In-line dewaxing of edible vegetable oils

A method for the combined in-line bleaching and dewaxing of vegetable oils which includes the steps of bleaching the vegetable oil with a sufficient amount of bleaching clay and filter aid at a temperature of about 80.degree.-130.degree. C. for about 15-60 minutes, followed by rapid cooling of the bleached vegetable oil containing the bleaching clay, to a temperature of about 0.degree.-15.degree. C. for about 15 minutes-4 hours to thereby dewax the vegetable oil. The spent bleaching clay, waxy material and other impurities in the vegetable oil are then seaparted at low temperatures of about 0.degree.-20.degree. C., by such means as filtration, to thereby recover the bleached and dewaxed vegetable oil.

BACKGROUND OF THE INVENTION 
This invention relates to an in-line combined bleaching and dewaxing 
process for treating edible vegetable oils to produce a vegetable oil that 
has acceptable storage characteristics. 
Crude vegetable oils are extracted from plant tissue and include such 
varieties as corn, milo, rapeseed (canola), ricebran, sunflower and 
safflower. 
Crude vegetable oils contain undesirable minor components or impurities 
such as pigments, free fatty acids, phospholipids and oxidation products, 
which can cause undesirable color and/or "off flavors" in the finished 
vegetable oil. In addition, certain higher melting components must be 
removed from the vegetable oils if they are to be used in food products 
such as salad oils and dressings which must be refrigerated. Unless 
removed, the higher melting constituents would crystallize and separate 
when the vegetable oils are stored at refrigeration temperatures. 
The conversion of crude vegetable oils into an acceptable product may 
require several treatment steps including degumming, alkali refining, 
bleaching, winterization, dewaxing and deodorization. 
The term "winterization" is applied to a process for removing high melting 
material from oils whereby the oils are carefully cooled to low 
temperatures for extended periods of time to permit precipitation of solid 
material. Solid material can then be removed by filtration or other 
separation procedures. Examples of winterization processes are disclosed 
in U.S. Pat. Nos. 2,200,982 to Dedlow, 3,048,491 to Gooding and 4,035,402 
to Levine. 
Alkali refining of a vegetable oil involves its treatment with an alkali, 
such as sodium hydroxide, to remove free fatty acids, phospholipids, trace 
metals, pigments and oxidation products. The alkali solution neutralizes 
the free fatty acids contained in the crude vegetable oil, producing a 
soap stock which can be continuously removed by centrifugation. 
Phospholipids, also referred to as phosphatides, are soluble in the 
anhydrous vegetable oil, but after treatment with an alkali solution 
precipitate out with the soap stock and can also be removed. 
Other alkali solutions, such as sodium bicarbonate, calcium hydroxide, 
potassium hydroxide, magnesium hydroxide, ammonia, and some organic bases 
can also be used in alkali refining a crude vegetable oil. Examples of 
alkali refining treatments are disclosesd in U.S. Pat. No. 3,943,155 to 
Young. 
An alternative to "chemical" alkali refining, is physical refining whereby 
oil impurities are removed by physical means in the degumming, bleaching, 
dewaxing and steam refining/deodorization steps. During degumming, crude 
vegetable oil is mixed with a small amount of water (1-3%), agitated to 
achieve hydration of gums, primarily phospholipiods, thus making them 
insoluble in the vegetable oil, and further the hydrated gums are 
separated from the oil by such means as centrifugation. When the degumming 
is done at ambient or lower temperatures, a partial removal of waxes can 
also be achieved. 
Alkali refining and degumming are alternative approaches that are generally 
used as preliminary steps in the purification of crude vegetable oils. 
Either alkali refining or degumming is generally used in combination with 
subsequent bleaching, dewaxing and deodorization treatments of the 
vegetable oil. 
The purpose of bleaching step is to further purify the vetgetable oil by 
removing residual phospholipids, trace metal complexes and pigments such 
as carotene, chlorophyll and related compounds, as well as oxidation 
products. Moreover, where the bleaching step is preceded by alkali 
refining, the bleaching treatment can also remove residual soaps left by 
the alkali refining treatment. 
In a conventional bleaching process, the vegetable oil is mixed with a 
bleaching clay which serves as an adsorbent. The bleaching clay-vegetable 
oil mixture is then heated for a period of time, and filtered to separate 
the spent adsorbent from the decolorized oil. Ordinarily, much of the 
bleaching action occurs during the holding of the oil/clay mixture at 
elevated temperatures under vacuum with intense agitation. 
