2. Edible oil is basically plant or animal fat used in frying, baking, and
other types of cooking. Normally Cooking oil is typically a liquid,
although some oils that contain saturated fat, such as coconut
oil, palm oil and palm kernel oil, are solid at room temperature.
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3. Vegetable oils are classified into following 6 categories:
Major oils Nut oils Citrus oils
Coconut oil Almond oil Grapefruit seed oil
Corn oil Cashew oil lemon oil
Cottonseed oil Walnut oil etc. Orange oil etc.
Palm oil Other edible oils
Peanut oil Amarnath oil
Rapeseed oil Apricot oil
Safflower oil Avocado oil
Sesame oil Cocoa butter
Soybean oil Pressed mustard oil
Sunflower oil Okra seed oil
Mustard oil Papaya seed oil
Olive oil etc. Rice bran oil etc.
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4. Fat can be classified into two types:
Saturated Fat
Unsaturated fat
Under unsaturated fat we have,
Mono unsaturated fat(MUFA)
Poly unsaturated fat(PUFA)
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5. Immersion of food in hot oil for a period of time is called deep fat frying,
Carried out at a temperature b/w 165-185 deg. Celcius,
Moisture outflow from the food and oil absorption from the frying pan in
replacement of evacuated water takes place, and
Fast and convenient method of frying.
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6. Quick frying is obtained
It dehydrates food more quickly producing crunchiness of the product
Maillard reaction takes place producing required brown colors and
flavors
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7. Produces large amount of waste oil due to over heating or over using
leading to the formation of rancid tasting products of oxidation and other
deleterious, unintended or even toxic compounds such as
acrylamide(starchy foods).Indication of oil includes
darkening,smoke,foaming,thickening,rancid taste and unpleasant smell
when heating.
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8. Quality Index Sunflower Oil Soybean Oil
Oil color Pale yellow Faint green
FFA value 0.561 0.673
Iodine value 120-145 120-136
Peroxide value 0.7 mmol/kg oil <= 10.0
meqO2/kg oil
Soap value 188-194 190
Moisture content 9-10% 8-16%
Density 918.8 kg/m3 916.5 kg/m3
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9. a) Determination of Acid value(FFA test):
This test determines the amount of free fatty acid in oil/fat in terms of
acid value.
Definition:
Acid value is defined as the number of milligrams of KOH required to
neutralize the FFA present in one gram of fat.
Principle:
The acid value is determined by directly titrating the oil/fat in an
alcoholic medium against standard NaOH/KOH solution.
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10. b) Determination of Iodine value:
Definition:
The Iodine value of an oil/fat is the number of grams of iodine absorbed
by 100 grams of oil/fat. The iodine value is the measure of unsaturation
in oil/fat.
Principle:
The oil/fat sample taken in chloroform is treated with a known excess of
iodine monochloride solution. The excess of iodine monochloride is
treated with potassium iodide and the liberated iodine estimated by
titration with sodium thiosulfate solution.
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11. c) Determination of Saponification value:
Definition:
Saponification value represents the number of milligrams of potassium
hydroxide required to saponify 1g of fat under the conditions specified.
Principle:
Fats (triglycerides) upon alkaline hydrolysis (either with KOH or NaOH)
yield glycerol and potassium or sodium salts of fatty acids (soap).
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12. d) Determination of peroxide value:
Definition:
Peroxide value is a measure of the concentration of peroxides and
hydroperoxides formed in the initial stages of lipid oxidation.
Principle:
Milliequivalents of peroxide per kg of fat are measured by titration with
iodide ion. High peroxide values are a definite indication of a rancid fat,
but moderate values may be the result of depletion of peroxides after
reaching high concentrations.
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13. e) Determination of moisture content:
Procedure:
Weigh previously dried sample of oil/fat of 5-10 gm. over a balance.
Put the sample in a dish and heat in an oven at 105 degree C.
Cool in a desiccator containing phosphorus pent oxide and weigh.
Heat in the oven for further one hour, cool and again weigh.
Repeat this process of heating, cooling and weighing until change in
weight between two successive observations does not exceed 1 mg.
Calculation:
Moisture and volatile material= (W1*100)/W
Where, W1= Loss of material in drying in gram
W= Original weight of the sample oil/fat
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14. f) Determination of specific gravity:
Preparation of sample:
Melt the sample if necessary. Filter through a filter paper to remove any
impurities or physical contaminations. Make sure that sample is
completely dry. Cool the sample to room temp.
