2 hr) 85 3. 08 312 12800 20900 1450
(2-4 hr) 77 2.80 306 14800 23400 1780
(4-6 hr) 64 2.32 213 12500 19600 1980
(6-8 hr) 78 2.83 227 15500 24600 2120
9-20-72 a.m.
(0-2 hr) 93 3.38 242 14500 23100 770
(2-4 hr) 141 5.12 321 13400 21400 830
(4-6 hr) 79 4.14 312 13100 20800 890
(6-8 hr) 79 2.87 275 13800 21700 940


SECTION III
INTRODUCTION

The food processing industry is now evaluating the economic conse-
quences of radical changes in processing equipment as one option
available to assist the industry in meeting the national goal of zero
discharge of pollutants by 1985. It is likely that new technology for
raw product preparation, which substantially reduces waste genera-
tion, will cost less when old equipment is replaced than the cost of
installation or expansion of treatment facilities. New equipment which
produces little or no liquid waste would be advantageous if total re-
cycle use of water in food processing is shown to be possible.

Vegetables which are preserved for long-term storage by freezing,
dehydration, or canning, receive a treatment (known as blanching)
with hot-water or steam. The purpose of blanching is to deactivate
enzymes and to remove tissue gases. In addition, blanching fre-
quently accomplishes or facilitates removal of juice, soil, insects and
other debris from the vegetable pieces.

It has long been known that the blanching of vegetables is a source of
strong liquid wastes with a potential for pollution of receiving water.
For example, the blanching and peeling of beets, carrots, and potatoes
account for 85, 65, and 89 percent, respectively, of the five-day bio-
chemical oxygen demand (BOD) generated in the processing of these
commodities, Weckel et. al. 1 It has been estimated, Weckel, 2 that
the national (United States) amortized annual (1969) treatment facility
cost for liquid wastes from selected vegetable blanching is $2,400,000
and the annual operating and maintenance cost is $3,000, 000.

The blanching of vegetables, therefore, is a food processing unit
operation having a high potential for substantial reduction in liquid
waste generation. The volume of liquid waste produced from hot-
water blanching of vegetables is 10-20 times that produced by steam
blanching. Therefore, the greatest opportunity for significant re-
duction of waste water volume during vegetable processing is the re-
placement of hot-water blanching by a system generating little or no


TABLE OF CONTENTS

1

Abstract

List of Tables

Acknowledgments
Sections

I. Conclusions

Ii. Recommendations
Ill. Introduction

IV. Experimental Plan

VIL

VIL.

Vill.

Ix.

General Considerations
Blanching

Wastewater Measurements
Product Evaluation
Economics

Experimental Results
Blanching and Wastewater Measurements
Product Evaluation
Energy Requirements

Discussion
Blanching, Wastewater, and Product Evaluation
Comparison of Costs of Blanching Systems
Dehydration During Hot-Gas Blanching
Overall Considerations

References

Glossary

Appendices

-iii-

iv

vii

10
13

16
al

23
23
40
47
49
49
55

59
60

62

64

66


Table 14 (continued). STEAM CONDENSATE AND MAKE-UP WATER
OVERFLOW RATES FOR COMMERCIAL
SPINACH BLANCHER

Sampling dates Weight Steam Water
and times blanched, condensate overflow
kkg/hr discharge rate, discharge rate,
1/min 1/min
4-16-73 lpm 8.8 102 527
3 pm 8.4 110 585
4-18-73 12pm 8.2 117 545
2 pm 7.8 76 604
4 pm 8.6 102 545
4-19-73 10am 8.4 102 481
12 pm 8.2 110 572
2 pm 8.8 114 604

The hot water in the blancher tank was drained three times each day;

it had a volume of 16980 1 (4480 gal.). The characteristics of the
blanch water are tabulated in Table 15 along with the results from ana-
lysis of samples of steam condensate and water overflow discharge
lines. Additional data collected during the 1972 season are tabulated in
Appendix K.

Table 15. CHARACTERISTICS OF COMMERCIAL SPINACH BLANCHER
DUMP WATER, STEAM CONDENSATE, AND MAKE-UP
WATER OVERFLOW

Sampling Sample BOD, coD, ss, pH
date type mg/l mg/1 mg/1
4-12-73 Dw* 3860 4630 160 6.2
sc-c> 2840 4030 170 6.0
wo-cc 70 140 75 7.5
4-13-73 DW 3540 5050 190 5.8
SC-C 3070 3740 230 5.9

-37-


APPENDIX A

PROCEDURE FOR DETERMINATION OF POLYNUCLEAR HYDRO-
CARBONS IN CANNED GREEN BEANS

Introduction

The following procedure for extraction and determination of polycyclic
aromatic hydrocarbons was adapted from the publications of J. W.
Howard et.al. (17, 18) of the Division of Food Chemistry, Federal
Food and Drug Administration, Washington, D.C. Using an alco-
holic potassium hydroxide solution, the vegetable sample was digest-
ed by refluxing for 2.5 hr. The hydrocarbons were extracted into
iso-octane, loaded onto a Florisil column, and eluted with benzene.
The eluate was concentrated and chromatographed using reverse
phase partition thin-layer chromatography. The hydrocarbons were
then extracted from the plate absorbent, and the fluorescence mea-
sured quantitatively.

Extraction

To a one 1 round-botomed flask were added 200 g of homogenized
sample, 400 ml of 95 percent ethanol, 50 g of KOH pellets, and
boiling chips. The flask was fitted with a condenser in the reflux
position, and the digestion was allowed to continue for 2.5 hr, re-
fluxing at a rapid rate.

At the end of the digestion, the contents of the flask were filtered,
while still hot, through glass wool into a one | separatory funnel.
The flask was then rinsed with two 50 ml portions of warm, dis-
tilled water (about 120°F), followed by two 50 ml portions of 95 per-
cent ethanol, and finally with 50 ml of iso-octane. Each washing
was poured through the glass wool into the separatory funnel.

The funnel was shaken for three min, the layers allowed to separate,
and the lower aqueous layer drawn off into a second sepatatory
funnel. This aqueous layer was then extracted a second time with
100 ml of iso-octane, and the aqueous layer drawn off as before into
a third separatory funnel. Following a third extraction with 100 ml

-68-


APPENDIX C (continued)

PREPARATION CONDITIONS AND QUALITY EVALUATION OF
CANNED SAMPLES OF HOT-GAS BLANCHED GREEN BEANS

Run Can Brine Exhaust Headspace Quality
no. size temp, box temp, vacuum, evaluation
°C °C cm, Hg
GB 10 88 74 12.7 Overblanched,
41 soft texture
GB 10 88 74 17.8 Good flavor,
42 no sloughing
GB 10 85 71 12.7 Good flavor,
43 no sloughing
GB 10 88 74 15.3 Good flavor,
44 no sloughing

4 Can 8.09 cm in diameter and 11.02 cm high (3 3/16 x 4 3/8 in. ).
b Can 15.71 cm in diameter and 17-76 cm high (6 3/16 x 7 in.).

APPENDIX D

WASTEWATER VOLUME AND CHARACTERISTICS FOR MAKE-UP
WATER OVERFLOW GRAB SAMPLES FROM COMMERCIAL
BLANCHER FOR CUT GREEN BEANS

Sampling Volume, BOD, COD, 88, pH
date 1 mg/1 mg/l mg/l
(operating
time)
8-15-72
(0-2 hr) 458 6790 11600 1490 5.9

-77-


EPA-660/2-74-091
DECEMBER 1974

Environmental Protection Technology Series

Continuous In-Plant Hot- Gas
Blanching of Vegetables

we ~*~

Sw

“Al prove

nolan,
“Oy agen’

s

Nationa Environmental’ Research Center.

Office of Research ‘and Development

U.S, ‘Environmental-Protection Agency
Corals, Oregon’ 97330


APPENDIX R (continued).

COST ESTIMATE FOR COMMERCIAL PIPE BLANCHER AND HOT-
GAS BLANCHER FOR GREEN PEAS

Cost Estimate for Commercial Hot-Gas Blancher
[5 kkg (5.5 tons)/hr]

Annual fixed cost

Amortization = FC x crf (7%, 5 yr = 0.24389) = $ 24389. 00
Space rent = 12000. 00
Taxes [$5. 00/$100 assessed value (25% of FC)] = 1250. 00
Insurance (0.2% of assessed value) = 50. 90
Maintenance (1.5% of FC/yr) = 1500. 00
Total = $ 39189. 00/yr
Hourly fixed cost (1800 hr/yr) = 21. 77/hr

Hourly operating costs

Electrical power =$ 4,45
Steam = 1,87
Water = 0. 00
Gas = 0.22
Waste disposal = 0.01
Labor (half-time worked at $5. 20/hr) = 2.60
Total =$ 9.15/hr

1
an

Hourly fixed cost 21.77
Hourly operating cost = 9.15
Total hourly cost 30,92
Cost per kkg blanched $ 6. 18/kkg

-103-


ABSTRACT

An experimental hot-gas blancher was operated in two food process-
ing plants using spinach, green beans, corn-on-cob, beets, and
green peas. A side stream of commercially prepared vegetables was
hot-gas blanched and returned to the production line. Wastewater
samples were collected from the commercial blanchers and the hot-
gas blancher; these were measured for volume and analyzed for pH,
COD, BOD, and SS. Electrical, gas, and steam flow meters were
used to obtain data for cost estimates of commercial scale hot-gas
blanching. Comparisons were made of potential reductions in volume
of wastewater, weight of BOD, and weight of SS generated when con-
ventional steam or hot-water blanching was replaced by hot-gas
blanching; in the case of spinach these reductions were 99.9, 99.8,
and 99.5%, respectively, Preserved (canned or frozen) samples of
blanched vegetables were analyzed for vitamin and mineral content.
The retention of nutrients was the same for hot-gas blanching and
commercial blanching except for retention of ascorbic acid in spinach
and green peas where hot-gas blanched samples had higher retentions.
Evaluation of flavor, texture and appearance of preserved samples
demonstrated similar quality products from hot-gas blanching and
commercial blanching. The overall quality of hot-gas blanched vege-
tables was well within the range of commercial acceptability. Esti-
mated capital costs for a commercial scale hot-gas blancher for green
beans are twice that of a hot-water blancher. The estimated operat-
ing costs for hot-gas blanching of green beans are 25% less than those
for hot-water blanching of green beans.

This report was submitted in fulfillment of Project Number S-800250
under the sponsorship of the Office of Research and Development,
U.S. Environmental Protection Agency and the Research Foundation

of the National Canners Association. Work was completed as of
September 1973.

-ii-


APPENDIX S

CALCULATION OF COST OF HOT-GAS BLANCHING OF PEAS

Electrical power:

140+ 110+4 = 254 = 8.46 kw/hr
30 30

Scale-up factor = 15
8.46 x 15 = 127 kw/5 kkg
127 x $0. 035/kw = 1.27 x 10% x 3.5 x 1072 = 4.45 x 10° = $4,45/5 kkg/hr
Steam:
1.7 kkg/30 hr = 0, 0567 kkg/hr
Scale-up factor = 15
15 x 0. 0567 = 0.85 kkg/hr
$2.20 x .85 = $1.87/hr
Gas:
16.4m7/30hr = 0,546 m3/hr

Scale-up factor = 15
15 x 0.546 = 8.2 m?/hr

(8.2) _

(28.3) * $0.76 = $0, 22/hr

Waste disposal: (80 percent removal)
0.124 kg/kkg BOD+SS =  .620 kg/5 kkg
0.620 x $0.023/kg = $0. 0143/5 kkg

-104-


The wastewater volume and characteristics for hot-gas blanching of
cut green beans are tabulated in Table 3.

Table 3. WASTEWATER VOLUME AND CHARACTERISTICS FOR
HOT-GAS BLANCHING OF GREEN BEANS

Sampling Wastewater Weight BOD, coD, ss, pH

date volume, 1 blanched, mg/1 mg/l mg/1
kkg
8-15-72 0.4734 5.33 1170 2670 140 7.2
8-16-72 0.113 3. go 6380 15500 450 6.8
8-17-72 --¢ 5.95 -- eo oe --
8-18-72 0. 620 6.49 3530 7260 180 --d
8-19-72 0.246 6.85 6840 17400 550 6.7

@ Eight hr collection periods.

For period of 11 to 16 hr of operation.
© Sample spilled

Data not recorded.

The commercial green bean blancher was a cylindrical tank, partially
filled with 1133 1 (300 gal.) of hot water. The blancher water was
drained about every eight hr. The wastewater volume and character-
istics of the make-up water overflow from the commercial cut green
bean hot-water blancher are tabulated in Table 4. The composite
samples were prepared from equal volumes of each of four grab samples
taken at 2 hr intervals.

The volume of make-up water overflow was highly variable as shown by
the data in Table 4. The variability was due to the use of different set-
tings of control valves for the make-up line and non-uniform practice in
turning off valves when the complete canning line was not operating due
to mechanical failures or rest periods. See Appendix D for additional
data.

-25-


APPENDIX H

WASTEWATER VOLUME AND CHARACTERISTICS FOR MAKE-UP
OVERFLOW GRAB SAMPLES FROM COMMERCIAL BLANCHER FOR
BEETS

Sampling Weight Volume, BOD, CoD, ss,
date blanched, 1 mg/1 mg/l mg/1
(operating kkg
time)
10-5-72
(0-2 hr) 5.55 489 13800 20000 520
(2-4 hr) 5.36 511 13500 19400 220
(4-6 hr) 5.42 515 13200 19000 170
(6-8 hr) 5.45 484 14500 21800 270
10-6-72
(0-2 hr) 5.47 257 12100 16900 290
(2-4 hr) 5.58 227 11700 16300 240
APPENDIX I

SHORT DURATION HOT-GAS BLANCHING OF SPINACH (1972)

Run Feed Product Temp, Residence Perosidase
no. wt, kg wt, kg °C time, sec inactivation, %
TLSP-1 4.5 2.7 116-121 154 99
TLSP-2 4.1 2.3 116-121 183 99
TLSP-3 3.9 2.0 113-118 210 99
TLSP-4 4.0 2.2 116-121 330 99
TLSP-5 4.8 3.0 118-121 144 99
TLSP-6 4.8 3.0 113-121 83 94
TLSP-7 3.9 2.3 116-121 108 99
TLSP-8 90.9 81.8 104-121 108 99

-84-


APPENDIX E

SHORT DURATION HOT-GAS BLANCHING OF CORN-ON-COB

Run Kg/flight Product Temp, Residence Peroxidase Steam
no. total feed wt,kg °c time,min reduction, % meter, %
wt/kg

coc-1l 2.1

8.9 8.8 129 8 -- 3°
COC-2 2.1

9.5 9.3 138 8 53 3
COC -3 2.1

9.2 9.0 154 10 -- 5
COC-4 2.1

9.0 8.5 121 19 -- 10
COC-5 2.1

9.4 9.0 113 19 100 10
CcOc-6 2.1

9.8 8.9 99 37 96 4
COC-7 2.1

9.6 9.4 104 13 90 10
CcOC-8 2.1

9.2 9.3 97 13 96 10
cOoc-9 2.1

9.0 8.9 99 16.5 92 8
cOc-10 2.1

9.2 9.1 107 16.5 100 10

-79-


SECTION IV
EXPERIMENTAL PLAN
GENERAL CONSIDERATIONS

The study of hot-gas blanching in commercial canning and/or freezing
plants was designed to collect sufficient data to provide a basis for
management decisions on the use of this new blanching system. To
evaluate all possible options, a manager would need to know capital
cost, operating cost, ease of sanitation and maintenance, product
quality, effect on containers, and cost of waste management for each
blanching system under consideration. Therefore, the hot-gas blanch-
er was operated and sampled in a way which would provide the neces -
sary data for comparison to the steam or hot-water blanchers which
are now in use.

The in-plant location of the hot-gas blancher provided access toa
readily available supply of vegetables prepared for blanching under
commercial conditions. The option of returning hot-gas blanched
vegetables to the commercial production line was available and, if used,
demonstrated the immediate commercial utility of hot-gas blanching.
The opportunity for extended operation of the hot-gas blancher made it
possible to use material from all stages of the production season and
provided assurance that raw product variation would not limit the utili-
zation of hot-gas blanching to any specific time span of the operating
season. A target of forty hr of operation for each of the five vege-
tables scheduled for study was established to provide the long term
testing period.

