Ozone Treatments ofFresh Atlantic Cod, Gadus morhua
ELINOR M. RAVESI, JOSEPH J. L1CCIARDELLO
and LINDA D. RACICOT

Introduction
The strong oxidizing nature of ozone,
known since its discovery in 1840, hasmade it a useful agent for seawater disin­
fection (Blogoslawski et aI., 1975;
Blogoslawski, 1977) by effectively de­stroying bacteria, yeasts, and viruses. Its
potential value for shellfish depuration
was first reported by Voille (1929) andlater by Salmon and Le Gall (1936).
More recently, Blogoslawski and Stewart( 1977) cited in a review article numerous
reports of the successful use of ozone toI) control microbial populations inclosed marine systems, 2) depurate shell­fish, 3) improve water quality and pre­vent disease in aquaculture, 4) inactivate
red tide toxins, and 5) prevent biofoul­ing, i.e. the rapid and undesirable growthof aquatic flora and fauna which can plugmechanical systems.
Ozone has been reported in numerous
studies to extend the storage life of many
perishable foods by slowing decomposi­tion caused by microorganisms. Thesestudies were reviewed by Farquhar andRice (1982). Storage life extension offish using ozone was first reported by the
French investigators Salmon and Le Gall
( 1936). They found they could extend thestorage life of whiting 4 days by rinsing

ABSTRACT-The effect of ozone was in­vestigated by various applications on theiced storage life of fresh gUlled Atlantic
cod. Gadus morhua. The different treat­ments incorporated the ozone in either theice, rinse water, or chilled seawater. Shelf
life. as assessed by sensory, chemical, andmicrobiological tests. was not sufficiently
extended by any of the treatments.

49(4), 1987

the fish with freshly ozonated seawaterand then packing them in small boxes
with ozonated ice.
Interest in the use of ozone for fish
quality preservation was not then sus­
tained, but resumed about 30 years later
when Japanese investigators (Haraguchi
et aI., 1969) reported a 4-day storage life
extension by ozonation of brine-dippedjack mackerel and striped mackerel.
In a more recent study (Nelson, 1982),
tests were conducted to determine
whether the storage life of freshly caught
Alaska salmon, Oncorhynchus spp.,
could be extended by packing the fish in
ice made from ozonated water comparedwith fish conventionally packed in ice
made from nonozonated water. The bac­terial count on the fish kept in ozonatedice (94 x 103/g) was only 3 percent of thaton fish packed in regular ice (2.7 x 106/g)
after 8-9 days storage at 28°F. The resultsof this study indicated that the fresh qual­
ity of ozone-iced Pacific salmon can be
maintained up to 6 days. And, DeWitt etal. (1984) report a "possible" extensionof i-2 days in the storage life of Gulf of
Mexico shrimp with the use of ozonatedice.
The nature and rate of deterioration
varies considerably with different species(Bramsnaes, i965); therefore, the pur­pose of our study was to determine if theuse of ozone could, by various treat­ments, extend the storage life of gutted
cod as it appears to do with some otherspecies of fish.
E. M. Ravesi and J. J. Licciardello are with the
Gloucester Laboratory, Northeast Fisheries Cen­ter, National Marine Fisheries Service, NOAA,
Emerson Avenue, Gloucester, MA 01930. L. D.
Racicot is with Quaker Foods, 617 W. Main
Street, Barrington, IL 60010.

Materials and Methods
This study was conducted in two parts.
For Part I, 36 eviscerated cod (3.5-6
pounds each) i-day post mortem, were
procured from a Gloucester, Mass., dayboat in March, i984. These fish were
held in ice for 24 hours while freshozonated ice was prepared. They werethen sprayed with tap water and divided
into three treatment groups of i2 fish
each. The treatments were: i) Control
samples stored in freshwater flake ice, 2)rinsed for one minute with 500 ml offreshly prepared ozonated water, whilesuspended by their tails, then stored inflake ice, 3) stored in 2 inch cube-sized
chunks of ozonated ice.
The fish were stored in commercial
plastic fish boxes (125-pound capacity).
Each box contained six fish divided into
two layers of three fish and was covered
with a sheet of polyethylene during stor­
age. The boxes were kept at an ambient
temperature of about 37°F. Two fishfrom each group were tested after 0,5,9,
i3, 16, and 20 days of treatment (2, 7,
11, 15, 18, and 22 days post mortem).
One fillet from each fish was used forbacteriological analyses and sensory
evaluation, and the second was used for
pH and chemical tests. All tests wereconducted in duplicate.
For Part II of the study, 26 market­
sized eviscerated cod 1 day post mortem
were purchased from a local day-boat inJune 1984. Two fish were reserved for
examination and testing as 0 day refer­ence samples. The remaining fish, afterrinsing with tap water, were divided into
four groups of six, weighed and put into
each of four plastic barrels (32-gallon ca­
pacity) containing chilled seawater