In the situation where degumming is used prior to the bleaching step, the 
bleaching is generally conducted in the presence of phosphoric acid which 
reacts with residual phospholipids, as well as with the metals present in 
the vegetable oil converting the metals into phosphates. 
Activated carbon can also be used in place of the bleaching clay as an an 
adsorbent, however, for economic reasons, if it is used at all, it is 
generally mixed with the bleaching clay. 
The bleaching step can be conducted under atmospheric pressure, however, it 
is usually done under vacuum conditions to avoid oxidizing the bleached 
oil. Examples of bleaching treatments are disclosed in U.S. Pat. Nos. 
3,673,228 to Harris, 3,943,155 to Young and 3,955,004 to Strauss et al. 
The bleached vegetable oil still contains small amounts of high melting 
point components, such as saturated glycerides, wax esters, sterol esters 
and hydrocarbons which can crystallize and precipitate at ambient 
temperatures, and especially at refrigeration temperatures. It is these 
high melting point compounds, generally referred to as waxes, which are 
responsible for the haze and cloudiness of an oil. 
The conventional dewaxing process includes slow chilling of the oil to 
temperatures sufficient to crystallize the waxy components from the crude 
oil, preferably under gentle agitation. The crystallized components are 
then generally removed by a cold filtration step. U.S. Pat. Nos. 3,943,115 
to Young, 3,994,943 to Gibble and 4,035,402 to Levine disclose various 
processes for dewaxing vegetable oils. U.S. Pat. No. 2,625,482 to Mattil 
discloses a dewaxing process for lard. 
Following the bleaching and dewaxing steps, the oil may be deodorized, 
usually with steam under vacuum at a high temperature. Steam deodorization 
involves the contacting of steam with free fatty acids and other volatile 
odorous and off-flavor materials often present in the vegetable oil which 
are responsible for the undesirable odor and taste of non-deodorized oil. 
U.S. Pat. No. 3,506,969 to Baker et al discloses a typical steam 
deodorization process. 
SUMMARY OF THE INVENTION 
The present invention comprises a combined in-line bleaching and dewaxing 
process for vegetable oils which eliminates the filtration step that 
generally follows a bleaching operation, wherein spent bleach clay cake is 
removed. In essence, the present invention provides a process for refining 
crude vegetable oils by first degumming the oil, or alternatively 
subjecting it to an alkali refining treatment, then bleaching, cooling and 
holding the oil at a low temperature under agitation, followed by cold 
separation of the spent bleach clay cake, impurities and high melting 
point components. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the present invention, a crude vegetable oil is 
initially subjected to cold degumming, or alternatively, an alkali 
refining treatment. The vegetable oil is then bleached in the presence of 
a bleaching clay and filter aid under vacuum and agitation, followed by 
cooling to a low temperature under agitation and maintaining the oil at 
the cooling temperature for a time sufficient to crystallize waxy 
impurities. The bleaching clay, which is retained throughout the process 
until final separation, serves as an adsorbent for oil impurities during 
the bleaching step, and as a seeding agent to induce crystallization of 
waxes during the dewaxing step. The spent bleach clay cake and 
crystallized impurities are then separated from the vegetable oil by cold 
filtration. The bleached and dewaxed vegetable oil can also be steam 
refined and deodorized in a conventional manner. 
The present invention is applicable to a variety of vegetable oils 
including corn, milo, rapeseed (canola), ricebran, sunflower and 
safflower. 
Although alkali refining of the crude vegetable oil can be performed as a 
preliminary purification step, the alternative cold degumming treatment is 
preferred because the cold degumming treatment advantageously removes a 
portion of the waxes. The degumming treatment involves cooling the crude 
vegetable oil to temperatures, of about 0.degree. to 20.degree. C., 
preferably 10.degree. C., and mixing with a sufficient amount of cold 
water under agitation to achieve proper hydration of gums present in the 
vegetable oil and render them insoluble. For corn oil, it has been found 
that about 3% cold water by weight, agitated at about 10.degree. C. for 30 
minutes is sufficient to achieve proper hydration of the gums and render 
the gums insoluble in the oil. The oil can then be separated from the 
solids by centrifugation, followed by drying to reduce its moisture level 
to a suitable value, preferably less than about 0.1%. 
Bleaching of the degummed vegetable oil is generally carried out at 
temperatures of 80.degree. to 130.degree. C., preferably 100.degree. to 
110.degree. C. for about 15 to 60 minutes, preferably about 30 minutes, 
under vacuum and agitation. 