The in-plant testing program provided the opportunity for sampling of
commercial blanchers receiving lots of vegetables identical to those
being hot-gas blanced. Volumetric measurement and analysis of
samples of wastewater from commercial blanchers provided a basis
for direct comparison of the waste generating characteristics of hot-
gas, steam, and hot-water blanching. While it is well known that wide
variations exist in the waste generating characteristics of blanchers in
different plants processing the same commodity, Holdsworth®, such
comparisons should establish the approximate extent of waste reduction

-7-


SECTION VI

DISCUSSION
BLANCHING, WASTEWATER, AND PRODUCT EVALUATION

Any modification in food processing equipment must be rigorously
evaluated in terms of reliability, safety, ease of sanitation, mainten-
ance, and cost per unit of material processed. In recent years, the
rate of generation of gaseous, liquid, and solid by-products as poten-
tial contributors to air, water, and soil pollution has become an im-
portant food processing equipment design criteria. The final product
which results from use of modified processing equipment must be at
least equivalent in wholesomeness, texture, flavor, appearance, and
nutritive value to the product prepared with current equipment. During
the course of this investigation of in-plant, hot-gas blanching of vege-
tables, all of the above outlined criteria were evaluated albeit at vari-
ous degrees of completeness.

The prime motivation of this study was the attempt to demonstrate
commercial feasibility of a new blanching system which would sub-
stantially reduce the volume of liquid wastes now produced during
steam or hot-water blanching of vegetables. Therefore, much atten-
tion was devoted to measurement of wastewater generation from both
the hot-gas blancher and the commercial blanchers. As the critical
evaluation centered on reduction of waste treatment costs possible with
the new blanching system, wastewater measurements were made for
volume, BOD, COD, SS, and pH. Table 27 gives a summary of the
comparisons of wastewater volume, BOD, COD, and SS for hot-gas and
commercial blanching of five vegetables. The values tabulated in Table
27 are expressed in percentages in Table 28.

It must be emphasized that the percentage reductions shown, apply to
only one location and it is well known that water usage and waste gen-
etation vary over a wide range for different plants processing the same
commodity, (Holdsworth®), In any consideration of the commercial
application of hot-gas blanching, it would be necessary to use data on
wastewater generation from each individual operation to calculate ex-
pected percentage reductions.

It was not possible to evaluate completely the factors of equipment
reliability, maintenance, ease of sanitation, and safety because the

-49-


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a desiccator.

Two TLC tanks should be prepared and allowed to equilibrate for
about one hr before use, one with iso-octane (mobile phase solvent),
and another with 20 percent dimethyl formamide (DMF) in ethyl
ether (immobile phase solvent).

The two concentrated extracts were now applied to the cellulose
plate in a streak (about 0.5 cm x 10 cm) about 1.5 cm from the
bottom of the plate. Both extracts were applied to the same streak,
and the beakers rinsed with three small portions of benzene, which
were also applied to the same streak. A standard solution of pyrene
and fluoranthene in iso-octane was also applied in a streak adjacent
to the extract.

The plate was inverted and placed in immobile solvent tank, allow-
ing solvent to wet to within 0.5 cm of applied streaks. The plate

was removed from tank and excess solvent was allowed to drain from
plate (about 15-20 sec). Then plate was re-inverted and placed in
iso-octane tank and allowed to develop in dark until solvent reached
top of plate (about 1 hr).

When development was complete, plate was removed from tank and
viewed under short-wave UV light, outlining pyrene -fluoranthene
band. It was scraped and collected in a small Erlenmyer flask.
Hydrocarbons were extracted with three 5-10 ml portions of hot
methanol, and filtered through Whatman No. 1 filter paper into a
small beaker. Methanol was evaporated down to less than 10 ml
and transferred to a 10 ml volumetric flask. Beaker was rinsed
with methanol and flask made up to 10 ml.

Quantitative Analysis

Fluorescence of the extract was measured in a fluorometer at the
10-times sensitivity setting using a 7-60 primary and 2A-12 secon-
dary filter. This filter combination was experimentally found to
yield the most satisfactory results with pyrene and fluoranthese. A
methanol blank should always be run. The standard solution used
contained 1 ug/ml each of fluoranthene and anthracene in iso-octane,
giving a 2 ug hydrocarbon/ml solution. An equal ratio of pyrene to

-70-


Table 8. (Continued), LONG TERM HOT-GAS BLANCHING OF BEETS

Date Hour of Feed rate, Temp, Peroxidase
operation® kg/hr °C reduction, %

12 -- 117 98
10-10-72 13 -- 122 98

14 73 119 98

15 -- 119 97

16 -- 123 98
10-11-72 17 91 120 98

18 77 121 96

19 -- 116 100

2 Total volume wastewater samples collected at 0 to 4, 4 to 8, 8 to 12,
12 to 16, and 16 to 19 hr of operation were 37.9, 18.9, 25.5, 35.2,
and 35.01, respectively.

The wastewater volume and characteristics for hot-gas blanching of
beets are tabulated in Table 9. No measurements of pH were made on
wastewater samples from hot-gas blanching of beets. Additional data
are tabulated in Appendix H.

Table 9. WASTEWATER VOLUME AND CHARACTERISTICS FOR
HOT-GAS BLANCHING OF BEETS

Sampling Wastewater Weight BOD, coD, ss,
date volume, 1 blanched, mg/1 mg/1 mg/l
kkg
10-5-72 56.84 0.773 5360 8050 300
10-6-72 25.5 0. 544 -- -- --
10-10-72 35.2> 0.292 7140 10900 150
10-11-72 35, 0¢ 0.271 q a a
a ight hr of operation.
b Four hr of operation.
4 Three hr of operation

Sample lost.
-31-


Table 20 (Continued). NUTRIENT CONTENT OF RAW, HOT-GAS
BLANCHED, AND COMMERCIALLY BLANCHED
VEGETABLES (mg/100 g wet weight)

Commodity Nutrient Raw Hot-gas Commercially
blanched blanched
Niacin 0.46 0. 36 0.51
Calcium 32 31 38
Magnesium 19 17 23
Phosphorus 20 18 21
Corn Vitamin B, 0.12 0.18 0.16
Vitamin B2 0. 04 0. 04 0.04
Vitamin Bg 0.20 0.20 0.20
Niacin 1.9 1.9 1.9
Phosphorus 92 90 86
Beets Vitamin B 2? -- 0. 03 0.05
Vitamin C 4 -- 2.7 3.0
Niacin® -- 0. 06 0.09
Phosphorus -- 110 97
Spinach Vitamin A 2.41 4.41 4.14
Vitamin Bg 0.15 0. 13 0.10
Vitamin C 0 12.2 7.0
Calcium 47 66 66
Magnesium 55 66 45
Phosphorus 33 33 40
Iron 2.6 3.1 2.5
Peas Vitamin By 0.31 0.39 0.40
Vitamin Bz 0.12 0.13 0.09
Vitamin B6 0.19 0. 23 0.16
Vitamin C 15.4 22.5 11.4
Niacin 2.13 2.27 1.94
Calcium 25 23 20
Magnesium 34 36 29
Phosphorus 89 93 79
Iron 2.0 3.0 1.9

a Analysis conducted on canned samples.

-43-


Table 26. ENERGY CONSUMPTION DURING HOT-GAS BLANCHING
OF VEGETABLES

Cumulative
Cumulative electrical energy used, kwh
operational blower turbine conveyor Cumulative Cumulative

hr controls steam use, gas use,
kkg m?>
Green Beans
8.6 33 6 3 0.15 4.25
16.6 59 12 5 0.29 7.65
24.4 90 17 7 0.42 11.3
32.2 120 22 10 0.56 14.7
41.1 150 28 13 0.71 17.8
Corn
8.5 12 4 1 1.5 7.09
16.0 29 8 2 2.7 8.21
23.3 40 13 3 4.0 11.3
32.1 57 17 4 5.5 18.5
37.0 64 21 4 6.4 20.4
Beets
7.9 14 6 1 0.9 11.3
14.4 25 ll 2 1.6 13.6
19.0 23 18 5 2.2 15.9
Spinach
7.0 88 19 4 0.38 3. 96
15.0 180 33 7 0.82 A. 82
22.0 280 43 15 1.2 6.23
Peas
8.0 40 29 2 0.46 4,53
16,0 81 58 3 0.73 8.78
24.0 120 87 4 1.2 12.8
30.0 140 110 4 1.7 16.4

-48-


The results of analyses for polynuclear hydrocarbon content of canned
green bean samples are tabulated in Table 21.

Table 21, LEVELS OF POLYNUCLEAR HYDROCARBONS IN CANNED
GREEN BEAN SAMPLES

Sample Fortification Polynuclear hydrocarbon
level, ppb content, ppb

°
3

87
1

Hot-water blanched
Hot-gas
Hot-water
Hot-water
Hot-gas
Hot-gas
Hot-water
Hot-gas
Hot-water
Hot-water
Hot-gas

OCNUAAWOAANA

re
coo0eooeccoC oc Oo

NADNWRUDON

The sequence of results are tabulated in the order in which each analy-
sis was made. The same set of glassware was used to saponify and ex-
tract each sample. See Appendix A. The downward trend in results
indicated contamination of the glassware by the high-level fortified [100
parts per billion (ppb)] sample. As subsequent analyses were run,
material was slowly released from adsorption on glass surfaces to give
values higher than actually present. The glassware was rinsed with
hot nitric acid prior to the last analysis and the result was below the
sensitivity level of 2 ppb.

A maturity determination was made with canned pea samples. A large
part of the score (50 of 100 maximum points) in the quality grading of

canned peas is the maturity and tenderness factor. The maturity fac-

tor is derived from a flotation test of peas in sodium chloride brines of
11, 13, and 15 percent concentration. Eleven cans from the commer-
cial line packed on 5-12-73, one can packed from all hot-gas blanched
peas on 5-12-73, and 12 cans from all hot-gas blanched peas packed on

~44-


APPENDIX B (continued).

SHORT DURATION HOT-GAS BLANCHING OF CUT GREEN BEANS

Run Kg/flight Product Temp, Residence Peroxidase Steam

no. total feed wt/kg °C time,sec  reduction,% meter, %
wt/kg

GB 1.8

19 10.5 10.5 107 73 98 (40 psig)”

GB 1.8

20 10.3 10.4 110 77 95 (40 psig)?

GB 1.8

21 9.7 10.2 110 77 -- (40 psig)?

GB 1.8 104-

22 10.5 10.4 110 77 80 (40 psig)>

GB 1.8 116-

23 9.9 10.7 121 77 87 (40 psig)»

GB 1.8 116-

24 8.3 8.4 127 77 86 (40 psig)b

GB 2.8 104-

25 9.7 10.2 107 77 87 (30 psig)b

GB 2.8 104-

26 10.2 10.1 107 77 -- (30 psig)b

GB 2.8 104-

27 9.9 10.0 107 77 63 (20 psig)

GB 2.8

28 9.1 9.6 107 77 0 (10 psig)

-73-


APPENDIX G

SHORT DURATION HOT-GAS BLANCHING OF BEETS

Run Feed Product Temp, Residence Steam Peroxidase
no. wt,kg wt, kg °C time, min flow, reduction, %
kg/min

B-1l 9.1 8.4 121-132 5.5 70° Underblanched

B-2 9.1 7.5 124-138 6.5 40> Underblanched

B-3 9.1 8.9 124-132 2.4 40> Under blanched

B-4 9.1 8.1 124-132 6.5 100> Good peel,
loosening

B-5 9. 12 8.4 121-128 18.5 80> Underblanched,
soft peel

B-6 6.4 5.0 118-123 14 1.0 Good peel,
loosening

B-7 10.0 8.0 113-122 14 1.8 99.9

B-8 9.2 7.8 110-117 14 4.5 coer

B-9 9.4 7.5 102-112 14 4.4 ----

B-10 22.3 19.3 79-87 21 1.0 100

B-ll 21.4 21.1 133-138 1 1.0 0

B-12 20.0 17.9 83-88 30 0.5 95

B-13 22.5 21.4 81-82 20 0.5 ciated

B-14 18.4 17.5 80-82 20 0.5 95

B-15 9.6 8.9 110-115 8 0.4 73

B-16 11.0 10.0 111-118 14 0.4 99

B-17 8. 18.0 113-115 14 1.0 Underblanched

B-18 9.7 8.6 118-121 16 2.2 91

B-19 9.2 8.2 121 20 2.2 96

B-20 10.1 8.9 114-122 23 2.2 100

B-21 10.7 9.5 113-121 26 1.9 99

B-22 9.2 8.2 118-124 25 1.9 99

B-23° 20.0 18.6 113-121 26 19 ieee

a Large beets used.

b Steam pressure gauge reading made during temporary closing of in-
let steam valve in 1b/in.%.

c Beets put through peeling line during plant lunch break, canned for
evaluation,

-83-


Table 15 (continued). CHARACTERISTICS OF COMMERCIAL SPINACH
BLANCHER DUMP WATER, STEAM CONDEN-
SATE, AND MAKE-UP WATER OVERFLOW

Sampling Sample BOD, COD, ss, pH
date type mg/l mg/1 mg/1 _

4-13-74 wo-c 80 140 12 7.7

4-19-73 DW 3390 4050 150 6.8

SsC-C 2740 3160 130 6.7

wo-C 70 120 20 7.5

a DW Single sample of dump water

> sc-c Composite of equal volumes of steam condensate grab sam-
ple collected at 2,4,6 and 8 hr.

© WO-C Composite of equal volumes of make-up water overflow grab
samples collected at 2,4,6 and 8 hr.

Green Peas

The results of short-duration hot-gas blanching runs for green peas are
tabulated in Appendix L. The conditions used for the long-duration hot-
gas blanching of peas were: a loading rate of 14.6 kg/m® (3 lb/ft”), a
feed rate of 182-490 kg (400-1080 1b)/hr. 99-132°C (210-270°F) oper-
ating temperature with an ave. steam flow rate of . 94 kg (2. 08 1b)/min.
Due to the differences in size and maturity of peas available for hot-
gas blanching, the residence time was varied between 108 and 240 sec.
The variation in residence times accounts for the wide variation in

feed rates. The results of 30 hr of hot-gas blanching of peas are tab-
ulated in Table 16.

Table 16. LONG TERM HOT-GAS BLANCHING OF GREEN PEAS

Date Hour of Feed rate,

, Temp, Peroxidase
operation@ kg/hr °C reduction, %
5-11-73 0 _ _
1 288 121 99

-38-


EPA-660/2-74-091
December 1974

CONTINUOUS IN-PLANT HOT-GAS

BLANCHING OF VEGETABLES

By

Dr. Jack W. Ralls
Mr. Walter A. Mercer

Grant No. S-800250
Program Element 1BB037
21 BAB/029

Project Officer

Mr. Harold W. Thompson
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330

NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH & DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330

For sale by the Superintendent of Documents, US, Government Printing Office
Washington, DC 20402 - Stock No 5501-00983


APPENDIX Q (continued).

CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER

WASTEWATER

Dump water = (4050) x (16, 980) |
(10°) * (67.8) >

Total COD =

ss

Steam condensate = (139) (52,160) _
(10°) *( 67.8)

Water overflow = (20) (265,120) _
(10°) *( 67.8 ) >

Dump water = (150) (16,980) _
(10°) *( 67.8)

Total SS =

1.0 kg

3.9 kg/kkg

0.10 kg
0.08 kg

0. 04 kg
0.22 kg/kkg

Use of above values in partial calculation of the cost of commercial

blanching of spinach [5 kkg (5.5 tons)/hr].

Water cost = 2900 + 3100 + 5200 + 5500 + 4900 «5

5
4320 1x $0. 10/3785 1

BOD disposal cost = 3.4+ 3.8+ 3.9 x
3
18.5 kg x $0. 023/kg

5

SS disposal cost = 0.48 + 0.29 + 0.22
3
= 1. 65/kg x $0. 023/kg

x5

Total waste disposal cost = $0. 47/5kkg spinach blanched.