37

(CSW). The fish:seawater:ice ratio inthese containers was 3: 1.5: 1. These bar­rels were evenly divided into two treat­ment groups: Group I (control) was aer­
ated with purified compressed air, andgroup 2 was ozonated with gaseousozone. The barrels were stored at 37°F
and daily, for 7 days, the appropriate gas
was bubbled for 20 minutes into thesebarrels through a 12-inch long air stone
placed at the bottom of each. Two fishfrom each group were tested after 0, 1,4,
and 7 days of treatment. After 7 days, theremaining fish were removed from thechilled seawater, stored in flake ice incovered commercial plastic fish boxes,
and testing continued during an addi­
tional 8 days storage.
The ozone used in this study was pro­
duced in a Welsbach Ozonator' (Model408) using purified oxygen as the feed
gas. The ozonated water (about 8.0 ppm)
was produced by bubbling the gaseousozone through an air stone into a streamof water flowing through an 18-foot long
I!-inch PVC pipe. To enhance saturationof the water with gas, the pipe was
packed with small stones and it contained
four V-shaped bends with *-inch restric­
tors. It was collected in a covered nal­
gene carboy containing flake ice and was
drawn from a spigot at the bottom of the
carboy. The ozonated chunk ice (about
0.6 ppm 03) was made by chopping
blocks of ice prepared by fillingpolyethylene-lined metal trays (l2X42
x2 inches) with ozonated water andfreezing these rapidly in a plate freezer.
The procedure for testing the fish in Part
II of the study was similar to that fol­
lowed in Part I.
For sensory analyses, each fish, andsubsequently its skinned fillets, was eval­uated in the raw state. Examination wasmade of the following characteristics:I) General external appearance of thefish, 2) condition of the eyes, 3) appear­
ance and odor of the gills, 4) condition of
the muscle, resistance to pressure,gaping, and adherance to the skeletalbone, 5) appearance and odor of the ab­dominal cavity, 6) color of the muscle­
discoloration and blood spots, and 7)
IMention of trade names on commercial firms
does not imply endorsement by the National
Marine Fisheries Service, NOAA.

38

odor of the muscle.
The fillets were then steamed in foil­
covered pans at 212°F for 15 minutes andevaluated by a 6-member panel of labora­
tory staff members for appearance, odor,
flavor, and texture. Samples were rated
on a scale from I (inedible) to 9 (excel­
lent). When the average score of any of
the above attributes decreased to a valueof 5.5 (between fair and borderline) the
end of the storage life was consideredreached.
To obtain pH, a 20 g sample of fishmuscle was blended with 40 ml of dis­tilled water for I minute and the pH of thehomogenate was measured with a Fisher
Model 320 expanded scale pH meter.
Dimethylamine (DMA) and trimethy­
lamine (TMA) analyses were performed
by gas chromatography using N­
propylamine as the internal standard(Lundstrom and Racicot, 1983). Results
are expressed as MgN/IOO g muscle.
Thiobarbituric acid (TBA) reactive
substances were determined by themethod of Yu and Sinnhuber (1957),
modified by the addition of disodium
ethylenediamine tetracetate (EDTA) andpropyl gallate to prevent oxidation during
blending. TBA number was calculatedby the procedure reported by Sinnhuber
and Yu (1958).
The concentration of ozone (03) inwater and ice was determined by an iodo­
metric method (APHA, 1971). Measured
volumes of water and weighed amountsof ice were transferred to 8-ounce jars
containing the necessary volume ofpotassium iodide solution, and the jars
were immediately capped. When ice wastested, the jar were set in pans of tepid
water to hasten melting. The ozone con­centration was measured immediately
after melting was complete. Ozonatedchunk ice was used in this study because
we were unable to measure residualozone in flake ice which had been pre­pared from water with an ozone concen­
tration as high as 8.0 ppm. The presenceof ozone in the chunk ice was short lived
and was not measurable after 24 hours.
About 50 percent of the originally meas­
ured ozone disappeared after one hour.
The aerobic plate count (APC) was
made from appropriate dilutions onto
pour plates of TPE agar (Standard Meth­
ods Agar reinforced with 0.5 percent

Bacto-peptone and 0.5 percent NaC I) as
recommended by Lee and Pfeifer (1974)
for seafoods. Duplicate plates were incu­
bated at 68°F and colony counts weremade after 5 days.