Apparatus:
Picnometer fitted with a thermometer of suitable range with 0.1 or 0.2
subdivisions. Water bath maintained at 300.2 degree C.
Procedure:
Fill the dry Picnometer with the prepared sample in such a way to
prevent entrapments of air bubbles after removing the cap of the side
arm.
Insert the stopper, immerse in water bath at 300 degree C and hold for 30
minutes.
Carefully wipe off any oil that has come out of the capillary opening.
Remove the bottle from the bath, clean and dry it thoroughly.
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15. Remove the cap of the side arm and quickly weigh ensuring that
temperature does not fall below 30 degree C.
Calculations:
Specific gravity at 30 degree C= (A-B)/(C-B)
Where;
A= Weight in gram of specific gravity bottle with oil at 30 degree C
B=Weight in gram of specific gravity bottle at 30 degree C
C=Weight in gram of specific gravity bottle with oil at 30 degree C
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16. Review-I
Zahir et al. (2014) studied physiochemical properties of edible oil like
density, viscosity, boiling point, saponification value, iodine value &
peroxide value of corn and mustard oils & investigated the effects on the
use of same oil for repeated frying to find the changes in the
physiochemical, nutritional & sensory properties of oil. FT-IR
spectroscopy was used to evaluate the degree of oxidation after heating &
frying process. The results revealed that due to the temperature change in
oil there is notable difference in the spectral band which showed that the
proportions of fatty acids were changed. They find that the spectra of
corn oil at the boiling point & at multiple frying times with a piece of
potato showed frequencies in range of 2852.7-2926.0/cm while in mustard
oil an additional peak was observed at 3633.8/cm which exhibits the
secoundary oxidised product formation.
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17. Review-II
Tsuzuki et al (2010) studied formation of trans fatty acids in edible oil
during the frying & heating process to assess an impact of heated edible
oils on intake of trans fat. For the frying model, sliced raw potatoes were
fried in commercially available canola oil at 160, 180 & 200 deg. celcius., &
the 10 frying cycles were performed. The TFAs contained both in fried
potatoes & in frying oils were measured by gas chromatography. It was
found that the lipid content & TFAs in the raw potatoes were negligible.
On the other hand, fried potatoes contained lipids at the level of (8.8-
9.2)% & the fatty acid composition was mostly in correspondence with
that of frying oil. After 10 frying operations, TFAs content, acid values &
peroxide values of the frying oils were measured & compared with those
of corresponding heated canola oils without food. He found that the
amounts of trans 18:1 FAs contained both in frying oil & in heated oil
were less than the quantitative limit(0.047g/100g oil). But there was an
increase of trans 18:2 & 18:3 FAs of the used frying oil were 0.02g/100g &
0.05 g/100g,respectively compared with those of the fresh oil. From the
above results he suggested that an ordinary frying process using
unhydrogenated edible oils has little impact on TFAs intake from edible
oils.
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18. Review-III
Sebestian et al ( 2014) examined quality & safety of fresh, in use &
discarded frying oils from randomly selected restaurants in downtown
Toronto, Canada, in order to assess the oxidative & hydrolytic state of oil
used in commercial practice & consumed regularly by the local
population. She found that all in-use & discarded samples have high
levels of oxidation products based on the p-anicidine value (p-AV)
(7.6<p-AV<56.5) & high peroxide value (PV>10 meq/kg) & free fatty acid
levels (FFA>1%) suggested that 30-35% of in-use frying oils & 45-55% of
discarded oils were not acceptable.
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19. (1) Zahir E., Saeed Rehana, Hameed M.A. and Yousuf A. (2014), Study of
physicochemical properties of edible oil and evaluation of frying oil
quality by FT-IR Spectroscopy, Arabian Journal of Chemistry, In Press
(2) Tsuzuki W., Matsuouka A. and Ushida K. (2010) Formation of Trans-fatty
acids in edible oils during the frying and heating process, Food
Chemistry, 123, pp-976-982
(3) Sebastian A., Ghazani S. M. and Marangoni A. G. (2014) Quality and
safety of frying oils in resturants, Food research International, 64, pp- 420-
423
(4) www.google.com
(5) www. wikipedia.com
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