-101-

4320 1/5kkg
$0.11

18.5 kg/5kkg
$0.43

1.65 kg/5kkg
$0. 038


hot-gas blanching are: (1) shortage of potable water, (2) good supply
of natural gas or propane, (3) high costs of liquid waste disposal and,
(4) a commodity which regains dehydration losses readily.

For the long term future, as food processing operations move toward
total in-plant recycle of reconditioned water, the use of hot-gas
blanching will increase due to its potential for adequate blanching
with minimum generation of liquid waste.

-61-


nificant at the p=0.01 level) matchings of two identical samples.

In a second type of evaluation, a ranking test of flavor preference using
three commercially-canned samples and hot-gas blanched spinach
(canned under commercial conditions) gave the results tabulated in
Table 25,

Table 25. TASTE PANEL RANKING OF THREE COMMERCIAL AND
ONE HOT-GAS BLANCHED SAMPLE OF CANNED SPINACH

Sample Brine salt content, % Taste panel ranking®
Commercial A 1.16 3,04
Commercial B 0.85 2. 62
Commercial C 0.94 2.04
Hot-gas 0.96 2,38

a 1 = Best flavor; 4 = Worst flavor; 56 judgments.

In addition to the laboratory organoleptic evaluations, very substantial
quantities of commercial production of green beans, corn, beets,
spinach, and green peas containing material from hot~gas blanching
were sold. No adverse consumer reaction was recorded,up to the
time of this report about any of these production lots, which could be
attributed to the blanching used.

ENERGY REQUIREMENTS
Electrical, gas and steam flow meters on the hot-gas blancher were
used to develop information on power requirements. The energy con-

sumption values obtained during hot-gas blanching of green beans, corn-
on-cob, beets, spinach and peas are tabulated in Table 26.

-47-


APPENDIX P (continued)

VACUUM, HEADSPACE, NET WEIGHT, COUNT, AND MATURITY
OF CANNED GREEN PEAS

Vacuum, Headspace, Net wt, No. of 50 sinking in NaCl brines
in. of Hg in, /32 oz Count 11% 13% 15%

Hot-gas blanched

6 ll 17.1 718 17 12 0
6 10 17.1 702 17 2 0
5 13 16.9 687 29 10 3
8 ll 17.0 678 26 8 1
Ave.
6 12 17.0 690 20 7 1
APPENDIX Q
CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER
WASTEWATER
3-28-72
Steam condensate = 6800 l/hr x 8 = 54,4001
Water overflow = 13600 1/hr x 8 = 109, 0001
Dump water = 16,9801
Total wastewater/8 hr = 180,380 1
Weight of spinach (174 ) _
blanched = (22.5) *8= 62 Kg
(Volume/8 hr)/(kkg/8 hr) = 180, 380
62 = 2900 1/kkg

-96-


ing condition used in the preparation of samples on which the measure-
ment was made. The analysis of variance was made using a random-
ized complete block design, Amerine, et, al’, with the vegetables in-
volved in the analysis as blocks and the bl blanching conditions as treat-
ments. When the variance ratio (F value) calculated exceeded the
tabular F values at the one or five percent level of significance, mul-
tiple range tests could be used to determine significance due to indivi-
dual blanching for specific vegetables.

The statistical evaluation of organoleptic evaluation of canned green
bean samples was made by the investigators at Oregon State University
who conducted the test. These data were analysed by analysis of vari-
ance and the Least Significant Difference (LSD) at the five percent
probability level. A similar statistical evaluation was made of the re-
sults of organoleptic panel evaluation of samples of frozen corn-on-cob.

ECONOMICS

The cost of blanching using a new system such as hot-gas is a critical
factor in any decision to replace currently used equipment. Therefore,
a serious attempt was made in this study to gather information on which
to base cost estimates of commercial scale equipment for hot-gas,
steam, and hot-water blanching. The information on capital costs and
space requirements was obtained from suppliers or potential suppliers
of commercial scale equipment. The first cost ($) and space require-
ments (m2) for commercial steam and hot-water blanchers were:
25,000, 46.65; 15,000, 46.40; 20,000, 45. 13; 30,000, 55.14; and
8685, 15.50 for green beans, corn-on-cob, beets, spinach, and green
peas, respectively.

The operating costs were estimated from power usage, steam usage,
water consumption, and public utility fee schedules for a commodity be-
ing blanched in a unit of approximately five kkg or 5.5 ton/hr capacity.
Actual measured energy use during hot-gas blanching was one basis for
part of the estimate using appropriate scale-up factors.

Annual fixed costs were the sum of amortized first cost, space rent,

taxes, insurance and maintenance. Amortization was defined as the
capital recovery factor (crf) with 7 per-cent interest for a five year (yr)

-21-


The next product evaluation was made by examination of samples of
hot-gas blanched material which had been prepared and preserved
under commercial conditions. It was this examination which was the
basis of approval by plant management for the long duration runs.
The examination was made by running routine quality control exami-
nation and additional subjective testing for color, flavor, and texture
using commercial line samples as a basis for comparison.

Samples of raw, hot-gas blanched and commercially blanched vege-
tables were frozen using solid carbon dioxide, shipped frozen, and
stored frozen until vitamin and mineral analysis could be conducted
in the Berkeley, California and St. Louis, Missouri laboratories,
Samples were analysed for the vitamins and minerals expected, from
published compositional data, to occur at significant levels in each
of the five vegetables studied. The determinations of vitamin and
mineral content were made according to the Eleventh Edition of the
"Official Methods of Analysis of the Association of Official Analyti-
cal Chemist", Horwitz!90,

The selection of vitamins and minerals for analysis was based on three
types of data:
a) Tabulations of vitamin and mineral content of raw.
and processed vegetables, Watt and Merrill!}, Orr},
b) Official tabulations of Recommended Daily Dietary
Allowances, National Research Council 13,
c) Per capita consumption of processed vegetables, Judge!4,

In general, a vitamin or mineral was included in the analytical schedule
if a 100 gram (g) portion of a specified vegetable contained 10 percent
or more of the maximum recommended daily dietary allowance,
(MRDA). In those cases where all vitamins and minerals were below
the 10 percent figure, a combination of the percentage contribution to
the MDRA and the per capita consumption were used to make the
selection,

The vitamin and mineral testing schedule used in this study is tabu-
lated in Table 1.

-17-


APPENDIX Q (continued).

CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER

WASTEWATER

Dump water =
Total COD =

ss

Steam condensate =

Water overflow =

Dump water =
Total SS =

4-19-73
BOD

Steam condensate =

Water overflow =

Dump water =

Total BOD =

COD

Steam condensate =

Water overflow =

(5050) (16, 980) _
(108) *( 64)

(230) (52,800) _
(108) * (ea)

(12) _ (282,200) _
(70°) * ("64

(190) (16, 980)
(10) * (64)

(2740) _ (52, 160) _
(10°) * (67.8 ) >

(70) _ (265,120) _
(106) *(~ 67.8 )~

(3390) _ (16, 980) _
(10°) *( 67.8)

(3160) | (52,160) _
( 10°)" ( 67.8 )

(120) _ (265, 120)_
(10%) * (67.8 )

-100-

1.3 kg
5.0 kg/kkg

0.19 kg
0.05 kg

0.05 kg
0.29 kg/kkg

2.1 kg
0.27 kg

0.85 kg
3.2 kg/kkg

2.4 kg

0.47 kg


used to cool the hot-gas blanched corn was not collected and, therefore,
its contribution to wastewater volume and BOD content was unknown.

Table 6. WASTEWATER VOLUME AND CHARACTERISTICS FOR
HOT-GAS BLANCHING OF CORN-ON-COB

Sampling Wastewater Weight BOD, cop, Ss,

date volume, 1 blanched, mg/1 mg/l mg/1
kkg

9-18-72 a.m. 26. 42 0. 872 13500 24900 2640

9-18-72 p.m. 60, 5% 0.872 14200 23700 2920

9-19-72 a.m. 52. 9% 0.872 15100 24500 2350

9-19-72 p.m. 52. 9% 0.872 16500 26400 2680

9-20-74 a.m. 37. gb 0.545 14200 23000 1200

* Collected during eight hr of operation.
> Collected during five hr of operation.

The wastewater volume and characteristics for steam condensate from
commercial corn-on-cob blancher are tabulated in Table 7; additional
data are tabulated in Appendix F.

Table 7, WASTEWATER VOLUME AND CHARACTERISTICS FOR
STEAM CONDENSATE COMPOSITE SAMPLES FROM
COMMERCIAL BLANCHER FOR FROZEN CORN ON-COB

Sampling Average Total Total BOD, COD, Ss,

date feed rate, weight volume, mg/l mg/l mg/l

ears*/min blanched, 1
kkg

9-18-72 a.m. 69 9.95 960 15600 21700 2000
9-18-72 p.m. 66 9.69 677 13800 20600 740
9-19-72 a.m. 66 9.56 919 13100 20100 1300
9-19-72 p.m. 76 11.0 1058 14200 22700 1880
9-20-72 a.m. 98 15.5 1150 13800 21800 3190

a Ave. weight of corn ear before blanching was 0. 303 kg (0. 667 1b).
Composite samples prepared from equal volumes of each of four grab

-29-


parts (beet-hair roots, beet stems, corn silk, etc.). These sticking
pieces tended to stay on the belt and gradually dry out and caramelize
as the belt recycled through the heated zone. The sticking pieces did
not fall off the belt to contaminate freshly blanched vegetables. There
was no difficulty experienced in cleaning the wire mesh conveyor belt
with small volumes of water after several hr of continuous operation.
The hot-gas blancher did not present any unusual maintenance problems
during the period of operation.

The quality of final products from hot-gas blanched vegetables was a
major concern in this study. The quality evaluation of products from
hot-gas blanching was made at three stages. The first stage was sub-
jective examination of freshly blanched material by experienced indus -
try persons. A combination of appearance, feel, taste, and color
change was used to decide if a sample was adequately blanched. After
passing this first screening test, blanched samples were preserved,
by use of commercial equipment, as canned or frozen final products.
The preserved samples were given a complete quality control exam-
imation using objective tests and were also evaluated subjectively for
color, flavor, and texture differences by a group of technical and
management persons employed by the cannery. This evaluation was
the basis for approval to conduct long term runs with hot-gas

material returning to the production line. The third stage of evalua-
tion was controlled laboratory organoleptic panel comparison of sam-
ples and/or the sale of products through ordinary commercial chan-
nels. This latter form of evaluation was the only possible method for
spinach, beets, and peas where hot-gas blanched material was mixed
with commercially blanched material. For frozen corn-on-cob and
canned green beans, the hot-gas blanched portion was kept separate
and identified.

The very fact that every commodity studied was accepted for return to
production after hot-gas blanching demonstrated the utility of this
method with a considerable degree of confidence. The sale of beets,
spinach, and peas containing mixtures of hot-gas blanched and com-
mercially blanched material has resulted in no adverse consumer re-
sponse.

The organoleptic evaluation of green beans made by Oregon State Univ-
ersity, and tabulated in Table 23, indicates that there is no significant

-53-


fluoranthene was used arbitrarily as they ratio in the green bean sam-
ples could not be determined. Pyrene and fluoranthese being isomers,
they cannot be readily separated by thin-layer chromatography. One
ml of this standard solution was diluted to 10 ml and used as the fluoro-
meter standard.

APPENDIX B

SHORT DURATION HOT-GAS BLANCHING OF CUT GREEN BEANS

Run Kg/flight Product Temp, Residence Peroxidase Steam

no. total feed wt/kg °C time,sec reduction, % meter, %
wt, kg

GB 0.9

1 5.0 4.1 121 183 66 o*
GB 0.9

2 5.3 4.1 121 183 80 25%
GB 0.9

3 5.3 2.7 121 330 96 50%
GB 0.9 114-

4 5.5 4.9 119 144 100 (70 psig)>
GB 0.9 110-

5 8.8 9.3 117 82 96 (70 psig)>
GB 0.9 116-

6 9.5 9.5 118 82 98 (70 psig)?
GB 0.9 113-

7 8.6 8.5 121 82 99 (70 psig)?
GB 0.9 113-

8 5.9 5.7 121 92 96 (70 psig)?

-71-


SECTION V
EXPERIMENTAL RESULTS
BLANCHING AND WASTEWATER MEASUREMENTS

Green Beans

The results of short duration hot-gas blanching runs for cut green beans
are tabulated in Appendix B. The conditions used to prepare canned
samples of hot-gas blanched green beans for evaluation by management
prior to long duration runs are tabulated in Appendix C. The samples
prepared in Runs No. GB-41, GB-42, GB-44 were judged to be of
commercial quality and conditions used in these runs were established
for the forty hr of long duration operation. The conditions used for the
long duration hot-gas blanching of No. 4 sieve size, cut, green beans
were: a loading of 14.6 kg/m? (3 1b/£t2), a feed rate of 526-911 kg
(1160-2000 1b)/hr, an 80-96°C (176-205°F) operating temperature, a

77 sec residence time, and a 3 percent gauge setting on the meter

which gave 0.30 kg (0. 66 1b)/min of steam flow. The results from long-
term hot-gas blanching of cut green beans are tabulated in Table 2.

Table 2. LONG TERM HOT-GAS BLANCHING OF CUT GREEN BEANS

Date Hour of Feed rate, Temp, Peroxidase
operation® kg/hr °C reduction, %
8-15-72 0 0 -- --
1 737 85 17
2 730 87 17
3 -- 92 28
4 669 82 33
5 -- 91 20
6 567 91 18
7 -- 93 55
8 628 83 51
8-16-72 9 oo 87 19
10 671 84 27

-23-


APPENDIX M (continued)

GRAB SAMPLE CHARACTERISTICS FOR MAKE-UP WATER FROM
COMMERCIAL BLANCHER FOR GREEN PEAS (Volume = 570 1/hr)

Sampling Weight Sample BOD, cob, ss, pH

date blanched, type mg/1 mg/1 mg/1
(operating kkg

time)
5-10-73
(0-2 hr) 4.8 2hr 3990 7180 360 8.0
(2-4 hr) 4.9 4hr 3970 8170 220 7.5
(4-6 hr) 5.2 6 hr 8330 13800 290 7.1
(6-8 hr) 5.2 8 hr 4930 6390 280 8.0
5-11-73
(0-2 hr) 5.1 2hr 3590 5320 210 8.6
(2-4 hr) 5.2 4hr 4970 7100 180 8.1
(4-6 hr) 5.0 6 hr 7030 12100 190 7.5
(6-8 hr) 5.2 8 hr 5860 9770 210 7.6
5-12-73
(0-2 hr) 5.3 2hr 7750 11800 490 7.8
(2-4 hr) 5.1 4hr 7330 9540 370 8.0
(4-6 hr) 5.2 6 hr 3950 5850 200 8.6
(6-8 hr) 5.0 8 hr 6920 10600 380 8.2
5-14-73
(0-2 hr) 5.1 2hr 8010 11500 270 7.9
(2-4 hr) 5.3 4hr 9280 12400 200 7.8
(4-6 hr) 5.2 6hr 7210 8620 230 8.0
(6-8 br) 5.1 Shr 8230 13000 190 8.0

a Grab sample taken from blancher return surge tank after each 2 hr
of operation.

-89-


liquid waste.

A preliminary study of potential low-water volume methods of blanch-
ing was accomplished under U.S. Environmental Protection Agency's
Grant 12060 PAV, Ralls and Mercer. > Comparison of the results of
blanching seven vegetables with microwave, hot-gas, steam, and hot-
water blancher simulators revealed exceptional promise for the new
method of hot-gas blanching. The experimental unit used in the
laboratory study of hot-gas blanching (also called hot-air blanching

or dry-blanching) was the first of its kind known (to the authors) to

be constructed and tested. The unit conveyed raw vegetables through
an insulated rectangular chamber containing a natural gas furnace.
Most of the thermal energy received by the vegetable was due to the
heat content of combustion products and nitrogen. The hot gases
were circulated in the chamber by means of a large blower and by
convection currents. The cooled combustion gases were partially re-
circulated through the blower. Steam was injected at the top of the
chamber to improve heat transfer from the hot gases to the vegetables
and to reduce dehydration losses from the high-water content vege-
tables.