Results and Discussion
The use of ozone in rinse water and/orin ice are procedures which could be usedby fishermen aboard vessels or by pro­
cessors in their plants. The application ofozone to chilled seawater might enablefishermen to sustain high quality in theircatches when trips of several days arenecessary. It is understandable that if
ozonation is to benefit the storage life offish, the sooner it is applied, the greater
will be its advantage. However, its possi­
ble benefit to fish of several days post
mortem age carmot be discounted as Castell(1953) showed that percentage bacterial re­duction on fillets as a result of washinground fish by various means was low forrecently caught iced fish and relatively highfor fish which had been in ice for several
days. Circumstances prevented us fromstudying fish immediately after their re­moval from water. Prior to treatment andstorage, all fish were examined and judged
by raw sensory evaluation to be in excel­
lent condition. For the duration of Part Iof the study, no perceptible sensory dif­ference among any of the treatments wasnoted in the raw whole fish or fillets.
The sensory panel scores (Table I) of
cooked cod treated with ozone in various
ways and stored in ice for Part I of thisstudy are shown. There was no signifi­
cant difference in any of the attributes
due to treatments at any time other than at
the 9th day if treatment when the controls
were significantly lower (I percent level)in flavor score from the other two treat­ments. This difference was not main­tained so that neither the ozone-rinse nor
the ozone-ice appears to extend the pan­els acceptance of the iced cod. The re­sults of chemical, pH, and bacteriologi­
cal analyses for Part I of this study aresummarized in Table 2.
There was a large deviation in values
obtained from fillets of the same treat­ment for all three amines throughout the
study. All treatments showed an increasein TMA content (Fig. I) after 5 days.
After 13 days, the ozone-rinsed fish had
a slightly higher content of TMA than the

Marine Fisheries Review

noted, however, that the "ordinary" icewhich they used was known to be far
from sterile, having a presence of about
25,000 organisms/cc, among which
Pseudomonas fluorescens were domi­
nant. Fish stored on this nonsterile ice
was judged inedible at the 12th day ofstorage, while those on the sterilized ice
were not considered objectionable until
the 16th day.
Rancidity did not develop in any of the
fish regardless of treatment. All showed avery gradual and very small increase in
TBA number throughout the 20 day stor-

control, while a little less TMA wasfound in the ozone-iced fish, but differ­ences were not significant.
The DMA content of the cod fillets
was low throughout the study (less than
3.9 mgNIlOO g for all treatments, but as
can be seen from Figure 2, the treatments
had no effect on DMA content. Salmon
and Le Gall (1936), using either cod or
whiting (not stated), did find a lower con­centration of TMA and total volatile ni­
trogen throughout a 12-day storage pe­
riod in fish stored in ozonated ice
compared with ordinary ice. It must be

age period. Nelson (1982) reported alower malonaldehyde concentration in
fresh Alaskan salmon (pink, coho, sock­eye, and silver) stored in ozonated ice
compared with regular ice. However, un­like with salmon, rancidity is not a prob­
lem with conventionally iced cod and ourconcern was in whether ozone would
cause it to develop. Our results indicatethat the very brief contact of the ozone
with the fish did not result in oxidation of
unsaturated lipid material. It is highly un­
likely that the ozone ever contacted fatty
acids.

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12

14

16

18

DAYS IN ICE

20DAYS IN ICE

Figure I.-Trimethylamine content of gutted cod treatedwith ozone in various manners and stored in ice.

Table 1.-SenllOry scores (:!:SD) lor appearance, odor,
flavor, and texture of cooked cod treated with ordinary Ice(Control), or ozonated water (Rlnsed),. or ozonated Ice(Iced).

Figure 2.-Dimethylamine content of gutted cod treatedwith ozone in various manners and stored in ice.