The amount of bleaching clay will vary depending upon the particular 
vegetable oil being bleached, generally from about 0.5 to 5% by weight of 
the vegetable oil. A wide variety of bleaching clays are available, for 
example, Filtrol.TM. (Filtrol-Harshaw Chemicals, Inc.) and Vega Plus.TM. 
(Filtrol-Canada, Inc.). 
A filter aid is also used in the bleaching step to assist the subsequent 
filtration of impurities following the dewaxing step. The amount of filter 
aid to bleaching clay can vary from about 5 to 50 parts by weight per 100 
parts by weight of bleaching clay, preferably 1 part of filter aid to 3 
parts of bleaching clay. Suitable filter aids include Hyflo Super Cel.TM. 
(Johns Manville, Inc.), Filter Cel.TM. (Johns Manville, Inc.) and 
Celatom.TM. (Eagle Picher, Inc.). 
The bleaching step is also conducted in the presence of phosphoric acid to 
remove residual phospholipids, where the crude vegetable oil has been cold 
degummed prior to bleaching. The phosphoric acid can be of varying 
concentration, preferably about 75 to 85%, and generally can vary in 
amount of from about 0.04 to about 0.12% by weight of the crude vegetable 
oil. 
Following the bleaching step, the bleached vegetable oil-bleaching clay 
mixture is then cooled to a temperature of about 0.degree. to 15.degree. 
C., preferably about 5.degree. to 10.degree. C. and maintained at this 
temperature for about 15 minutes to 4 hours accompanied by sufficient 
agitation. 
After the vegetable oil is cooled for a sufficient time under agitation, it 
is then separated from the spent bleaching clay, usually by filtration at 
low temperature. Cold filtration can be conducted at temperatures of about 
0.degree. to 20.degree. C., preferably about 10.degree. to 15.degree. C. 
The temperature maintained during the filtration step is generally the same 
as that maintained during the dewaxing step. However, during filtration 
the temperature may increase by 1-5 degrees C. above the dewaxing 
temperature due to warm-up in the processing equipment. 
The examples which follow demonstrate the efficacy of the present 
invention. The vegetable oils produced in the following examples were 
evaluated for wax removal on the basis of visual inspection of the samples 
under different temperature storage conditions of room temperature, 
referigeration, and ice-water bath. In addition, instrumental turbidity 
measurements were made using a Hach Ratio Turbidimeter. All parts and 
percentages are by weight, based on the vegetable oil, unless otherwise 
noted.

EXAMPLE 1 
Seven 1500 gram samples of degummed and dried corn oil, containing 20 ppm 
phosphorus were pretreated with 0.083% H.sub.3 PO.sub.4 at 45.degree. C., 
50 mm Hg absolute pressure for 10 minutes and then bleached with 2.5% 
Filtrol 105 bleaching clay and 0.5% Hyflo Super Cel filtering aid at 
105.degree. C. and 50 mm Hg absolute pressure for 20 minutes. The mixtures 
were rapidly cooled at an average temperature gradient of 15.degree. C. 
per minute to temperatures of 5.degree. C., and 15.degree. C. The cold 
slurry which formed was filtered on an open jacketed porcelain laboratory 
vacuum filter through two sheets of 12.5 cm diameter Whatman 41 filter 
paper. During filtration, cold brine was circulated through the jacketed 
filter. The filtered oil was dried at 45.degree. C., 0.1 mm Hg absolute 
pressure for 10 minutes to remove any moisture resulting from condensation 
and then filtered again through 2 micron Millipore tilter pads. Each 
sample was then visually evaluated during cold tests at 0.degree. C. at 
intervals of 24, 72 and 120 hours. Clarity after 24 hours was a minimum 
requirement to pass the cold test. Refrigeration tests were also conducted 
at 7.degree. C. at intervals of 1, 3 and 5 days. For the refrigeration 
test, clarity at 3 days was a minimum requirement. The samples were also 
instrumentally evaluated for turbidity using a Hach Ratio Turbidimeter. A 
maximum turbidity increase of 0.30 NTU at 24 hours was necessary to pass 
the turbidity evaluation. The results of these tests are tabulated in 
Table 1 which follows. 
TABLE 1 
__________________________________________________________________________ 
Effect of In-Line Dewaxing Parameters 
on Clarity of Bleached Corn Oil 
Holding Turbidity 
Time Refrigeration 
Increase 
Dewaxing at Dewax. 