This preliminary study indicated that the volume of wastewater, the
pounds (1b) of chemical oxygen demand (COD), and suspended solids
(SS) per ton of vegetable blanched could be reduced 90 to 99 percent
when hot-water blanching was replaced by hot-gas blanching. There
were no significant differences in product quality, vitamin and
mineral retention, or internal can corrosion, among samples of
vegetables prepared with the four different blanching systems. An
estimate for commercial blanching using the four systems studied
led to the following total annual cost per ton of raw vegetable blanched:
microwave, $18.47; hot-gas, $3.39; steam, $2.21; and hot-water,
$2. 36 or $20. 30; $3. 73; $2.43; and $2.60 per kilo-kilogram (kkg),
respectively.

The initial study of hot-gas blanching was conducted in the National
Canners Association (NCA) Laboratory in Berkeley, California. The
laboratory study had several limitations; the most serious of which
was the requirement of long transport distances [322 to 1609 kilo-
meters (km) (200 to 1000 miles)]and excessive holding times (8 to

-4-


APPENDIX B

(continued).

SHORT DURATION HOT-GAS BLANCHING OF CUT GREEN BEANS

Run Kg/flight Product Temp Residence Peroxidase Steam

no. total feed wt/kg °C time,sec  reduction,% meter, %
wt, kg

GB 0.9 103-

9 9.6 9.4 107 82 98 (85 psig)

GB 0. 45 110-

10 8.5 8.4 116 73 99 (80 psig)

GB 0.9 110-

ll 8.9 8.6 118 73 98 (80 psig)»

GB 1.4 llo-

12 9.0 8.9 116 73 98 (80 psig)>

GB 1.8 110-

13 9.5 9.5 116 73 96 (80 psig)?

GB 1.8 107-

14 12.3 11.3 113 73 97 (60 psig)?

GB 1.8 116-

15 9.1 9.0 118 73 96 (50 psig)

GB 1.8 113-

16 10.2 10.0 116 73 99 (70 psig)>

GB 1.8 110-

17 9.3 9.2 116 73 98 (40 psig)?

GB 1.4 110-

18 10.5 10.5 116 73 99 (40 psigy®

-72-


APPENDIX D (continued)

WASTEWATER VOLUME AND CHARACTERISTICS FOR MAKE-UP
WATER OVERFLOW GRAB SAMPLES FROM COMMERCIAL
BLANCHER FOR CUT GREEN BEANS

Sampling Volume, BOD, CoD, ss, pH

date 1 mg/l mg/1 meg/1
(operating

time)
(2-4 hr) 227 7760 15500 1560 5.6
(4-6 hr) 133 7610 15500 1820 5.0
(6-8 hr) 64 10500 13400 1870 5.3
8-16-72
(0-2 hr) 133 7500 13000 1640 5.1
(2-4 hr) 72 7820 13300 1680 5.4
(4-6 hr) 57 7660 13100 1840 5.2
(6-8 hr) 144 4940 8320 910 5.4
8-17-72
(0-2 hr) 91 1820 3120 140 6.4
(2-4 hr) 104 2610 4780 550 6.5
(4-6 hr) 76 2040 3720 870 6.2
(6-8 hr) 68 6630 11000 610 6.1
8-18-72
(0-2 hr) 91 2390 4470 390 6.2
(2-4 hr) 64 4530 8380 670 6.0
(4-6 hr) 68 1300 2500 210 6.2
(6-8 hr) 80 --- o--- -- --
8-19-72
(0-2 hr) 83 4430 7390 650 6.0
(2-4 hr) 64 4020 6780 800 6.1
(4-6 hr) 49 4790 8080 1020 5.9
(6-8 hr) 76 4300 7000 820 6.1

-78-


ACKNOWLEDGMENTS

We express our sincere appreciation to the EPA's Kenneth A. Dostal
and Harold W. Thompson for many helpful suggestions during plan-
ning, data collection, and reporting of results for this project.

We thank Michael T. Soderquist and his colleagues at Oregon State
University for the BOD, COD, and SS determinations on wastewater
samples collected during experimental work at Corvallis.

The in-plant operations would not have been possible without the
permission and constant advice and assistance of management, pro-
duction, and technical persons at two food processing plants. Al-
though it is not possible to acknowledge by name the large number
of persons who made direct contributions to the installation, opera-
tion, and product evaluation phases of the in-plant work, a number
of key persons must be mentioned. At Tillie Lewis Foods, Inc. in
Stockton, California, the following persons were extremely help-
ful: Harry Rosen, Rex Defenbaugh, Clair Weast, Max Nicholson,
Andy Dillman, Walter Hein, Hugh Gartin, Don Krull, Frank
Yoneshiga, Chuck Fettie, Mary Wong, Jack Mays, and Jackie
Brewer, At Agripac, Inc. (Salem, Eugene, and Corvallis, Oregon),
Ed Pitkin, George Henken, Alton McCully, Donald Walker, Gary
Lewis, Robert Isaac, and Gene Parrish were instrumental in the
accomplishment of the in-plant blanching studies.

Many of the Oregon State University faculty provided advice and
direct assistance to the work in Corvallis, especially Darrell
Beavers, Robert Cain, Howard Milleville, Lois McGill, and
Michael Soderquist.

We thank Magnuson Engineers, Inc. of San Jose, California for
loaning us pieces of ancillary equipment during spinach blanching.

The following temporary employees of the National Canners Asso-
ciation were responsible for the operation of the hot-gas blancher,
sample collection, and sample analysis: Mark Zinnecker, Rich
Lane, Douglas Hommick, James Reiman, Holly Karnath, and

Nancy Howard.
-vii-


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

1 RLPORT NO. om 3, RECIPIENT'S ACCESSIONNO.
EPA-660/2-74-091
[a TITLE ANDSUBTITLE OS 5. REPORT DATE
CONTINUOUS IN-PLANT HOT-GAS BLANCHING December _1974
OF VEGETABLES ls. PERFORMING ORGANIZATION CODE
7. AUTHOR(S) (8. PERFORMING ORGANIZATION REPORT NO.
Jack W. Ralls, and Walter A. Mercer
D~2647
I. PERFORMING ORG \NIZATION NAME AND ADDRESS 10, PROGRAM ELEMENT NO,
National Canners Association 1BB037
Research Foundation 11. CONTRACT/GRANT NO.
1950 Sixth Street
Berkeley, California 94710 S-800250
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT ANO PERIOD COVERED

Final: 6-12-72 to 9-31-73

Pacific NW Environmental Research Laboratory
National Environmental Research Center
Corvallis, OR 97330

14, SPONSORING AGENCY CODE

16, SUPPLEMENTARY NOTES,

16. ABSTRACT

An experimental hot-gas blancher was operated in two food processing plants using
green beans, corn-on-cob, beets, spinach, and green peas. A side stream of
commercially prepared vegetables was hot-gas blanched and returned to the production
line. Electrical, gas, and steam flow meters were used with the hot-gas blancher
to obtain data for operational cost estimates.

Wastewater samples were collected from the commercial blancher and the hot-gas
blancher for each commodity studied; these were measured for volume and analyzed
for BOD, COD, SS and pH. Comparisons were made of reductions in wastewater
volume, BOD, COD and SS when steam or hot-water blanching were replaced by hot-
gas blanching. For beans, spinach and peas these reductions were 91 to 99 percent.
Operational costs were higher for hot-gas blanching than for steam or hot-water
blanching for all vegetables studied except for green beans which were slightly
lower. The flavor, texture, appearance, nutritional content and safety of hot-gas
blanched vegetables are generally equivalent to hot-water or steam blanched vege-
tables.

17. _. KEY WORDS ANDO DOCUMENT ANALYSIS

a ESCRIPTORS Ib. IDENTIFIERS/OPEN ENDED TERMS |c. COSAT! Field/Group
Blanching, vegetables, food processing, Freezing, canning, food
wastewater, reduced waste generation, preservation

hot-gas blanching

78 DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report} 21, NO. OF PAGES
Release Unlimited. Available through
Government Printing Office, Wash., D.C. 20. SECURITY CLASS (This page) 22. PRICE

EPA Form 2220-1 (9-73)

tt US GOVERNMENT PRINTING OFFICE 1974-697-757/70 REGION 10


APPENDIX C

PREPARATION CONDITIONS AND QUALITY EVALUATION OF
CANNED SAMPLES OF HOT-GAS BLANCHED GREEN BEANS

Run Can Brine Exhaust Headspace Quality
no. size temp, box temp, vacuum, evaluation
ae °c cm, Hg
GB 303 88 85 17.8 Excessive
18 sloughing
GB 303 82 80 15.3 Excessive
26 sloughing
GB 303 88 -- 12.7 Moderate
29 sloughing
GB 303 88 -- 12.7 Moderate
30 sloughing
GB 303 86 -- 15.3 Moderate
31 sloughing
GB 303 85 -- 12.7 Good flavor,
34 little sloughing
GB 303 82 74 12.7 No
36 sloughing
GB 10° 77 74 12.7 Too long
39 hold before
retorting
GB 10 60 74 10.2 Good flavor
40 but under-
blanched

-76-


APPENDIX R

COST ESTIMATE FOR COMMERCIAL PIPE BLANCHER AND HOT-

GAS BLANCHER FOR GREEN PEAS

Cost Estimate for Commercial Pipe Blancher
(2.73 kkg (3 tons)/hr capacity]

First cost (FC) = $8685.00

Annual fixed cost
Amortization = FC x crf (7%, 5 yr = 0.24389)
Space rent
Taxes [ $5. 00/$100 assessed value (25% of FC)]
Insurance (0. 2% of assessed value)
Maintenance (1% of FC/yr)

Total

Hourly fixed cost (1800 hr/yr)
Hourly operating costs

Electrical power
Steam

Water

Waste disposal
Labor

Hourly fixed cost
Hourly operating cost
Total hourly cost
Cost per kkg blanched

Cost Estimate for Commercial Hot-Gas Blancher

[5 kkg (5.5 tons)/hr]

First cost (FC) = $100,000.00

-102-

=$ 2118.18

2000. 00
108. 50
4,34
86. 85

$ 4317. 8?/yr

$

2.40/hr

0. 220
1.200
0. 016
0. 092

2.600

4.13/hr
2.40

4.13

6.53
2. 39/kkg


APPENDIX K (continued)

CHARACTERISTICS OF WASTEWATER FROM COMMERCIAL
SPINACH BLANCHER (1972)

Date Sample type coD, ss, pH
mg/l mg/1

SC-3.5H 3550 140 7.1

SC-4. 5H 4450 140 71

SC-5. 5H 4120 120 7.1

SC-6. 5H 4330 160 7.1

a WO-OH = water overflow at zero hr.
b SC-1H = steam condensate at one hr.

APPENDIX L

SHORT DURATION HOT-GAS BLANCHING OF GREEN PEAS

Run Feed Product Temp, Residence Steam Peroxidase
no. wt,kg wt,kg °C time,sec flow reduction, %
kg/min
TLFP-1 15.1 15.1 127-138 90 1.0 17
TLFP-2 9.6 8.8 121-132 90 1.0 25
TLFP-3 9.1 8.0 136-143 90 1.0 92
TLFP-4 9.1 7.9 136-154 110 2.0 99
TLFP-5 9.1 7.8 108-116 150 2.0 99
TLFP-6 9.1 8.0 119-143 102 2.0 99
TLFP-7 22.7 20.4 118-127 110 2.0 99
TLFP-8 9.1 8.0 127-143 105 1.0 99
TLFP-9 13.6 12.6 138-152 105 1.0 100
TLFP-10 9.1 8.6 143-149 107 1.0 99
TLFP-I1 22.7 22.2 138-146 106 1.0 99
TLFP-12 9.1 8. 143-149 107 1.4 99
TLFP-132 product canned 110-132 106 0.6 18

~87-


An observation made by technicians at Oregon State University, who
were preparing taste-panel samples of canned green beans held at
38°C (100°F) for three mo, has led to a more detailed study of the ex-
tent of internal can corrosion by Agripac, Inc. and their container
supply company. Sets of ten No. 10 cans each of hot-water and hot-
gas blanched green beans were opened at 12°C (54°F) after five mo of
warehouse storage. The extent of corrosion was rated from visual
inspection by experienced persons from a container supply company
on a scale of 1 = no corrosion and 10 = detined completely. The set
of hot-water blanched bean cans showed an average corrosion number
of 4.5 compared to a corrosion number of 2.3 for cans used for hot-
gas blanched beans.

If the extent of corrosion continues to be lower in hot-gas blanched
green bean cans, a considerable saving in container costs could help
to justify commercial use of hot-gas blanching.

Examination of cans used to store hot-gas and hot-water blanched
green beans for six mo at 38°C (100°F) was made by Oregon State
University with the following results:

‘When examined immediately after opening, there
appeared to be very little difference in the black

film on the insides of the cans. Some people thought
that the hot-gas cans were not quite so black, but

the difference was so small as to be questionable.
Close examination of the surface of the cans showed
that the control cans appeared to be quite extensively
detined. After setting in the laboratory for a few
days, the control cans showed quite extensive inter-
nal rusting, and the hot-gas cans only a small amount
of rusting, indicating that there was more detinning on

on the controls than in the hot-gas cans,'"! (Beavers!5)
COMPARISON OF COSTS OF BLANCHING SYSTEMS

In any consideration of new processing technology, the cost of opera-
tion per unit of production is one of the most important factors in de-
cision-making. It was possible to get exact operating costs for the
experimental hot-gas blancher by metering power and steam use.

-55-


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-51-


could be incorporated into commercial production and sold in the same
way as conventional products.

The next stage of the in-plant study was extended operation of the hot-
gas blancher up to the planned period of forty hr whenever possible.

WASTEWATER MEASUREMENTS

The measurements made on wastewaters from the hot-gas blancher
and the commercial blanchers were designed to provide the basis for
comparison of the waste generating characteristics of these blanching
systems, The volume of wastewater produced during the blanching of
a measured quantity of vegetables was determined. For the hot-gas
blancher, the total volume of condensate collected from the single
drain of the blancher, during each eight hr of operation was measured
with a plastic graduated cylinder or a calibrated plastic pail. The
collection of the eight hr total volume wastewater from the hot-gas
blancher was accomplished with ice-water cooling whenever possible,

The method used for collection of wastewater samples from the hot-
gas blancher, with ice-water cooling, is shown in Figure 2.

To determine the volume of wastewater generated per unit weight of
vegetable blanched, it was necessary to measure the quantity of vege-
tables hot-gas blanched during every two hr period of operation.

Generally the weight of vegetables hot-gas blanched was calculated
from the constant loading used and the determination of the number

of flights of the conveyor belt loaded during different periods of opera-
tion. This method of determining the weight of material hot-gas
blanched was used for corn-on-cob and beets. In the case of hot-gas
blanching of cut green beans and spinach, gross and tare weights of
tote boxes or wheeled carts containing beans or spinach were used for
the determination of the weight of material blanched. Due to the
variability in maturity of green peas, it was necessary to change the
residence time frequently to get complete blanching. A constant load-
ing rate was used. The variable residence time accounted for vari-
able through put.

-13-


Table 19 (continued), HEADSPACE GAS COMPOSITION OF CANNED
VEGETABLE SAMPLES

Commodity Headspace Percent of

(blancher) volume, ml N2 COz Argon+0) H2

Spinach

(commercial) 40 88.5 4.3 5.3 1.9
(hot-gas) 146 87.6 10.7 1.7 0.0

Peas

(commercial) 10.9 89.8 7.4 2.8 0.0
(hot-gas) 13.4 92.5 5.1 2.4 0.0

@ Data not recorded.

The results of replicate analyses for vitamin content of raw, hot-gas
blanched, and commercially blanched vegetable samples are tabulated
in Appendix N.

The results of replicate analyses for mineral content of raw, hot-gas
blanched, and commercially-blanched vegetable samples are tabulated
in Appendix O. The average values found for nutrient content of vege-
table samples are tabulated in Table 20.