Table 2.-Chemlcal and bac1erlologlcal analyses and pH values of cod trea1ed
Ice (Control), an ozonated rinse, (Rinsed), and ozonated Ice (Iced).

with ordinaryDays
storage

Treatment(mgN/100g)

TMA(mgN/100g)

DMA(mgN/100g)

TMAO(mgN/100g)

TBA no.
(20·C)

7.8:t1.3
8.0:t1.1

0

Control
Rinsed

0.18:t0.08
0.12:t0.02

0.10:t0.06
0.25:t0.12

83.6:t0.4
85.7:t2.4

0.50:t0.13
0.60:t0.06

9.4(:t3)X1()3
7.7(:t8.1)x 103

6.6:t0.4
5.8:t0.0

7.6:t0.9
7.8:t0.6
7.8:t0.7

7.7:t0.9
7.7:t0.9
7.7:t0.9

5Control
RinsedIced

1.19:t0.53
1.03:t0.73
0.67:t0.5O

1.20:t0.29
0.86:t0.17
1.42:t0.95

76.2:t1.1
75.2:t2.4
78.8:t6.0

0.54:t0.0
0.61:t0.09
0.62:t0.05

187.3(:t134.0)X103
72.3(:t17.1)X103
142.1(:t161.1)X103

6.7:t0.0
6.8:t0.1
6.6:t0.1

6.3:t0.9
7.1:t0.6
7.2:t0.8

6.2:t0.9
6.8:t0.9
7.2:t0.7

9Control
RinsedIced

10.36:t6.68
5.52:t5.13
5.45:t0.77

2.01:t1.28
0.93:t0.28
2.59:t1.80

59.7:t4.7
71.8:t13.4
66.9:t16.2

0.67:t0.01
0.69:t0.08
0.73:t0.0

14.7(:t1.6)X106
9.4(:t5.9)X106
1.4(:t0.2)X106

7.0:t0.0
6.8:t0.0
6.8:t0.0

5.7:t1.4
5.9:t 1.7
5.9:t1.8

5.4:t1.4 6.3:t1.6
5.5:t 1.5 5.83:t1.0
5.7:t1.2 5.4:t 1.4

5.8:t 1.4
6.0:t1.0
5.6:t1.2

13

Control
RinsedIced

22.8:tl0.70
22.88:t0.27
16.28:tl0.73

2.29:t0.44
2.64:t0.35
3.04:t0.13

39.9:t28.2
35.8:t11.4
51.7:t3.0

0.59:t0.06
0.54:t0.03
0.60:t0.01

94.5(:t7.8)x 106
37.5(:t5.0)x 106
43.5(:t0.7) X106

7.0:t0.1
7.0:t0.2
7.0:t0.1

Control
RinsedIced

5.4:t 1.0
5.9:t0.7
6.3:t1.0

4.3:t2.2
4.2:t1.9
4.2:t2.2

4.1:t2.0
4.4:t2.1
4.3:t2.1

4.5:t2.4
4.6:t2.2
4.6:t2.2

16

Control
RinsedIced

31.79:tl0.91
33.07:t5.9
32.13:t0.8

2.58:t0.69
2.05:t0.57
1.72:t0.08

36.1:t5.7
38.0:t15.3
43.9:t3.4

0.65:t0.08
0.76:t0.06
0.72:t0.05

146.5(:t132.2)x 106
80.5(:t13.4)X106
179.5(:t88.4)x 106

7.1:t0.3
6.8:t0.1
7.0:t0.0

Control
RinsedIced

5.1 :t1.4
4.3:t2.2
4.0:t2.2

2.6:t1.6
18:t0.9
1.5:t0.8

3.5:t2.3
1.3:t1.5
1.7:t1.0

3.9:t2.2
3.1:t2.0
2.7:t2.2

20

Control
RinsedIced

39.40:t 11.94
41.27:t1.58
33.33:t22.37

2.07:t0.13
2.44:t1.32
1.33:t0.74

19.7:t20.9
13.9:t8.5
33.2:t21.0

0.97:t0.04
0.81:t0.08
0.84:t0.05

556(:t601)X106
106(:t36.8)X106
332(:t166)X106

7.2:t0.2
7.3:t0.2
7.4:t0.3

Days
storage

Treatment

Appearance

Odor

FlavorTexture0

Control
Rinsed

8.4:t0.8
8.4:t0.8

8.3:t0.8
8.5:t0.8

8.5:t0.8
8.5:t0.8

5Control
RinsedIced

7.7:t0.8
7.8:t0.7
8.0:t0.9

7.8:t0.8
7.6:t1.0
7.8:t0.99Control
RinsedIced

6.3:t 1.1
7.4:t0.5
7.1:t0.7

6.3:t1.2
7.3:t0.5
7.0:t0.7

13

Control
Rinsed
Iced

16

20

49(4), 1987

APC
(20·C)pH

39

A gradual increase in pH resulted in
the iced controls and both of the ozone
treated fish. The ·rate of increase did notvary with the treatment, just as would be
expected from the amine production.
Figure 3 shows the results of aerobic
plate count. None of the treatments ap­
pear to delay an increase in bacterial
counts. Salmon and Le Gall (1936) re­
ported a marked decrease in the numberof microorganisms observed on the fleshof whiting immediately following anozonated seawater wash. This difference
was not apparent between the ozone­
rinsed and control fish in our study; how­
10'

Ie!
::;;

~

Id

'-'
ll:
W

"­
...
Q'

I

"'

I­

'ell<ilo'O~-""4!--""8!:---:!I2!:---!I6!:---:!20
DAYS IN ICE

Figure 3.-Aerobic plate countof gutted cod treated with ozone
in various manners and stored inice.