Cold Test Test .DELTA.NTU at 0.degree. C. 
Temp. Temp. Hours at 0.degree. C. 
Days at 7.degree. C. 
24 96 
Sample # 
.degree.C. 
Hrs. 24 72 120 1 3 5 Hrs. 
Hrs. 
__________________________________________________________________________ 
1 15 0 Cloudy 
Cloudy 
Cloudy 
Hazy 
Cloudy 
Gel 0.95 
0.85 
2 15 2 Clear 
Cloudy 
Cloudy 
Clear 
Clear 
Cloudy 
0.16 
0.93 
3 10 1 Clear 
Hazy 
Cloudy 
Clear 
Clear 
Gel 0.16 
0.33 
4 10 1 Clear 
Hazy 
Cloudy 
Clear 
Clear 
Crystals 
0.14 
0.25 
5 5 0 Clear 
Hazy 
Cloudy 
Sl. Cloudy 
Cloudy 
0.20 
0.51 
Hazy 
6 5 2 Clear 
Sl. Cloudy 
Clear 
Clear 
Crystals 
0.15 
0.18 
Hazy 
7 5 4 Clear 
Sl. Hazy 
Clear 
Clear 
Clear 
0.20 
0.24 
Hazy 
__________________________________________________________________________ 
EXAMPLE 2 
Four 140 pound batches of degummed corn oil having 20 ppm phosphorus were 
bleached with 0.083% H.sub.3 PO.sub.4, 2.5% Filtrol 105 bleaching clay and 
various amounts of Filter Cel filtering aid varying from 0 to 0.25% by 
weight. In order to assess the effect of phosphorus level on filtration 
rate, the degummed oil in batch 2 was spiked with 5% crude corn oil. Half 
of each batch was filtered hot at approximately 176.degree. F. (80.degree. 
).) and constant pressure through a 1.26 square foot (0.117 square meter) 
Sparkler filter. The remaining half of each batch was cooled with 
agitation to 45.degree.-50.degree. F. (8.degree.-10.degree. C.) in 40-45 
minutes. The oil was then held at 50.degree. F. (10.degree. C.) for one 
hour before filtering through the same clean filter. A portion of oil from 
each hot filtration batch was used in a conventional dewaxing operation, 
which was designated as batch number 5 in the tabulated data which follows 
this example. The oil contained 0.75% filtering aid and no bleaching 
agent. Each oil was then subjected to a cold test at 0.degree. C., a 
refrigeration test at 7.degree. C., a room temperature test at 25.degree. 
C., and a turbidimeter test. The standards for each of these tests are the 
same as those specified in Example 1, with the additional requirement that 
the samples be clear in order to pass the room temperature test. The data 
obtained is tabulated in Table 2, which follows: 
TABLE 2 
__________________________________________________________________________ 
Turbidity Increase 
Filtration 
Cold Test .DELTA.NTU Hrs. at 
Batch Temperature 
Hrs. at 0.degree. C. 
0.degree. C. 
Samples 
Dewaxing 
.degree.C. 
3.5 24 48 144 1 2 24 44 
__________________________________________________________________________ 
*1A No 83-89 Hazy 
Hazy 
Crystals 
Crystals 
0.76 
1.09 
1.40 
1.49 
1B Yes 10-13 Clear 
Clear 
Clear 
Clear 
0.26 
0.22 
0.22 
0.23 
**2A No 89-92 Hazy 
Hazy 
Hazy Cloudy 
0.98 
1.37 
1.73 
1.83 
2B Yes 10-11 Clear 
Clear 
Clear 
Clear 
0.29 
0.29 
0.30 
0.32 
***3A No 87-90 Hazy 
Hazy 
Crystals 
Gel 0.79 
1.10 
1.43 
1.53 
3B Yes 10-13 Clear 
Clear 
-- -- 0.17 
0.17 
0.18 
0.19 
****4A 
No 86-91 Hazy 
Hazy 
Crystals 
Gel 0.71 
1.02 
1.33 
1.40 
4B Yes 10-11 Clear 
Clear 
Clear 
Clear 
0.23 
0.24 
0.23 
0.28 
5 Yes 8-9 Clear 
Clear 
Clear 
Crystals 
0.20 
0.19 
0.21 
0.23 
__________________________________________________________________________ 
Refrigeration 
Room Temperature 
Test Test 
Batch 
Days at 7.degree. C. 