Table 20. NUTRIENT CONTENT OF RAW, HOT-GAS BLANCHED,
AND COMMERCIALLY BLANCHED VEGETABLES
(mg/100 g wet weight)

Commodity Nutrient Raw Hot-gas Commercially
blanched blanched
Green beans Vitamin A® -- 0. 34 0.32
Vitamin By, 0.08 0. 06 0.07
Vitamin Bp 0.07 0. 06 0. 06
Vitamin Bg 0.03 0. 03 0.05
Vitamin C 7.3 2.2 1.3

-42-


Table 23. RESULTS OF ORGANOLEPTIC EVALUATION OF CANNED
GREEN BEANS AFTER STORAGE AT 38° FOR THREE AND

SIX MONTHS
Mean Score
Factor Sample A Sample B Sample C Sample D LSD#@
evaluated (hot-water) (hot-water) (hot-gas) (hot-gas) (0.05)
3b gb 3b gb 3b 6h = 3b gb 3b gb
Appearance 6.40 6.45] 5.92 5.82 16.40 6. 90, 7.45 7,121.46 .43
Texture 6.22 6.25;7.02 6.82 16.77 6.37'7.00 6.72).49 .56
Flavor 5.65 6.10;6.75 6.35 | 6.30 5.71/6.05 5.92!.54 .56
; \
Overall 5.65 6.27'6.52 6.12 | 6.30 6.00/6.40 6.50!.49 .51

Desirability t
aSee footnote a of Table 22.
Pstorage times in mo.

i

Table 24. ORGANOLEPTIC PANEL EVALUATION OF FROZEN CORN-
ON-COB AFTER STORAGE FOR ONE MONTH AT -18°C

Factor Sample A Sample B® Sample C Sample D LSD
evaluated (steam) (hot-gas) {hot-gas) (steam) (0. 05)P
Appearance 7.18 6.40 6.50 7.08 0.55
Texture 5.80 5.26 5. 80 6.12 0.53
Flavor 6.40 5.52 6. 32 5.78 0. 60
Overall 6.08 5.12 6.02 5.72 0.55
Desirability

a It was noted that Sample B was a more mature, starchy corn than
the other three samples and this is reflected in the lower texture and
overall desirability score.

> See footnote a of Table 22.

A triangular set of commercially-blanched and hot-gas blanched spin-
ach from the 1972 season was presented to a panel of sixteen persons
(four replicates) after the cans had been stored for 10 weeks at room
temperature. In a total of 57 judgments obtained in four sessions (us-
ing a randomized presentation of the samples), 29 were correct (sig-

-46-


APPENDIX B (continued).

SHORT DURATION HOT-GAS BLANCHING OF CUT GREEN BEANS

Run Kg/flight Product Temp Residence Peroxidase Steam

no. total feed wt, kg oC time, sec reduction,% meter, %
wt/kg_

GB 1.6

39 1.7 12.0 85 77 22 3¢

GB 1.5 90-

40 12.0 12.1 91 77 -- 3°

GB 1.4 83-

41 13.2 13.0 91 77 34 3°

GB 1.4 84-

42 12.5 12.9 88 77 0 3°

GB 1.4 85-

43 12.0 12.2 88 77 7 3°

GB 1.4 87-

44 12.6 12.7 91 77 12 3°

a Steam flow meter rated at 0.95 kg (2.1 1b)/min at 100 percent of
scale.

b Steam pressure gauge reading made during temporary closing of
inlet steam valve.

c Steam flow meter rated at 9.5 kg (21 1b)/min at 100 percent of
scale.

-75-


possible with hot-gas blanching. The waste generation comparison
should also provide a model into which new data could be substituted
for the reported data to allow a comparison to be made between a
specific commercial blancher and the hot-gas blancher.

The in-plant study gave access to product samples which could be
evaluated for quality on a direct comparison basis. The first quality
measurement planned was the effect of the blanching treatment received
on the level of nutrients in the blanched samples of vegetables. The
retention of nutrients during food processing is receiving considerable
attention at the present time due to intense public concern with nutri-
tion and nutritional labeling. The nutrient retention in vegetables
which are hot-gas blanched must be at least equivalent to that in vege-
tables from the blanching system being considered for replacement.
The cost of preparing labels for food producers listing nutritional in-
formation is so large that changes in nutrient content due to hot-gas
blanching would be the basis for rejecting its use. Therefore, for
decision making reasons it was important to determine the percentage
change in the nutrient content of raw vegetables due to hot-gas blanch-
ing. A comparison of nutrient retention between commercially blanch-
ed vegetables and hot-gas blanched vegetables is important as a basis
for judgements on the degree of differences to be expected.

Assuming that no substantial differences in nutrient content are found
due to hot-gas blanching, the next product quality factors of concern
would be flavor, texture, and appearance. The ideal basis for com-
parison of the effect of blanching on these quality factors would be
using preserved samples from all hot-gas blanched product compared
with regular commercial production line samples from similar lots of
vegetables prepared on the same day. The experimental plan was de-
signed to provide these kinds of samples whenever possible. It was
recognized that if the output of the hot-gas blancher was low, it would
be necessary to blend hot-gas blanched product with commercially
blanched product to avoid loss of commercial production capacity. In
the event that blending of the two types of blanched materials was
necessary, consumer reaction to lots of such product would be used
for quality evaluation. For commodities where it was possible to pre-
serve all hot-gas blanched material, direct testing against an equiva-
lent commercial sample was possible.

-8-


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-50-


No.

10.

ll.

12.

TABLES

Page
Schedule of Analysis for Vitamins and Minerals 18
Long Term Hot-Gas Blanching of Cut Green Beans 23

Wastewater Volume and Characteristics for Hot-Gas
Blanching of Green Beans

Wastewater Volume and Characteristics for Make-Up
Water Overflow Composite Samples from Commercial
Blancher for Cut Green Beans

Long Term Hot-Gas Blanching of Corn-on-Cob

Wastewater Volume and Characteristics for Hot-Gas
Blanching of Corn-on-Cob

Wastewater Volume and Characteristics for Steam
Condensate Composite Samples from Commercial
Blancher for Frozen Corn-on-Cob

Long Term Hot-Gas Blanching of Beets

Wastewater Volume and Characteristics for Hot-Gas
Blanching of Beets

Wastewater Volume and Characteristics for Make-Up
Overflow Composite Samples from Commercial
Blancher for Beets

Long Term Hot-Gas Blanching of Washed Spinach

Moisture Content of Raw and Hot-Gas Blanched
Spinach

-iv-

25

26

27

29

29

30

31

32

33

35


Vitamin Content of Raw, Hot-Gas Blanched, and
Commercially Blanched Vegetables

Mineral Content of Raw, Hot-Gas Blanched, and
Commercially Blanched Vegetables

Vacuum, Headspace, Net Weight, Count, and Matur-
ity of Canned Green Peas

Calculations for Commercial Spinach Blancher
Wastewater

Cost Estimate for Commercial Pipe Blancher and
Hot-Gas Blancher for Green Peas

Calculation of Cost of Hot~Gas Blanching of Peas

Checklist for Measurements Necessary for Hot-Gas
Blanching Operation

-67-

Page
90

94

95

96

102

104

105


period and allowing no salvage value. Space rent was set at $129/m2.
Boiler space requirements were ignored since all units require steam.
Taxes were set at $5. 00/$100 of assessed value based on 25 percent of
first cost. Insurance cost was computed on the basis of 0.2 percent of
assessed value. Maintenance cost was calculated as 1.0 percent of
first cost/yr.

In calculating operational costs, actual energy usage for the experi-
mental hot-gas blancher was multiplied by a scale-up factor (5 kkg
divided by the ave. feed rate in kkg) and an energy cost factor. For
commercial blanchers, part of the estimated operational costs were
based on the no. of drive motors and their ratings, measured water
consumption, and measured BOD and SS content of wastewaters. Cost
of electrical power was based on $0. 035/kilowatt hr (kwh). Steam
costs were computed at a rate of $2.20/kkg. Water costs were com-
puted based on $0. 10/3785 liters (1) [1000 gallons (gal. )]. Waste dis-
posal was based on $0, 023/kg (0. 05/1b) for BOD and SS removal during
treatment. Cost of natural gas was computed on the basis of $0. 76
/28, 3m>(1000 £3), Labor costs were based on $4. 00/hr plus $1.20 in
benefits. Each blancher was assigned a half-time worker for operation.
Cost of operating the pipe blancher was based on water cost, heating
cost, power cost for circulation pumps, and dewatering screen-drive
motors.

The uncertainties of estimation made the cost estimate useful only as a
rough screening of economic practicability of a new blanching system
before more extensive collection of cost factors for specific application
are made.

-22-


Flavor - An attribute of foods, beverages, and seasonings resulting
from stimulation of the sense ends that are grouped together at the
entrance of the alimentary and respiratory tracts -- especially odor
and taste.

Make-up water - Water added to circulating water in a system to re-
place water lost by evaporation, leakage, or blowdown.

Panel - A group of people (observers, subjects, judges) comprising
a test population which has been especially selected or designated in
some manner.

Peroxidase - A class of enzymes which catalyze the reaction of mole-
cular oxygen with a substrate to produce a peroxide link in the altered
molecule.

Protein - Any of the complex nitrogeneous compounds formed in liv-
ing organisms which consist of amino acids bound together by peptide
linkages.

Quality - The composite of the characteristics that differentiate among

individual units of the product and have significance in determining
the degree of acceptability of the unit by the user.

Ranking - A procedure of arranging food products in order according
to some criterion and assigning consecutive integers (ranks) corres-
ponding to the order.

Sample - A specimen or aliquot presented for inspection,

Score - A value assigned to a specific response made to a test item.

Suspended Solids (SS) - Solids that either float on the surface of, or
are in suspension in, water, wastewater, or other liquids.

Taste - One of the senses usually limited to four qualities: saline,
sweet, sour, and bitter.

-65-


operational costs for corn-on-cob and beet blanching are due to the
light loading, long residence time, and high steam-injection require-
ments. The operational cost for hot-gas blanching of spinach is a
factor of two higher than hot-water blanching and the increased cost
could only be justified by offsetting savings in waste disposal costs.

It is expected that some reduction of cost for hot-gas blanching would
result from increased efficiency of a commercial-scale unit compared
to the experimental unit.

The most significantly different cost factor in comparing hot-gas
blanching with steam and hot-water blanching is in waste management
Hot-gas blanching may be more attractive economically in the next
few years as waste treatment costs increase as the national goal of
zero discharge of pollutants by 1985 is approached. The very small
volume of liquid effluent produced during the hot-gas blanching makes
it an excellent choice as part of closed-loop technology if this is
proven possible.

The cost of treatment will increase as the percent removal of BOD
and SS increases, For those processors discharging into municipal
treatment systems, an increase in treatment level will increase the
surcharges paid by the industrial discharger. It is likely that waste
management costs will increase substantially; this will make hot-
gas blanching economically more competitive with steam or hot-
water blanching for additional vegetable commodities.

There has been much publicity recently about the "energy crisis’.
There seems to be little doubt that fossil fuel energy sources will be
in short supply for the period of 1974 to 1980. The reasons for the
potential shortage of such fossil fuels as natural gas are the high-
rate growth of energy consumption (4 percent per year) and reduction
in the U.S. reserves-to-production ratio. The reasons for the latter
fact are complex, but deliverable supplies of natural gas are shrink-
ing and in a number of areas potential customers have been unable to
obtain supply commitments.

The predicted shortage of natural gas may cause potential users of
hot-gas blanching to postpone use of this new blanching system. For-
tunately, the hot-gas blancher operates with liquified propane as a
fuel. Under the allocation program in effect since May, 1974, food

-58-


warehouse counts of cans after retorting. Knowing the fill weight for
each can, the total weight of material after blanching (with the excep-
tion of material lost in hold-up and spillage) could be computed. This
method was used for determining the weight of cut green beans and
whole beets blanched commercially during specific time periods. No
hot-gas blanched beans were mixed in with commercially blanched
beans; the weight of beets hot-gas blanched and returned to production
was subtracted from the computed weight. The weight of corn-on-cob
blanched in the commercial steam blancher was determined from a
count of the no. of ears entering the blancher/min and the weight of an
average (ave.) ear. The ave. weight/ear was determined by weighing
several containers each holding a known no. of unblanched ears and
dividing the net weight of ears by the no. of ears.

The weight of spinach commercially blanched was determined from
scalehouse weights (gross and tare) of trucks unloading spinach dur-
ing the period of blancher wastewater monitoring. These weights
were incorrect to the degree to which the raw spinach contained debris
or unusable spinach leaves rejected during sorting or washing. It was
estimated that the wet spinach presented to the blancher weighed
about the same as the dry, raw, spinach containing small amounts of
stones, dirt, weeds, and overmature leaves.

The volume of wastewater added to the commercial hot-water blanch-
ers was determined by metering the make-up water line, or by mea-
suring the blancher liquid discharge by collection in calibrated drums
for specific time periods. Generally, the rate of wastewater from
the commercial hot-water blanchers was determined by collection
during a period of one to five min every two hr of operation of the hot-
gas blancher. In the case of the pipe blancher for peas, the extensive
foaming at the make-up water surge tank and drain made direct mea-
surements of volume inaccurate. It was determined by observation of
the complete pipe blanching system that the major source of make-up
water was the rinse water at the dewatering screen which delivered
commercially blanched peas to the conveyor belt feeding the can filler.
A measurement of the rate at which rinse water was sprayed on the
commercially blanched peas established the make-up water feed rate.

-15-


The commercial beet blancher which was monitored was a rectangular
tank 1,22 m (4 ft) by 0.71 m (2 ft 4 in.) by 9.18 m (30 ft), partially
filled with approximately 7560 1 (2000 gal.) of hot water. The blancher
was drained weekly after five days of operation during which time 273-
364 kkg (300-400 tons) of beets were blanched. The blancher was sit-
uated outdoors and it was observed that more steam was required on
cold days than on hot days. The steam condensate formed the addi-
tional water which was discharged from the overflow pipe. No water
was supplied to the blancher when it was in operation. The volume of
overflow from the blancher receiving the smallest sized beets was
measured on two days. The results of volumetric measurements and
wastewater characterization of the make-up water overflow (steam con-
densate) of the commercial hot-water blancher for beets are tabulated
in Table 10. Due to scheduling problems and the short processing
season for beets, it was not possible for NCA to directly sample blanch-
er dump water. For purposes of calculation, the values found for the
eight hr composite sample of 10-5-72 (BOD=19, 600 mg/1; and SS=340
mg/1) were used for the blancher dump water composition. The volume
of water corresponding to eight hr of beet blanching on 10-5-72 was
21.8/(319) x 7560 or 5171.

Table 10. WASTEWATER VOLUME AND CHARACTERISTICS FOR
MAKE-UP OVERFLOW COMPOSITE SAMPLES FROM
COMMERCIAL BLANCHER FOR BEETS

Sampling Weight Volume, BOD, CoD, ss,
date blanched, 1 mg/l mg/1 mg/1
kkg
10-5-72 21.8 1999% 14000 19600 340
10-6-72 1l.1 484 11400 16500 230
a

Composite sample prepared from equal volumes of each of the four
grab samples.

b Composite sample made up of equal volumes of the 2 and 4 hr grab

samples.

-32-


Dividing by 4.17 will convert 1/kkg to gal. /ton.

Dividing by 0.5 will convert kg/kkg to lb/ton.

Values for commercial blanchers included water overflow, steam
condensate, and dump water.

See Appendix Q for example of calculation.

Table 28. PERCENTAGE REDUCTION OF WASTEWATER VOLUME,
BOD, COD, AND SS DUE TO HOT-GAS BLANCHING OF

VEGETABLES
Percentage reduction
Commodity Wastewater volume BOD COD ss
Green beans 99.9 99.9 99.9 99.9
Corn 33.3 28.3 22.2 18.7
Beets (2.2) 47.5 56.5 37.0
Spinach 99.9 99.8 99.2 99.5
Green peas 94.2 91.4 90.0 93.0

a value in parenthesis is percentage increase.

hot-gas blancher used was an experimental design possibly quite diff-
erent from any future commercial unit.

The experimental hot-gas blancher was operated safely during a total
of approximately 300 hr of in-plant work. The natural gas furnace had
elaborate safety controls and the accumulation of gas, which would
represent the major hazard, was highly improbable. The combustion
of the natural gas was complete so the formation of carbon monoxide in
toxic amounts was highly unlikely.