ever, the initial aerobic plate counts inour study were low for all of the fish.
Unfortunately, Salmon and Le Gall
(1936) did not report bacterial counts
after storage. In the study with Alaska
fresh salmon, Nelson (1982) reported
that when the ozone contacted the skin of
the fish, the bacterial counts remained in
the tens and hundreds of thousands after
8-9 days of storage on ozonated ice while
the controls showed counts in the
million-plus range. De Witt et al. (1984),
in two separate studies with Gulf of Mex­
ico shrimp, reported that storage inozonated ice had no effect on the bacte­rial spoilage of shrimp in one study, but
could possibly have a 1-2 day storage life
extension effect on their bacteriologicalspoilage in the second study.
Sensory evaluation scores for cod heldfor 7 days in either aerated (controls) orozonated chilled seawater prior to storage
on ordinary ice for Part II of this study aresummarized in Table 3. Prior to day 7,
there was no significant difference in anyof the attributes between the different
treatments. At days 7 and II, the flavor
and odor of the ozonated fish were rated
significantly lower than the flavor andodor of the control samples. Beyond the11th day of treatment, there was no sig­
nificant difference between treatments.
Examination of the raw whole fish andfillets did not reveal any differences be­
tween the treatments for off-odor devel­
opment. At day 4, both of the ozonatedsamples felt less firm and resilient than

Table 3.-sensory scores (±SD) for appearance, odor,
flavor, and texture of cooked cod treated prior with aerated
CSW plus Ice (Control) and ozonated CSW plus Ice(Ozonated).

the control fish; however, this observa­
tion did not seem to influence taste panel
results. This softness was still noted in
the ozonated samples at 7 and II days,
but it is not clear from taste test results if
this influenced panelists' texture scores.
At 7 and II days, the skin of ozonated
cod seemed more faded or bleached thanthe controls, but observations on the ini­tial color of individual fish were notmade and recorded, so this difference
may not be actual. Beyond 11 days, there
was no obvious differences in the generalcondition of the whole fish or fillets.
Table 4 summarizes the results ofchemical, pH, and bacteriological analy­
ses for Part II of this study. All of these
data, with the exception of pH, would
seem to indicate that not only did ozona­tion, as performed by us, have no storage
life extension effect on cod, but rather it
may have accelerated deteriorative proc­
esses.
Figures 4 and 5 show amine for­mations. As with the treatments in Part Iof this study, the rate of TMA formation
was more rapid in the ozonated than in
the control fish. It is difficult to explain
why ozonated samples had a higher TMA
content than controls, since reducing
agents usually break down TMAO to
TMA. It may be possible that theozonation treatment was selecting out
bacterial species that were capable ofproducing TMA from TMAO. Unfortu­
nately, there was no sampling done be­
tween day 1 and day 4, so it is not known

Table 4.-Chemical and bacteriological analyses and pH values (±SD) of cod treated with eereted CSW plus
Ice (Control) and ozonated CSW plus Ice (Ozonated).
Days
storage0Treatment(mgN/l00g)

TMA(mgN/l00g)

DMA(mgN/l00g)

TMAO(mgN/l00g)

TBA no.
(20°C)