Days at 25.degree. C. 
Samples 
1 2 13 2 3 14 
__________________________________________________________________________ 
1A Hazy 
Cloudy 
Gel Clear 
Clear 
Crystals 
1B Clear 
Clear 
Cloudy 
Clear 
Clear 
Clear 
2A Hazy 
Hazy 
Cloudy 
Clear 
Clear 
Crystals 
2B Clear 
Clear 
Clear 
Clear 
Clear 
Clear 
3A Hazy 
Hazy 
Cloudy 
Clear 
Clear 
Crystals 
3B Clear 
Clear 
Cloudy 
Clear 
Clear 
Clear 
4A Hazy 
Hazy 
Cloudy 
Clear 
Clear 
Crystals 
4B Clear 
Clear 
Crystals 
Clear 
Clear 
Clear 
5 Clear 
Clear 
Crystals 
Clear 
Clear 
Clear 
__________________________________________________________________________ 
*Batch 1 contained 2.5% bleaching clay and 0.5% filter aid. 
**Batch 2 contained 5% crude corn oil, 2.5% bleaching clay and 0.5% 
filter aid. 
***Batch 3 contained 2.5% bleaching clay and 0% filter aid. 
****Batch 4 contained 2.5% bleaching clay and 0.25% filter aid. 
EXAMPLE 3 
A crude corn oil was degummed by cooling it to 10.degree. C., mixing it 
with 3% cold water, and agitating the mixture at 10.degree. C. for 30 
minutes to achieve proper hydration of the gums and render them insoluble 
in the oil. The gums were then separated from the oil by centrifugation. 
The oil was dried in a falling film vacuum drier to reduce its moisture 
level to less than 0.1%, and was then divided into two samples. 
The first sample was placed in a 3 liter flask equipped with heating, 
agitation and vacuum, and reacted with 0.1% phosphoric acid (85% 
concentration) at 40.degree. C. for 15 minutes with continuous stirring. 
2.5% activated bleaching clay (Vega Plus.TM.) and 0.5% filter aid 
(Celatom.TM.) were added to the oil and the mass was heated to 100.degree. 
C. under vacuum of 50 mm Hg absolute pressure with intense stirring. The 
mixing at this temperature continued for 20 minutes. Afterwards, the 
vacuum was broken by sparging nitrogen into the flask and the oil was 
filtered through Whatman #41 filter paper in a Buechner funnel. 
The second sample of degummed oil was subjected to the same pretreatment 
with phosphoric acid and bleaching clay as the first sample. However, 
after heating at 100.degree. C. for 20 minutes, the mass was cooled to 
10.degree. C. in a water/ice bath and held at this temperature with 
agitation for 1 hour. The oil was then filtered in a chilled Buechner 
funnel through Whatman #41 filter paper. The bleached/dewaxed oil obtained 
was designated Sample 2. The clarity of both samples was compared during 
storage at 0.degree. C., 7.degree. C., and 25.degree. C. The results of 
this comparison are tabulated in Table 3 which follows. 
TABLE 3 
______________________________________ 
COMISON OF NON-DEWAXED 
AND IN-LINE DEWAXED CORN OILS 
Sample 1 Sample 2 
SAMPLE CODE NON-DEWAXED DEWAXED 
______________________________________ 
Cold Test 
Hrs. at 0.degree. C. 
18 hazy clear 
28 hazy clear 
48 hazy/turbid clear 
92 flocculent material 
clear 
Refrigeration Test 
Days at 7.degree. C. 
1 hazy clear 
2 turbid clear 
4 turbid clear 
Room Temperature Storage 
Days at 25.degree. C. 
1 crystals clear 
2 crystals clear 
4 turbid clear 
______________________________________ 
EXAMPLE 4 
A crude corn oil was degummed, dried and cooled to 40.degree. C. in a 
conventional manner. The degummed oil was then reacted with 0.08% 
phosphoric acid (85% concentration) under intense agitation for 20 
minutes. The pretreated oil was then pumped to a slurry tank and blended 
with 2.4% activated bleaching clay (Filtrol 105.TM.) and 0.8% filter aid 
(Celatom.TM.). The oil/clay mixture was then preheated to 105.degree. C. 