There was no overt evidence of difficulty in sanitizing the hot-gas
blancher. The blancher was operated at a temperature above those
tolerant to the growth of microorganisms. There was some sticking
to the conveyor belt surface of small pieces of vegetables or their

-52-


Table 1. SCHEDULE OF ANALYSIS FOR VITAMINS AND MINERALS

Vitamins Minerals
Commodity A BB 3B, Bs C¢ Niacin Ca Mg P Fe
Green Beans Yes Yes Yes Yes Yes Yes Yes Yes Yes No
Beets No No YesNo No Yes No No Yes No
Corn No Yes Yes Yes No Yes No No Yes No
Peas No Yes Yes Yes Yes Yes Yes Yes Yes Yes
Spinach Yes No Yes No Yes No Yes Yes Yes Yes

Headspace gas analysis (by gas chromatography) of canned samples of
green beans, beets, spinach and peas was made as a measure of the
removal of oxygen from the tissues of blanched vegetables, Ralls and
Mercer3, The second type of estimation of the extent of tissue oxygen
removal was subjective examination of cans of cut green beans after
various storage times and temperatures. Canned samples of beets,
spinach, and peas were not stored long enough to show differences in
extent of internal can corrosion. Samples of green beans were stored
at 38 degrees Centigrade (°C) [100 degrees Fahrenheit (°F)] (accelera-
ted storage) for six months (mo), a condition which approximates the
longest expected storage life (18 mo) of cans in commercial distribution
at ambient temperatures. Results of examination of cans of green beans
stored in a warehouse for five mo were also made available by the Re-
search Director of the canning company in whose plant the cans were
packed,

The complete description of the method used for measuring levels of
polynuclear hydrocarbons is given in Appendix A. For this investiga-
tion, standards used were the polynuclear hydrocarbons: anthracene,
fluoranthene, and pyrene. It was not possible to introduce potentially
carcinogenic hydrocarbons such as benzo (a) pyrene into a food re-
search laboratory due to the extensive monitoring and safety protocols

-18-


APPENDIX J

VOLUME AND CHARACTERISTICS OF WASTEWATER SAMPLES
COLLECTED FROM HOT-GAS BLANCHER FOR SPINACH (1972)

Date/time Volume coD, Ss, pH
1 mg/1 mg/1
3-27-72
11:40 --- --- --- ---
12:40 p.m. 0.472 30500 5990 7.6
1:40 0.238 31800 2090 7.7
2:40 0.238 52400 7920 7.4
3:55 0.238 69000 6340 7.6
4:35 0. 238 68500 5590 7.4
5:10 0.238 67000 870 7.2
3-28-72
10:00 --- --- --- ---
11:00 0.026 194200 12340 7.7
12:50 0.15 201000 4360 7.6
1:35 0, 02 146900 5860 7.9
2:35 0.005 275800 10440 7.8
3:35 0.472 104000 1430 7.6
3-19-72
8:30 --- 6200 360 7.4
9:30 0.011 3300 810 7.4
10:30 0. 026 179500 10620 7.6
12:00 0.034 26900 1700 7.4
1:00 0.12 226900 6230 7.6
2:00 0. 053 42400 2530 7.7
3:00 0. 083 259500 6670 7.5

-85-


Table 16 (continued). LONG TERM HOT-GAS BLANCHING OF GREEN

PEAS
Date Hour of Feed rate, Temp, Peroxidase
operation@ kg/hr % reduction, %

2 233 107 99

3 288 107 99

4 232 99 99

5 259 107 99

6 273 99 99

7 268 99 99

8 277 99 99

5-12-73 9 490 132 99

10 286 116 99

1l 232 113 --

12 182 107 99

13 182 110 --

14 182 107 99

15 440 113 99

5-14-73 16 375 121 --

17 280 101 99

18 238 99 --

19 263 104 --

20 450 132 99

21 186 107 “-

22 184 107 99

23 273 110 --

24 248 116 99

25 408 113 --

26 182 110 99

27 477 132 99

28 279 113 --

29 284 110 99

306 277 107 99

2 The total volume of waste water collected (corrected for the volume
contributed by residual fluming water) at 0 to 8, 8 to 16, 16 to 24,
and 24 to 29 hr of operation was 30.5, 33.1, 32.6, and 18.11,

respectively.
-39-


APPENDIX E (continued)

SHORT DURATION HOT-GAS BLANCHING OF CORN-ON-COB

Run Kg/flight Product Temp, Residence Peroxidase Steam
no. total feed wt,kg Tor time, min reduction, % meter, %
wt ,kg
coc-l1 2.1
9.2 9.0 102 16.5 83 13
COC-12 2.1
10.0 9.6 104 16.5 95 10
COC-13 2.1
9.7 9.3 104 16.5 95 10
coG-14 2.1
9.8 9.5 107 15 97 15
coc-15 2.1
10.0 9.9 107 15 96 25
COC-16 2.1
9.8 9.5 110 17 b 23
coc-17 2.1
8.1 9.5¢ 102 12.8 gab 30
COc-18 2.1
9.0 9.3¢ 102 10 g2b 30
cOc-19 2.1
9.1 9,.7¢ 102 11.3 g5P 30
coc-20 2.1
9.5 10. 0¢ 102 12.5 78 30

-80-


of conveyor-drive motors, cost of make-up water, and estimates of
wastewater disposal costs.

The estimates of first cost for commercial scale blanchers was ob-
tained from commercial suppliers or potential suppliers. The first-
cost of hot-gas blanchers was based on cost of modules which could
be arranged in series to provide blanching conditions for each com-
modity. The required number of modules was computed from feed
rates observed during experimental hot-gas blanching. Table 30
summarizes the basis of computing first-cost of hot-gas blanchers
for various commodities.

Table 30. BASIS FOR ESTIMATING FIRST COST OF COMMERCIAL
SCALE HOT-GAS BLANCHERS

Commodity Average feed Scale-up Relative No. of First
rate*, kkg/hr factor? scale-up modules® cost,

factor $
Green beans 0.720 7 1 2 50,000
Corn-on-cob 0.109 46 6 12 255,000
Beets 0.105 48 7 14 285, 000
Spinach 0.158 31 4 8 185,000
Green peas 0. 336 15 2 4 100, 000

For experimental data, see Tables for long term blanching of each

commodity.

b See Experimental Plan (Economics) for basis of calculating scale-
up factors.

© Estimated cost/module: 1 to 5 @ $25,000/each; 5 - 10 @ $20, 000/

each; 10 - 20 @ $15, 000/each.

Only in the case of green bean blanching is the operation cost of hot-
gas blanching competitive with commercial blanching costs. The high

-57-


APPENDIX E (continued)

SHORT DURATION HOT-GAS BLANCHING OF CORN-ON-COB

Run Kg/flight Product Temp, Residence Peroxidase Steam
no. total feed wt,kg °C time,min reduction, % meter, %
wt, kg

cOoc-21 2.1
5 10.1¢ 104 12.5 97 30

Re}

COC -22 2.1

@

9.4¢ 104 12.5 93 30

a Steam flow meter rated at 9.5 kg (21 1b)/min at 100 percent of scale.
Catalase test negative.
© After cooling with water sprays.

APPENDIX F

WASTEWATER VOLUME AND CHARACTERISTICS FOR STEAM
CONSENSATE GRAB SAMPLES FROM COMMERCIAL BLANCHER
FOR FROZEN CORN-ON-COB

Sampling Feed rate Weight Volume, BOD, CoD, ss,

date ears/min blanched, 1 mg/l mg/1 mg/1
kkg
9-18-72 a.m.
(0-2 hr) 65 2.32 210 12500 19000 370
(2-4 hr) 78 2.83 190 14400 22100 733
(4-6 hr) 92 3.31 290 16800 24700 533
(6-8 hr) 4l 1.49 270 14200 20100 620

9-18-72 p.m.

{0-2 hr) 69 2.51 201 12800 19000 610
(2-4 hr) 62 2.35 213 14800 21100 630

-81-


Table 4. WASTEWATER VOLUME AND CHARACTERISTICS FOR
MAKE-UP WATER OVERFLOW COMPOSITE SAMPLES
FROM COMMERCIAL BLANCHER FOR CUT GREEN BEANS

Sampling Total Total BOD, CoD, ss, pH
date weight volume, mg/l = mg/1 mg/l
blanched, 1
kkg

8-15-72 12.9 882 8510 13900 1810 6.5
8-16-72 14,2 406 7070 11800 1520 --
8-17-72 17.6 339 3850 6600 530 --
8-18-72 9.8 303 2870 5280 470 --
8-19-72 11.3 272 4580 7720 810 --
Corn

The results of short duration experiments on hot-gas blanching of corn-
on-cob are tabulated in Appendix E. Corn-on-cob was the only com-
modity studied in this project which was marketed as a frozen product.

A dozen ears of corn from Run Number COC-20 were tagged and frozen.
The following day these ears were tested (with subjective examination)
by a group of Agripac, Inc. quality control specialists and compared
with commercially-blanched frozen ears of corn. The consensus of the
evaluation group was that the hot-gas blanched corn would be commer -
cially acceptable but had a distinctly different flavor. A decision was
made by Agripac, Inc. management that the forty hr run of hot-gas
blanching of corn-on-cob should proceed but that all product produced
must be tagged and segregated after freezing for further quality evalu-
ation after three mo of storage. A further condition was that the ears
of hot-gas blanched corn be cooled to a temperature as low as the
water-cooled corn on the commercial line before they were put into the
freezer. This latter condition was met by installing a second cooling
water spray manifold and using five min of spray cooling, five min of
draining, and a second five min of spray cooling. The internal temper-
ature in the cob of hot-gas blanched corn, under conditions of Runs 20-
22, was 66-71°C (150-160°F). After the cooling sequence described

-26-


SECTION II
RECOMMENDATIONS

Food processing equipment-supply companies should design hot-gas
blanchers of optimal performance for each individual commodity.

The commercial scale hot-gas blanchers should incorporate vibratory
conveyors to move vegetable pieces and to expose fresh surfaces for
more efficient and uniform heating.

The commercial scale hot-gas blanchers should be designed to take
advantage of natural convection currents above natural gas flames
with minimal assistance from blowers.

A commercial scale hot-gas blancher for cut green beans should be
installed in a food processing plant and should be compared to current
or previous experience with hot-water blanching.

Hot-gas blanching should receive careful consideration in new plant
installations where closed loop use of water is planned.

The overall consequence of accepting higher dehydration losses during
hot-gas blanching of vegetables prior to canning or freezing should be
more completely evaluated.


tabulated in Table 19.

Table 18. CHARACTERISTICS OF COMMERCIAL GREEN PEA PIPE-
BLANCHER DUMP WATER AND MAKE-UP WATER

Sampling Weight Sampling BOD, COD, ss, pH
date blanched, type? mg/1 mg/1 mg/l
kkg
5-8-73 20.4 DW 6920 9800 470 8.4
Wwo-C 4820 7040 210 8.4
5-9-73 21.2 DW 8250 11800 410 71
wo-C 5800 7040 290 8.2
5-10-73 20.1 DW 8890 13100 390 6.8
wo-cC 4650 7710 230 7.2
5-11-73 20.5 DW 4650 8170 220 7.4
WO-C 6180 10700 210 7.0
5-12-73 20.6 DW 4060 5000 210 8.8
WOo-C 6500 10400 310 8.1
5-14-73 20.7 WOo-C 7410 13600 190 8.1

&@ See footnotes a, c of Table 15.

Table 19. HEADSPACE GAS COMPOSITION OF CANNED VEGETABLE

SAMPLES
Commodity Headspace Percent of
(blancher) volume, ml N2 COz Argont02 H2

Green beans

(commercial) 119 90.3 hl 8.6 0.0
(hot-gas) 117 86.4 5.0 5.2 3.4

Beets

(commercial) a 87.4 7.6 1.9 ol
(hot-gas) a 93.8 5.0 1.2 0.0

-41]-


SECTION I
CONCLUSIONS

Hot-gas blanching of thin or small piece-size vegetables (such as
spinach, cut green beans, or green peas) accomplishes the requisite
enzyme deactivation and tissue gas removal at practical loading rates
[10.7 to 14.6 kg/m2 (2.2 to 3.0 1b/ft2)]and residence times (77 to
240 sec).

Hot-gas blanching of large piece-size vegetables (such as corn-on-cob
and whole beets) requires long residence times (14 to 25 min) and high
steam usage [1.9 to 2.9 kg (4.2 to 6.3 1b)/min] to achieve adequate
blanching.

Costs for hot-gas blanching of vegetables are higher than for steam or
hot-water blanching. The fixed costs estimated for hot-gas blanchers
are 1.6 to 10.7 times higher than for hot-water blanchers. The
operating costs for hot-gas blanching are 0.75 to 5.8 times higher than
for conventional steam or hot-water blanching.

The flavor, texture, appearance, nutritional content, and safety of
hot-gas blanched vegetables are generally equivalent to hot-water or
steam blanched vegetables.


conveyor of the hot-gas blancher made direct weighings of samples of
washed and blanched spinach of questionable significance in determin-
ing actual weight changes due to blanching. During the long-term runs
in 1973, three samples each of raw and of hot-gas blanched spinach
were taken and moisture determinations made; the results are tabu-
lated in Table 12.

Table 12, MOISTURE CONTENT OF RAW AND HOT-GAS BLANCHED

SPINACH
Sample Moisture content, # %
Raw
1 91.7
2 91.7
3 91.5
Ave. 91.6

Hot-gas blanched

1 90.1
2 89.7
3 90.5
Ave. 90.1

2 Calculated on a wet weight basis.

The volume and characteristics of wastewater collected from the hot-
gas blancher during long term operation with washed spinach are tabu-
lated in Table 13. Additional date collected during the 1972 season are
tabulated in Appendix J.

The commercial spinach blancher monitored was a combination steam
and hot-water unit. The blancher had a 1.52 m (5 ft) wide wire mesh
belt which conveyed washed spinach through a steam section 3.05 m

(10 ft) long and a hot-water section 12.2 m (40 ft) long and 0.914 m

(3 ft) deep. The blancher had a rated capacity of 9. 09 kkg (10 tons)/hr.
For three 22.5 hr operating periods in 1972, the weight of spinach
loaded into the blancher was 149, 174, and 164 kkg, respectively. The

-35-


Figure 2. Collection of steam condensate sample
from the hot-gas blancher

The sampling of wastewater from commercial blanchers was designed
to determine the total wastewater generated during eight hr periods of
commercial operation. The wastewater measured consisted of total
steam condensate in the case of the corn-on-cob blancher which was
collected at four drainage points, combined,and the volume measured
in calibrated drums every two hr.

Combined make up water overflow and dump water for the green bean,
beet, spinach, and green pea blanchers were measured.. Rarely did

the dumping of commercial hot-water blanchers occur at eight hr in-
tervals; to put wastewater data on a comparable basis, the volume of
dump water measured was divided by the number (no. ) of eight hr
periods comprising the hr of use of the blanchers between dumpings.

The method used to determine the weight of vegetables blanched in the

commercial blancher being monitored varied with the commodity under
study. The no. of cans packed in any given time period from material
blanched during that time in a specific blancher was obtained from

-14-


The experimental plan called for evaluation of flavor and appearance
by an organoleptic panel. These panels are used routinely in the food
industry to establish differences in quality among food samples,
Amerine, et.al.’ The laboratory study of hot-gas blanching had in-
dicated a weight loss in blanched material due to dehydration. There
was also an indication that steam injection could reduce dehydration
losses. Loss in weight by dehydration is of direct consequence for
preservation by freezing since the product value is usually based on
weight. The only frozen product used in this study, corn-on-cob, was
sold by count so weight losses due to blanching were not of critical
concern. There is a possibility that spray cooling of hot-gas blanched
vegetables destined for frozen preservation would cause replacement
of a substantial part of the water lost by dehydration; investigation of
this point was not part of the experimental plan. Some loss of mois-
ture content during hot-gas blanching of vegetables could be accomo-
dated in products to be preserved by canning. It would be expected
that the partially dehydrated vegetables would regain water from the
packing medium. The experimental plan called for control of the loss
of water through dehydration by injection of steam. In those cases
where some dehydration of vegetables took place, the experimental
plan called for determination of the change in moisture content and
evaluation of the degree of rehydration in the can.