Control

0.35±0.33

0.09±0.06

71.8±7.2

0.65±0.05

7.3(±6.0)x 1()3

6.7±0.3

ControlOzonated

0.12±0.06
0.30±0.14

0.41 ±0.52
0.18±0.06

70.5±21.1
64.8±1.6

0.71 ±0.06
0.88±0.01

9.2(±3.7)Xl03
1.7(±0.4)x 103

6.8±0.3
6.7±0.2

APC(20°C)

pH

Days
storage

Treatment

Appearance

Odor

FlavorTexture0

Control8.7±0.7

8.6±0.7

8.1±0.8

8.1 ±1.1

ControlOzonated

8.8±0.5
8.8±0.5

8.8±0.4
8.7±0.5

8.8±0.4
8.7±0.57.8±1.4
8.3±0.8

4

ControlOzonated

0.29±0.11
0.25±0.10

0.46±0.15
0.56±0.41

70.2±4.2
66.4±4.2

0.72±0.05
0.60±0.08

6.5( ± 1.6) x 103
16.0(±4.2)Xl03

7.0±0.4
6.8±0.2

4

ControlOzonated

7.8±0.5
7.4±0.8

7.7±0.7
7.7±0.7

7.5±0.7
7.4±0.77.3±1.0
6.9±1.2

7

ControlOzonated

2.88±2.23
15.52±2.76

0.77±0.19
1.10±0.33

51.3±16.7
38.2±4.2

0.69±0.06
0.74±0.01

118.5(±140.7)x 103
606.0(± 199.4) x 103

6.6±0.0
7.0±0.3

7

ControlOzonated

7.8±0.5
6.6±0.7

7.4±0.7
6.2±1.0

7.3±0.7
6.2±1.2

7.3±0.7
6.4±0.5

11

ControlOzonated

16.20±6.4735.03±5.71

1.11 ±0.54
1.40±0.12

32.8±7.4
4.2±4.1

0.85±0.06
1.05±0.05

2.0( ± 1.7) x 106
5.3(±3.1)Xl06

6.9±0.4
6.7±0.2

11

ControlOzonated

6.0±1.6
6.3±0.9

6.1 ±1.2
4.7±1.2

6.3±1.2
4.9±1.0

5.3±1.7
5.8±0.9

11

ControlOzonated

16.20±6.4735.03±5.71

1.11±0.54
1.40±0.12

32.8±7.4
4.2±4.1

0.85±0.06
1.05±0.05

2.0(±1.7)Xl06
5.3(±3.1)Xl06

6.94±0.5
6.74±0.2

13

ControlOzonated

6.1±0.7
6.3±0.6

5.4±1.0
4.2±1.55.3±1.0
4.4±1.6

4.8±1.6
5.5±1.7

13

ControlOzonated

10.25±7.9242.68±1.92

1.63±0.47
2.75±1.7943.8±17.0
2.4±0.4

0.75±0.0
0.89±0.0

8.4(1.5)Xl06
22.25(±20.9)x 106

7.2±0.0
7.1±0.2

15

ControlOzonated

5.6±1.3
5.8±0.9

3.7±2.2
4.4± 1.4

3.8±2.5
4.7±1.3

4.0±2.3
5.3±1.2

15

ControlOzonated

33.44±1.2437.42±9.81

1.73±0.14
1.02±0.26

12.0±7.8
0.8±0.3

0.62±0.13
0.80±0.13

22.1(±4.7)Xl06
43.0(±25.5)Xl06

7.1±0.1
6.9±0.040

Marine Fisheries Review

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DAYS STORAGE

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2

3

4

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6
7
8
9
DAYS STORAGE

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12

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15

Figure 5.-Dimethylamine content of gutted cod held 7days in aerated (control) or ozonated chilled seawater, andthen stored in ice.