in a series of heat exchangers and then pumped to a vacuum bleacher 
operating under 50 mm Hg absolute pressure. After 30 minutes residence 
time in the bleacher, the mass was passed through several heat exchangers 
reducing its temperature at a rate of 10.degree.-20.degree. C. per minute, 
to 7.degree.-9.degree. C., then pumped to a crystal growth tank, where it 
was agitated for 1.5-1.7 hours residence time to crystallize waxy oil 
components. The cold mass of oil was continuously withdrawn from the 
bottom of the crystal growth tank and filtered in a pressure leaf type 
filter to separate a clear oil from the solids, which consisted of spent 
bleaching clay, filter aid and high melting point oil components. Six 
samples of the oil were tested, based upon different dewaxing 
temperatures. A control sample was also prepared by conventional dewaxing 
procedure involving bleaching corn oil by the same treatment as described 
above, filtering the bleached oil at 80.degree. C. to separate spent 
bleaching clay and filter aid, followed by cooling the clear bleached oil 
to 15.degree. C., mixing the chilled oil with 0.75% filter aid, to act as 
a seeding agent for crystallization of waxes, holding the mixture for 4 
hours in an agitated tank to achieve crystallization of waxes and other 
high melting oil components, followed by filtration in a plate and frame 
filterpress for separating clear oil from the solids. Clarity of each of 
the samples including the control sample designated as Sample 7 are 
tabulated in Table 4 which follows. 
TABLE 4 
__________________________________________________________________________ 
PLANT IN-LINE DEWAXING OF CORN OIL 
HOLDING 
TIME @ 
DEWAXING 
DEWAXING 
COLD TEST TURBIDITY INCREASE 
TEMP. TEMP. HRS. AT 0.degree. C. 
.DELTA.NTU; HRS. AT 0.degree. C. 
Sample 
.degree.C. 
HRS. 14 24 39 63 14 24 39 63 
__________________________________________________________________________ 
1 9 1.5 Clear 
Clear 
Hazy 
Hazy 
0.14 
0.23 
0.42 
0.47 
2 8.5 1.7 Clear 
Clear 
Clear 
Clear 
0.13 
0.13 
0.13 
0.13 
3 7 1.6 Clear 
Clear 
Clear 
Clear 
0.07 
0.06 
0.09 
0.09 
4 7 1.8 Clear 
Clear 
Clear 
Clear 
0.07 
0.06 
0.08 
0.07 
5 7.8 1.5 Clear 
-- Clear 
-- 0.07 
-- 0.09 
-- 
6 7.6 1.6 Clear 
-- Clear 
-- 0.08 
-- 0.10 
-- 
7 15 2 Sl. Hazy 
Hazy 
Hazy 
Hazy 
0.30 
0.41 
0.47 
0.51 
__________________________________________________________________________ 
EXAMPLE 5 
A degummed rapeseed (canola) oil with a residual phosphorus content of less 
than 30 ppm was bleached and in-line dewaxed according to the procedure 
described in Example 4. The specific parameters employed were: 
______________________________________ 
Pretreatment 
Oil flow rate 68 l/min. 
H.sub.3 PO.sub.4 0.09% 
Oil temperature 25.degree. C. 
Reaction time 20 min. 
Bleaching 
Amount of bleaching clay, 
2.7% 
Filtrol 105 .TM. 
Amount of filteraid, 
0.9% 
Celatom .TM. 
Temperature 110-118.degree. C. 
Time 30 min. 
Vacuum 50 mm Hg abs. pres. 
In-Line Dewaxing 
Temperature in crystal 
7-8.degree. C. 
growth tank 
Retention time 1.5 hours 
Filtration temperature 
10-11.degree. C. 
______________________________________ 
In a separate production run, the degummed rapeseed oil was subjected to a 
similar bleaching treatment as described above, however, it was hot 
filtered at 80.degree. C., and the in-line dewaxing step was omitted. Both 
samples were then compared for clarity on the basis of a cold test at 
0.degree. C. and turbidity measurement. This data is tabulated in Table 5 
which follows. 
TABLE 5 
______________________________________ 
COMISON OF IN-LINE DEWAXED 
AND NON-DEWAXED RAPESEED OIL 
TURBIDITY 
SAMPLE COLD TEST INCREASE, .DELTA.NTU 
DESCRIP- Hrs. at 0.degree. C. 
Hrs. at 0.degree. C. 
TION 1 2 24 48 1 3 4 
______________________________________ 
In-line clear clear clear 
clear 0.00 0.08 0.024 
dewaxed 
Non- hazy hazy -- -- 1.64 2.04 2.04 
dewaxed 
______________________________________