The most important function of blanching for vegetables to be pre-
served by canning is removal of tissue gases. If not properly re-
moved during blanching, gases released by the vegetable tissue can
decrease the vacuum and contribute to the internal corrosion of the
container by increasing the oxygen content in the headspace gases.
Direct measurement of the gas composition of vegetables is very
difficult due to sampling and gas displacement problems. It is
possible to determine the degree of gas removal during blanching by
an indirect method of headspace gas analysis. The experimental plan
included analysis of cans from hot-gas blanched and commercially
blanched material for composition of gases in the headspace as an
indication of the effectiveness of hot-gas blanching in removing oxygen
from vegetable tissues.

Another indicator of incomplete removal of gases from vegetables dur-
ing blanching is accelerated internal can corrosion. Examination of

-9-


No.

13.

14,

15.

16.

17.

18,

19.

20.

2l.

22.

23.

TABLES

(continued)

Wastewater Volume and Characteristics for Hot-
Gas Blanching of Washed Spinach

Steam Condensate and Make-Up Water Overflow
Rates for Commercial Spinach Blancher

Characteristics of Commercial Spinach Blancher
Dump Water, Steam Condensate, and Make-Up
Water Overflow

Long Term Hot-Gas Blanching of Green Peas

Wastewater Volume and Characteristics for Hot-
Gas Blanching of Green Peas

Characteristics of Commercial Green Pea Pipe-
Blancher Dump Water and Make-Up Water

Headspace Gas Composition of Canned Vegetable
Samples

Nutrient Content of Raw, Hot-Gas Blanched, and
Commercially Blanched Vegetables

36

37

38

40

4l

41

42

Levels of Polynuclear Hydrocarbons in Canned Green

Bean Samples

Results of Organoleptic Evaluation of Canned Green

Beans One Month After Canning

Results of Organoleptic Evaluation of Canned Green

Beans After Storage at 38° C for Three and Six

Months
-v-

44

45

46


APPENDIX T

CHECKLIST FOR MEASUREMENTS NECESSARY FOR HOT-GAS
BLANCHING OPERATION
(Data to be recorded in bound notebook as taken)

Commodity
Location
Date

Starting time

Product feed Blanched product weight
(every 2 hr)

Rate (every 2 hr)

. 2 hr grab sample volume + COD

Conveyor drive
sample

Setting

. Commercial (refrigerate)
Setting OT

8 hr wastewater volume + COD

Temperature, °F (hourly) sample

(or when significant change)
Commercial hot-gas

(ice-cooled)
Electrical meter #1
Start

Finish

Peroxidase sample, hourly
(hot-gas only)

Vitamin, mineral samples (1 ru
Electrical meter #2 ms mp. ( »)

Start Raw Commercial blanched
Finish hot-gas

Electrical meter #3 Finishing time

Start

Finish

Gas meter
Start
Finish
Steam flow meter
Start
Finish
-105-


SECTION VII
GLOSSARY

Acceptance - (1) An experience or feature of experience, charact-
erized by a positive (approach in a pleasant) attitude. (2) Actual
utilization (purchase, eating). May be measured by preferences or
liking for specific food item.

Analysis of Variance - A method of determining the significance of
differences in a group of averages of experimental observations by
partitioning of the total sum of squares and degrees of freedom, and
estimation of the standard deviation of the population by two or more
methods and a comparison of these estimates.

Appearance - The visual properties of a food, including size, shape,
color and conformation.

BOD - Abbreviation for biochemical oxygen demand. The quantity
of oxygen used in the biochemical oxidation of organic matter in a
specified time, at a specified temperature, and under specified con-
ditions.

COD - Abbreviation for chemical oxygen demand. A measure of the
oxygen-consuming capacity of inorganic and organic matter present
in water or wastewater.

Blanching - Heating a food to a temperature high enough to inacti-
vate enzymes present and to remove undesirable occluded gases and
contaminants.

Coding - Assignment of symbols, usually letters and/or numbers,

to test samples so that they may be presented to a subject without
identification.

Consumer - An individual who obtains or uses a commodity.

Enzyme - A catalyst produced by living cells which is protein in
nature.

-64-


which would have been required. The use of potentially carcinogenic
hydrocarbons was unnecessary for this study since it had been demon-
strated by Mukai, et.al4 that incomplete combustion of methane, pro-
pane or isobutylene always produces a mixture of anthracene, pyrene,
fluoranthene, benzo (a) pyrene, benzo (e) pyrene, and perylene in
relatively constant proportions. Therefore, detection of any signifi-
cant differences in the level of anthracene, fluoranthene, and pyrene in
hot-water and hot-gas blanched green bean samples would be presump-
tive evidence for the presence of benzo (a) pyrene.

A detailed evaluation of the quality of canned cut green bean samples
was made in the Sensory Evaluation Program of the Department of
Food Science and Technology at Oregon State University under the
supervision of Professor Lois A. McGill. The samples were tested
after storage at 38°C (100°F) for periods of one, three, and six mo,
The procedure used for preparing samples for panel evaluation varied
slightly for each storage period.

For samples stored one mo: The separate samples were brought to
71°C (160°F) and served in random numbered coded cups.

For samples stored three mo: One Number 10 can of each sample of
canned green beans was removed from 38°C (100°F) storage at

10:00 a.m. and allowed to stand at room temperature until tested at
2:00 p.m. For testing, a vacuum reading was taken on each can, the
cans opened, emptied into identical sized pans, heated to a rolling
boil, removed from the heat then served hot to the judges.

For samples stored six mo: One Number 10 can of each sample of green
beans was removed from 38°C (100°F) storage on March 12 and placed
at ambient temperature until tested at 2:30 p.m., March 13, 1973. For
testing, a vacuum reading was taken on each can, the cans opened,
emptied into identical pans, heated to boiling at 100°C (212°F) and held
at boiling temperature for ten min then removed from the heat and
served hot to the judges, The ten min boil was a precautionary mea-
sure as the vacuum readings were 3.0 inches (in. ) of mercury or less
on all four samples.

The Cregon State University panel consisted of forty staff members who
completed a ballot based on a nine point hedonic scale for appearance,

-19-


48 hours (hr)] before blanching the vegetables. The long holding times
between commercial preparation of the vegetable samples for blanch-
ing and the actual laboratory blanching were particularly serious for
green peas (shelled), cut green beans, and asparagus (trimmed). The
changes which took place in these commodities during the holding per-
iod before blanching made the significance of some data uncertain. The
changes in corn (shipped in husks), beets, pumpkin (shipped whole),
and spinach (whole leaf) during the holding periods were not large
enough to influence the significance of the data collected on these
commodities. The laboratory study was limited to short-duration
blanching runs due to raw vegetable cost; for long-duration blanching
runs it would have been necessary to waste large quantities of whole-
some food since the laboratory equipment for canning and freezing of
vegetables could not handle the blancher's output. A third limitation
of the laboratory study was the lack of direct measurement of electri-
cal, gas, and steam usage for more precise cost estimates.

The next step in testing the commercial utility of hot-gas blanching
was operation of the unit under conditions which would avoid the limita-
tions of the laboratory study. The decision was made to test the com-
mercial utility of the new processing system at a commercial process-
ing plant. With an in-plant installation, raw vegetables prepared for
commercial and experimental blanching would be identical and, there-
by, eliminate the impact of blanching time differences on the signifi-
cance of data collected. Assuming that the experimental unit could be
operated to produce blanched vegetables having acceptable commer-
cial quality, most of the blanched vegetables could be returned to the
commercial production line to avoid wastage of food. The in-plant
installation of a single experimental blancher would make possible, at
reasonable cost, the installation of electrical, gas, and steam flow
meters. Meter readings would supply information for operational cost
estimates. The in-plant study also would provide the opportunity for
the measurement of the volume and characteristics of waste waters
from commercial blanchers and comparison of these values with the
same wastewater values from the experimental blancher.

This report describes the results of a comprehensive study of hot-gas

blanching of peas, corn, spinach, beets and green beans attwo food
processing plants. The study was designed to develop information on

-5-


Table 2 (Continued). LONG TERM HOT-GAS BLANCHING OF CUT
GREEN BEANS

Date Hour of Feed rate, Temp, Peroxidase
operation@ kg/hr °¢6 reduction, %
ll -- 95 54
12 835 83 40
13 -- 80 83
14 -- 81 17
15 725 86 43
16 -- 84 42
8-17-72 17 709 83 51
18 709 96 44
19 763 82 35
20 -- 83 23
21 -- 80 19
22 758 83 26
23 -- 90 54
24 780 83 45
8-18-72 25 -- 83 37
26 763 80 0
27 -- 92 40
28 -- 83 44
29 -- 87 32
30 911 84 39
31 763 83 30
8-19-72 32 -- 80 27
33 526 83 70
34 -- 86 42
35 -- 82 33
36 763 83 37
37 -- 82 62
38 -- 89 23
39 681 82 33
40 -- 84 27
41 653 83 37

a Total volume wastewater samples collected from 0 to 8, 11 to 16, 24
to 32, and 32 to 40 hr of operation were 0.473, 0.113, 0.620, and
0.246 1. respectively, The 16 to 24 hr sample was spilled and lost.

-24-


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APPENDIX K

CHARACTERISTICS OF WASTEWATER FROM COMMERCIAL

SPINACH BLANCHER (1972)

Date Sample type CoD, ss, pH
mg/l mg/l

3-27-72 WO -OH* 260 50 7.8
Wwo-1H 160 70 7.7
WwoO-2H 270 50 7.7
Wo-3H 230 40 7.7
WO-4H 240 30 7.7
SC-OH 4040 140 7.0
sc-1H> 4120 120 7.0
SC-2H 4370 120 7.0
SC-3H 4330 130 7.0
SC-4H 4450 80 7.0

3-28-72 WO-OH 510 70 7.5
WO-1. 5H 300 70 7.6
WwO-2H 480 170 7.6
WoO-4H 330 140 7.6
wo-5. 6H 250 90 7.7
WO-6H 300 90 7.7
SC-OH 4120 110 71
SC-1. 54H 4080 70 7.0
SC-2H 4080 120 71
SC-4H 3880 100 71
SC-5.6H 3960 60 2.7
SC-6H 3960 80 7.7

3-29-72 WO-OH 270 60 7.0
Wo-1H 290 70 6.9
WO-3. 5H 340 130 6.9
wo-4, 5H 270 60 6.9
WO-5. 5H 430 170 6.8
wo-6. 5H 340 100 6.8
SC-OH 4410 140 7.1
SC-1H 4690 110 71

-~86-


all the factors which would concern potential commercial users of hot-
gas blanching. The major considerations treated in the study were
operational costs; wastewater generation; wastewater characteristics;
final product safety, quality, and nutritional content; and internal can
corrosion,

One safety aspect of the final product was not recognized until after the
study was underway. This was the potential for the occurrence of
polynuclear hydrocarbons in vegetables blanched by the hot-gas unit.

It is known that oxidation of any fuel can produce a mixture of poly-
nuclear hydrocarbons during incomplete combustion, Mukai, et. al.

Some of these compounds are known to produce cancer in experimental
animals, Bryan and Lower.° Although there is no definitive evidence
that oral ingestion of trace amounts of polynuclear hydrocarbons causes
cancer in humans, any food shown to contain significant amounts of
known animal carcinogens would be subject to question by the Federal
Food and Drug Administration. Therefore, a study of the polynuclear
hydrocarbon content of samples of hot-water and hot-gas blanched cut
green beans was conducted to determine if the potential for this con-
tamination existed.


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(8€0 °0) ($50 °0)
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(100) (10°)
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-92-


APPENDIX Q (continued)

CALCULATIONS FOR COMMERCIAL SPINACH BLANCHER
WASTEWATER

3-29-72
Total wastewater/8 hr = 180, 380
Weight of spinach (164) _
blanched = (22.5) *8* 58 kkg
Vol 8h. kkg/8 hr) = 180, 380
(Volume/8 hr)/(kkg/8 hr) . 3, 100 1/kkg
58
4-12-73
te = 110+ 76+ 11 110
Steam condensate ( + O+ ) x 60x8= 48,720 1
( 4 )
Water overflow = a + aint 572 + a =x60x8= 275,1601
Dump water = 16,9801
Total wastewater/8 hr = 340, 8601
Weight of spinach (8.6 + 7.8 + 8.0 + 8.4) _
blanched = ( 4 y *8= 65. 6 kkg
(Volume/8 hr)/(kkg/8 hr) = 340,860 _ 5,200 1/kkeg
65.6
4-13-73
Steam condensate = 110 x 60x 8= 52,8001
Water overflow = 588 x 60x 8 = 282,2001
Dump water = 16,9801 = 16,9801
Total wastewater/8 hr = 352,0001
Weight of spinach
blanched = 8.0x 8 = 64 kkg
= 3
(Volume/8 hr)/(kkg/8 hr) naw . 5, 500 I/kkg

-97-


blanched samples. The observed count difference indicates about a
3 percent weight loss due to hot-gas blanching of peas. The short
duration runs TLFP-5 and TLFP-15 (see Appendix L) were made
under conditions similar to the long duration runs and 14-15 percent
weight losses were recorded. The weighing of partially dewatered
peas and losses in collecting blanched peas from the conveyor belt
made these values uncertain.

The higher no. of peas sinking in each of the three different salt solu-
tions from hot-gas blanched peas indicates that rehydration was not
complete even after 9 days of storage. Peas were quality graded
within a few hr of retorting and the data clearly confirm the cannery
quality control records showing lower grading of samples containing
hot-gas blanched peas. If hot-gas blanching of peas ever becomes a
common commercial practice, it will be necessary to amend the
maturity test ranges in the USDA Standards of Cuality regulations to
more accurately reflect the storage equilibrium conditions rather than
apparent maturity immediately after retorting.

Hot-gas blanching of peas for frozen preparation would require a water
application during cooling. The peas could recover most of the 3 per-
cent dehydration loss.

OVERALL CONSIDERATIONS

The experiences with in-plant hot-gas blanching of vegetables has
demonstrated that this new system is technologically feasible for
certain vegetables (such as cut green beans, peas, and spinach). The
hot-gas blanching of larger piece size vegetables (such as corn-on-
cob and beets) is not feasible due to the long residence times necessary
for achieving requisite blanching temperature in the center of the veg-
etable. The reduction in wastewater generation during hot-gas blanch-
ing of corn-on-cob and beets is not large enough to justify the high
estimated capital costs of commercial scale blanchers. The use of
hot-gas blanching looks most promising for canned or frozen cut green
beans. Although not demonstrated as yet, the use of hot-gas blanch-
ing of vegetables (such as diced carrots) destined for preservation in

a dehydrated state appears to have considerable promise. It is likely
that hot-gas blanching will first be used on a commercial scale in
unique situations. The factors which will promote commercial use of

-60-


SECTION IX
APPENDICES

Procedure for Determination of Polynuclear Hydro-
carbons in Canned Green Beans

Short Duration Hot-Gas Blanching of Cut Green Beans

Preparation Conditions and Quality Evaluation of
Canned Samples of Hot-Gas Blanched Green Beans

Wastewater Volume and Characteristics For Make-
up Water Overflow Grab Samples From Commercial
Blancher For Cut Green Beans

Short Duration Hot-Gas Blanching of Corn-on-Cob
Wastewater Volume and Characteristics For Steam
Condensate Grab Samples From Commercial Blancher
For Frozen Corn-on-Cob

Short Duration Hot-Gas Blanching of Beets
Wastewater Volume and Characteristics For Make-
up Overflow Grab Samples From Commercial
Blancher For Beets

Short Duration Hot-Gas Blanching of Spinach

Volume and Characteristics of Wastewater Samples
Collected From Hot-Gas Blancher for Spinach (1972)

Characteristics of Wastewater From Commercial
Spinach Blancher (1972)

Short Duration Hot-Gas Blanching of Green Peas

Grab Sample Characteristics for Make-up Water
From Commercial Blancher for Green Peas

-66-

76

77

79

82

83

84

84

85

86

87

88


gloves. Peas were delivered in a flume from storage hoppers with
partial removal of water on the conveyor belt of the hot-gas blancher.