Figure 4.-Trimethylamine content of gutted cod held 7days in aerated (control) or ozonated chilled seawater andthen stored in ice.

if TMA fonnation began earlier in theozonated fish.
Figure 6 shows supporting evidencewith higher bacterial levels in theozonated fish. At the beginning of thisstudy, the bacterial level of ozonated
CSW was 260,000 compared with
333,000 in the aerated CSW. The verysmall reduction in the original bacteria
count may have been the cause of theunexpected results in Part II of this study.
However, when the ozone conoentrationof the ozonated CSWwas analyzed andfound to be about 5 ppm, we assumed thetreatment to be sufficient. Daily detenni­
nation of the ozone concentration in the
CSW immediately following ozonation
was attempted, but the bloody, discol­ored nature of the water made ozone
measurement uncertain. On day 7, when
the remaining fish were removed fromthe CSW for storage on ordinary ice, theaverage bacterial count of the water fromthe ozonated tanks was 34 x J06 ml.
We are unaware of any reported
studies of ozonated sea water as a preser­
vation technique; however, Haraguchi etal. (1969) investigated the preservationof jack mackerel, Trachurus trachurus,
and striped mackerel, Caranx mertensi,
using ozone in a 3 percent NaCI solution.
Although they reported an ozone concen­
tration of only 0.6 ppm, it might be that
their contact time between the fish andthe ozone exceeded ours, since they49(4), 1987

Figure 6.-Aerobic plate countof gutted cod held 7 days inaerated (control) or ozonatedchilled seawater, and then storedin ice.

o

4

6

B

10

12

14

DAYS STORAGE

ozonated their brine solutions 30-50 min­utes before the fish were added and an
additional 30-60 minutes after the fish
were added. The reported stability ofozone in their brine solution, however, ispuzzling. The ozone may have been re­acting with one of the components of theseawater to produce a bactericidal ion orcompound.
They found initially, that the viablecount of bacteria on the surface of the fish
dropped to I x 10- 2 to 1 X 10- 3 of thecontrol due to ozone treatment and wasdelayed about 4 days while decreases insensory values (raw) were delayed byover one week, lengthening the storage
life of the fish 1.2-1.6 times. Their re­sults show, however, that the ozone
treatment had little effect on the bac­terial count on the muscle of the stripedmackerel.
The major disadvantage due to theozone treatment found by the Japanese
investigators was the loss of the fresh­fish smell and the acquisition of a "dried­
fish odor" which they attributed to theoxidation of the fish oil by ozone. This
would be contrary to results of the Alaska
salmon study (Nelson, 1982) where thelevel of rancidity in the control samples
was more than 3 times greater than in theozone treated samples.
In Part II of our study, as in Part I,
rancidity was never detected by taste pan­elists and TBA numbers remained low(l.0) throughout the storage period.
Treatment had no effect on pH changes
and those values reported here are nonnal
for iced cod.
The failure of ozone by various tech­41

niques to prolong the shelf life of gutted
cod is similar to the result of a study con­ducted by Vyncke (1981) which showed
no extension in the shelf life of cod fillets
by an ozonated water dip.

Acknowledgment
The authors wish to thank Robert Van
Twuyver for helpful technical assistance.

Literature Cited
APHA. 1971. Ozone (residual). In M. J. Tareset al. (editors), Standard methods for the ex­amination of water and waste water, 13th ed.,p. 271. Am. Public Health Assoc., Wash.,
D.C.
Blogoslawski, W. J. 1977. Ozone as a disinfec­
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C.N.E.X.O., 4:371.
_ _ _ _ , C. Brown, E. W. Rhodes, and
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Symp. Ozone Water Wastewater Treatment.

42Int. Ozone Inst., Syracuse, N.Y.
_-,--=-_and M. E. Stewart, M. E. Browning.
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Syracuse, N.Y.
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Castell, C. H. 1953. Reduction of bacteria con­tamination on fillets by washing the round fish
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Lee, J. S., and D. K. Pfeifer, 1974. Influencesof recovery media and incubation tempera­

tures on the types of microorganisms isolated
from seafoods. J. Milk and Food tech. 37:553.
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chromatography determination of dimethy­
lamine and trimethylamine in seafoods. J.
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the durability of conservation of fish. Rev.
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Sinnhuber, R. 0., and T. C. Yu. 1958. 2­
Thiobarbituric acid method for the measure­ment of rancidity in fishery products. 2. The
quantitative determination of malonaldehyde.
Food Technol. 12(1):9.
Voille, H. 1929. On the sterilization of seawaterby ozone. Application of this method to purifi­
cation of contaminated shellfish. Rev. d'Hyg.
Prevent. Med. prevent. [Jan.]Yu, T. C., and R. O. Sinnhuber, 1957. 2­
Thiobarbituric acid method for the measure­ment of rancidity in fishery products. Food
Technol. 11(2):104.
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11th Meet. of West-European Fish Technol.
Assoc., Copenhagen, August 1981.

Marine Fisheries Review