Figure 1. Hot-gas blancher installed in
a food processing plant

Dry belt conveyors were used as much as possible to accomplish the
transfer to both raw and blanched vegetables. Raw No. 4 sieve size
cut green beans were delivered to the hot-gas blancher in 363 kg

(800 lb) capacity tote boxes using fork-lift trucks. Spinach was trans-
ported to a feed conveyor in a 227 kg (500 lb) capacity wheeled cart.
Corn-on-cob and beets were carried in 13.6 kg (30 1b) capacity plas-
tic pails,

After the installation and testing of the hot-gas blancher had been

-ll-


APPENDIX O

MINERAL CONTENT OF RAW, HOT-GAS BLANCHED, AND
COMMERCIALLY BLANCHED VEGETABLES (mg/100 g wet wt)

Commodity Mineral Raw Hot-gas blanched Commercially
blanched

Green beans Ca 36, 31,28 (4.2)P 30,31, 31 (0.2)? 30, 39, 46 (8. 1)”

Mg 19, 15,22 (3.6)  18,18,14 (2.3) 22,26,20 (3.1)

Pp 18,21,20 (1.6) 18, 18,18 (0) 22, 22,19 (3. 0)
Corn P 87,95, 93 (4.2) 90,88, 93 (2.6) 87, 84, 86 (1.6)
Beets pe -- 129,112, 90 89, 104,98
(19. 5) (7.5)
Spinach Ca® -- 74, 70 (2.0) 88, 86 (1. 0)
Mg* -- 99, 99 (0) 95, 92 (1.6)

Ca 39, 48,53 (7.2) 65, 73,60 (6.5) 69, 63, 65 (3.1)
Mg 62,62,40 (12.7) 65,75,59(8.1) 56,43, 36 (10.1)
P 36, 34,29 (3.6) 35, 31,34 (3.0) 41,41, 39 (2.4)

Fe 2.3,2.2,3.2 2.5,3.0,3.7 2.5,1.9, 3.0
(0. 6) (0. 6) (0. 6)
Peas Ca  24,27,23 (2.1) 23,23,22 (0.3) 20,21, 19 (0.8)

Mg 34, 36,33 (1.0)  36,36,35 (0.5) 29, 30,28 (1.3)

P  93,92,81(6.7)  95,95,90(2.7) 82,73, 81 (5.4)

Fe 1.8,2.1 (1.0) 3.3,2.7(0.5)  2.2,1.8,1.6
(1.3)

a Canned sample
b Standard deviations shown in parentheses.

-94-


The estimate of the weight of peas blanched in the commercial blanch-
er being monitored was made from can counts, can size, fill weights
of each can size, and subtraction of the weight of peas contributed by
the hot-gas blancher during the period monitored. A check list for
recording measurements and sample collections during the operation
of the hot-gas blancher is shown as Appendix T.

The eight hr total volume wastewater discharge from the hot-gas
blancher, two hr grab samples, and a composite of equal volumes of
four consecutive two hr grab samples from the commercial blancher
wastewater were analysed for BOD, COD, SS, and pH by standard
methods, Taras?. The wastewater samples were refrigerated from
shortly after collection until laboratory analyses were started.

The wastewater samples were not screened prior to analysis and were
shaken before aliquot removal to give uniform suspension of insoluble
material. No preservatives were used to stabilize the refrigerated
wastewater samples prior to analysis.

Wastewater samples from the blanching of cut green beans, corn-on-
cob, and beets were analysed at a laboratory in Corvallis, Oregon.
Wastewater samples from the blanching of spinach and green peas
were analysed at a laboratory in Berkeley, California.

PRODUCT EVALUATION

The evaluation of the effect of hot-gas blanching on the quality of vege-
tables took place in several stages. The initial product evaluation was
made subjectively, by blancher operators and company technical
specialists who inspected freshly blanched material from short dura-
tion exploratory experiments. Experienced observers estimated the
adequacy of blanching by noting changes in color, texture and flavor of
freshly blanched material. For exploratory runs of the hot-gas blanch-
er, where the blanched material passed subjective examination, a
measurement of the extent of reduction in peroxidase was made. This
objective test of peroxidase reduction was made hourly for the long
duration (forty hr) runs.

-16-


5-12-73 were measured for vacuum, headspace, net weight, total
count, and no. of peas which sank in three different concentrations of
brine. These tests were made on 5-16-73. The results of the exam-
ination of 24 cans of peas are tabulated in Appendix P.

The evaluation of hot-gas blanched bean samples for consumer accept-
ance was an important part of this project. It was possible to arrange
for the evaluation, by food appraisal specialists at Oregon State Univer-
sity, of samples of canned, cut green beans after various periods of
accelerated storage at 38°C (100°F).

The results obtained on samples one mo after canning are tabulated in
Table 22.

Table 22. RESULTS OF ORGANOLEPTIC EVALUATION OF CANNED
GREEN BEANS ONE MONTH AFTER CANNING

Mean Score

Factor Sample A Sample B Sample C Sample D LSD#
evaluated (hot-water) (hot-water) (hot-gas) (hot-gas (0. 05)
Appearance 4.82 4.07 4.70 4.55 0. 53
Texture 4.75 5.05 4.60 5.15 0.49
Flavor 4.95 4.77 4,32 4.77 0.60
Overall

Desirability 4.85 4.80 4.35 4.80 0.52

a Least significant difference at 5 percent probability level. When the
difference in mean scores of two samples exceeds the LSD the differ-
ence in scores is significant.

The results of testing samples of canned beans stored at 38°C (100°F)
for periods of 3 and 6 mo are tabulated in Table 23.

Samples of frozen corn-on-cob prepared with hot-gas blanching and
steam blanching (commercial) were evaluated by a 50-member panel
at Oregon State University after storage for one mo. The results from
this examination are tabulated in Table 24.

-45-


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-90-


Table 5. (continued). LONG TERM HOT-GAS BLANCHING OF CORN-

ON -COB
Date Hour of Temp, Kernel
operation? °C peroxidase
reduction, %
14 102 100
15 104 97
16 104 93
9-19-72 a.m. 17 104 98
18 106 98
19 103 99
20 102 98
21 107 92
22 107 100
23 105 100
24 107 100
9-19-72 p.m. 25 110 100
26 ooo 100
27 --- 100
28 --- 100
29 see 100
30 108 100
31 106 91
32 107 100
9-20-72 a.m. 33 104 100
34 103 100
35 107 100
36 107 100
37 105 100

Total volume wastewater samples collected after 0 to 8, 8 to 16,
16 to 24, 24 to 32 and 32 to 37 hr of operation were, 26.4, 60.5,
52.9, 52.9 and 37.8 1 respectively.

The wastewater volume and characteristic of samples collected during
hot-gas blanching of corn-on-cob are tabulated in Table 6. The water

-28-


completed, samples of commercially blanched vegetables were exam-
ined and the reduction in peroxidase level measured, Dietrich, et al.8

Beets, spinach and peas for canning are blanched until almost all
peroxidase activity is destroyed. Therefore, the target peroxidase
reduction level for hot-gas blanching of beets, spinach, and peas was
95-100 percent. Complete destruction of peroxidase activity is re-
quired to retain the quality of frozen corn-on~-cob. The target perox-
idase reduction level for both kernels and cob of hot-gas blanched
corn-on-cob was 100 percent. The level of enzyme deactivation dur-
ing blanching of cut green beans is a special case and requires care-
ful control to avoid over-blanching. Cut green beans which are hot-
water blanched to a level of 40 percent peroxidase reduction or great-
er, frequently show a separation of the skin from the bean pod in the
final canned product. This condition is known as "sloughing" and
when it occurs, the appearance of the product is much less attractive
than material consisting wholely of intact bean pods. The target
peroxidase reduction level for hot-gas blanched beans was 20 to 40
percent. A large number of short duration hot-gas blanching runs
were necessary to establish consistent operating conditions yielding
canned samples showing low levels of sloughing.

The appearance, texture and color changes in commercially blanched
samples were used, along with the peroxidase reduction values, as
targets for the performance of the hot-gas blancher. The operating
conditions (loading rate, temperature, residence time, and steam
flow) were varied systematically until a set of conditions were found
which reproduced the commercial blanching effect as closely as
possible. The hot-gas blancher was then operated for approximately
one hr under the conditions found to duplicate the effect of the com-
mercial blancher to confirm that extended operation would produce
uniformly blanched material and to provide material for preparation
of samples for quality evaluation using the commercial line equipment.

The canned or frozen samples prepared for quality evaluation were
examined by routine quality control procedures used by the plant and
by a group of company management and technical persons. The pro-
cess of sample preparation and company evaluation was repeated un-
til management was satisfied that material from the hot-gas blancher

-12-


Table 29 tabulates the dollar cost per kkg (2200 1b) of vegetable blanch-
ed for hot-gas, steam, and hot-water blanching of five vegetables.
Examples of detailed calculations are tabulated in Appendices Q, R,
and S.

Table 29. ESTIMATED COST OF BLANCHING VEGETABLES
($/kkg blanched)

Blanching System
Commodity Hot-gas Steam Hot-water

Green Beans

Fixed costs 2.19 -- 1.41
Operating cost 0.75 -- 0.99
Total cost 2.94 -- 2.40

Corn-on-cob

Fixed cost 11.70 1.11 --

Operating cost 5.20 1.40 --

Total cost 16.90 2.51 --
Beets

Fixed cost 13.28 -- 1.24

Operating cost 5.90 -- 1.01

Total cost 19.18 -- 2.26
Spinach

Fixed cost 8.26 -- 1.68

Operating cost 2.30 -- 1.21

Total cost 10. 56 -- 2.89

Green Peas

Fixed cost 4.35 -- 0.88
Operating cost = 1. 83 -- 1.51
Total cost 6.18 -- 2.39

This estimate for steam and hot-water blanching was made using pub-
lished steam requirements for blanchers (Lopez! 6), cost of operation

-56-


No.

24.

25.

26.

27.

28.

29.

30.

TABLES

(continued)

Organoleptic Panel Evaluation of Frozen Corn-on-
Cob After Storage for One Month at -18 C

Taste Panel Ranking of Three Commercial and
One Hot-Gas Blanched Sample of Canned Spinach

Energy Consumption During Hot-Gas Blanching
of Vegetables

Comparison of Wastewater Volume, BOD, COD,
and SS from Hot-Gas and Commercial Blanching

of Vegetables

Percentage Reduction of Wastewater Volume, BOD,
COD, and SS Due to Hot-Gas Blanching of Vegetables

Estimated Cost of Blanching Vegetables

Basis for Estimating First Cost of Commercial
Scale Hot-Gas Blanchers

-vi-

Page

46

47

48

50

52

56

57


APPENDIX L

SHORT DURATION HOT-GAS BLANCHING OF GREEN PEAS

Run Feed Product Temp, Residence Steam Peroxidase

no. wt, kg wt, kg °C time, sec flow reduction, %
kg/min

TLFP-14> -- -- 121-166 -- 2.0 99

TLFP-15 9.8 8.3 129-138 144 1.0 99

TLFP-16 -- -- 138-143 190 1.0 --

a 10 min operation.
b 15 min operation.

APPENDIX M

GRAB SAMPLE CHARACTERISTICS FOR MAKE-UP WATER FROM
COMMERCIAL BLANCHER FOR GREEN PEAS (Volume = 570 1/hr)

Sampling Weight Sample BOD, CoD, ss, pH
date blanched, type? = mg/1 mg/l _mg/1
(operating kkg
time)
5-8-73
(0-2 hr) 4.8 2hr 5980 12200 320 7.5
(2-4 hr) 5.4 4hr 3440 5820 200 8.5
(4-6 hr) 5.0 6 hr 4300 5790 240 8.8
(6-8 hr) 5.2 8 hr 5010 7630 230 8.5
5-9-73
(0-2 hr) 5.1 2hr 6130 8550 450 8.3
(2-4 hr) 5.6 4hr 5640 9410 260 8.0
(4-6 hr) 5.4 6 hr 5250 9800 220 8.0
(6-8 hr) 5.1 8 hr 4200 8160 390 8.0

-88-


Spinach

A partial study of hot-gas blanching of spinach was made in March, 1972;
a more detailed study was made during the 1973 canning season.

The results of short duration runs with washed spinach are tabulated in
Appendix I. These runs were sufficient to prepare enough samples for
quality evaluations and to receive approval of the cannery management
to make long-duration runs and return hot-gas blanched spinach to com-
mercial production.

The conditions used for the long-term hot-gas blanching of spinach
were: a loading rate of 10.7 to 14.6 kg/m“ (2.2 to 3.0 lb/ft“), a feed
rate of 113-202 kg (248-444 lb)/hr, operating temperatures of 99-
118°C (210-245°F), a residence time of 108 sec and an average steam
flow of 0.91 kg (2.0 1b)/min. The results of the long-duration hot-gas
blanching of spinach are tabulated in Table 11.

Table 11. LONG TERM HOT-GAS BLANCHING OF WASHED SPINACH

Date Hour of Feed rate, Temp, Peroxidase
operation® kg/hr °C reduction, %

3-28-72 0 -- -- --

1 -- 110 97

2 -- 118 97

3 202 104 --

4 -- 106 99

5 -- 107 --

6 -- 110 99

7 -- 106 99

8 120 113 --
3-29-72 9 -- 110 99

10 154 104 --

ll -- 99 99

12 113 104 --

13 -- 104 99

14 154 110 --

-33-


APPENDIX P

VACUUM, HEADSPACE, NET WEIGHT, COUNT, AND MATURITY
OF CANNED GREEN PEAS

Vacuum, Headspace, Net wt, No. of 50 sinking in NaCl brines
in. of Hg in. /32 oz Count 11% 13% 15%

Commercial line samples

8 13 16.9 700 19 7 0
11 13 16.9 680 20 6 1
8 13 16.9 701 15 4 0
10 14 16.7 657 15 4 0
10 15 16.6 641 24 5 0
11 13 16.8 660 20 4 0
10 16 16.4 716 14 4 0
ll 13 16.7 648 22 6 2
10 10 17.1 681 19 5 0
il 14 16.8 676 17 5 10)
6 13 16.6 622 16 6 1
Ave.
10 13 16.8 671 17 5 0
Special hot-gas blanched
7 9 16.9 641 11 1 0
Hot-gas blanched
5 13 16.8 687 23 7 0)
5 16 16.7 710 13 8 0
6 12 16.8 667 20 5 2
5 12 16.9 684 16 8 2
6 14 16.8 667 22 8 3
5 8 17.7 688 17 4 1
5 13 16.7 706 19 5 1
5 12 17.7 689 21 10 0

-95-


blancher had two continuous liquid waste discharge lines, one for steam
condensate and one for water overflow. Single measurements of the
flow rates of these lines in 1972 gave a volume of 227 1 (60 gal. )/min
for the overflow line and 113 1 (30 gal.)/min for the steam condensate
line. The volume of these lines were measured frequently in 1973 and
the results are tabulated in Table 14.

Table 13. WASTEWATER VOLUME AND CHARACTERISTICS FOR
HOT-GAS BLANCHING OF WASHED SPINACH

Sampling Wastewaterb Weight BOD, coD, ss, pH
date volume, 1 blanched, mg/1 mg/1 mg/l
kkg
3-28-72 1.8 1.35 a 49900 3400 7.4
3-29-72 0. 74 1.18 a 13200 2600 7.7
4-12-73 0.42 1.12 28600 41300 4700 7.0
4-13-73 0. 58 1.14 15600 24100 1200 7.3
4-14-73 0.51 1.12 3700 5400 250 5.9

2 BOD determinations were not made for wastewater samples collected
in 1972,
Total volume collected during eight hr of operation,

Table 14. STEAM CONDENSATE AND MAKE-UP WATER OVERFLOW
RATES FOR COMMERCIAL SPINACH BLANCHER

Sampling dates Weight Steam Water

and times blanched, condensate overflow
kkg/hr discharge rate, discharge rate,

1/min 1/min
4-9-73 lpm 8.7 68 565
4-12-73 10am 8.6 110 604
12 pm 7.8 76 572
2pm 8.0 110 572
4 pm 8.4 110 545
4-13-73 8am 8.0 110 588

-36-