Fats and oils are come from both plant and animals source and have important functional and nutritional properties in foods.

1. Effects of cooking, processing &
storage of Fats and Oils

2. OVERVIEW..
 Edible fats and oils are come from both plant and
animal sources and have important functional and
nutritional properties in foods.
 Fats and oils can deteriorate in foods and are
susceptible to oxidation and rancidity.
 They also have shortening, lubricating, emulsifying
and whipping properties and high caloric value.

3. Continued..
• Fat have high melting point and are solid at room
temperature, whereas those have lower melting point and
are liquid at room temperature are called oils.
• Fats are present in many foods, this fat is often referred to
as invisible fat.
• Example of invisible fat; meat, poultry, fish, dairy product,
eggs, nuts and seeds.
• Examples of visible fats; lard, cooking oils, salad oils,
margarine and butter.

8. Changes in FATS during..
“HEATING”

9. “HEATING”
• Fats gradually soften on heating, they do not have a sharp
melting point.
• Smoke point, flash point and fire point : Smoke point of a
fat is the temperature at which smoke comes continuously
from the surface of the fat.
• When heated further smoke point, they flash and burn.
• The temperatures at which these occur are known as the
flash point and fire point.

10. TABLE showing different SMOKE
POINTS..
Fats oil Smoking Temperature (°c)
Butter 208
Cotton- seed oil 230
Coconut oil 138
Groundnut oil 149-162
Hydrogenated oil 221-232
Lard 194
Olive-oil made 176

11. EFFECTS..
• Pyrolysis (thermal breakdown): The action of heating the
oil, causes a breakdown in its molecular structure.
• When fat begins to smoke, its chemical breakdown begins
and free fatty acid and acrolein formed from glycerol, the
acrolein causes irritation in eyes and nostrils.
• Oxidation : Reaction of the hot oil surface with oxygen in
air causes molecular breakdown and development of
rancidity, results in offensive odours and flavours and
promotes polymerisation.

12. Cont..
• Hydrolysis : Free fatty acids are formed, when heat and
steam breaks a fatty acid molecule away from the glycerol
molecule.
• Reaction with food residues : Any food fragments left in oil
after cooking will undergo chemical reaction, particularly if
the oil is heated again without the residues being removed.
• Foods particles allowed to remain in the frying fat impact a
bitter, caramelized and burnt taste along with an
unappealing appearance to food fried.

13. Effect of prolonged heating on
nutritive value of fats and oils..
• It must be emphasized that continuous heating of fats and oils for
over eight hours results thermal oxidation.
• A number of factors may speed up the thermal deterioration. These
include use of large amounts of soya in the recipe, addition of
water to fryer during preparation to reduce the temperature and
addition of fats and oils left over from the day’s frying to the next
day’s lot and soon. In this manner, though the hours of frying in one
day may not be sufficient to causes thermal damages.

14. Changes in FATS during..
“COOKING”

15. “COOKING”
• The fat absorbed by the food undergoes greater changes than
the fat in which the food is cooked.
• Long cooking of fat increases the amount of decomposition of
fat.
• The higher the temperature to which the fat is heated, the
greater the decomposition product formed.
• Thus, during cooking, fat should not be heated higher than the
temperature needed for cooking.

16. EFFECTS..
• Polymerization : When fat is heated above 200C molecules
may unite to form long chain polymers.
• It is visible as deposits of a gum - like material around the
sides of frying equipment, especially where fat, metal and air
came in contact.
• Foaming : When polymerization is allowed to repeated
frying it causes foaming of fat, which decreases surface
tension and increases viscosity.

17. Cont..
• Hydrolytic breakdown : It tends to reduce interfacial
tension between fat and water from products being fried,
and also change in viscosity of these oil.
• This flavours penetration of fats into the foods makes
them greasy and non palatable.

18. Changes in FATS during..
“STORAGE”

19. “STORAGE”
• Darkness and coolness are not always possible when fats
are slipped and stored during the ordinary course of
commence.
• Vegetables fats, particularly those from seeds, show a
marked resistance to the onset of rancidity.
• Some seeds, if they are not bruised or crushed, can be
stored for years without any changes in the fats.
• In general, animal fats’ deteriorate fairly rapidly.

20. EFFECTS..
• Flavour Reversion : Fats undergoes a peculiar change before the
onset of rancidity. The characteristic flavour is lost and the fat or oil
has flat taste and a greasy feel on the tongue.
• This is known as flavour reversion and proceeds rancidity
changes.
• The factors which are known to development of reversion are
temperature, light, oxygen to a limited extent and trace
metals.
• As the temperature of storage in increased, the length of time in
which reversion flavour can be detected.

21. Cont..
• Rancidity : Spoilage of fats results in off flavour and renders the fat
inedible. These changes are known as rancidity.
• Fats and oils can get rancid by the action of air, water (hydrolysis) and
enzymes.
• Fats and oils slowly take up oxygen for a period of time before it is
possible to detect the flavour of the product of rancidity. This period is
called the induction period, and its followed by a second period in which
the uptake is much more rapid.
• Rapid oxidation can apparently take a number of paths. Temperature,
moisture, the amount of air in contact with the fat, light, particularly
that in the ultraviolet or near ultraviolet as well as the presence or
absence of antioxidants influences the reaction.

23. Processing of Oil and Fat
1. Rendering-
In this process, fat from animal tissue is extracted by heat.
Chopped or minced tissue are heated with water( wet
rendering)or its absence (dry rendering).
2.Pressing –
In this method of oil extraction by pressing is by the use of high
pressure expellers.
3.Solvent Extraction-
Pressed cakes contain appreciable quantities of oil.
Therefore, it is now common to extract oils by solvent extraction
or by combination of pressure and solvent extraction. With
material containing a low percentage of oil, it is only practical
method of removing oil.

24. Cont.......
4. Refining-
Oils extracted by the above methods are crude and contain
many other constituents like free fatty acids, unsaponifiable
matter,gums,waxes, mucilaginous matter, variety of colouring
matter, metallic contaminant, undesirable odoriferous
constituents etc. In refining, the suspended particles are
removed by filtration or centrifugation. The free fatty acids are
removed by alkali treatment.
5. Hydrogenation-
Refined oil on storage can become rancid. The unsaturated fatty
acid components of the oil undergo deteriorate changes with
time. To overcome this and to obtain fats of desired
properties, refined oils are hydrogenated.

25. 6.Vanaspati-
Hydrogenated oil is known as vanaspati in India. It
contains 95% hydrogenated oil to which 5% of a
liquid oil is added. In earlier days, groundnut oil
was used for hydrogenation and sesame oil as
the liquid component.
With the shortage of oil in country, more and more
nontraditional oils are being used in the
vanaspati industry.

26. Winterization
• Oils such as salad oils,or oils that are to be stored in cool
places undergo a process called winterization so that
they will not become cloudy when chilled .The refined,
deodorized oils are chilled with gentle agitation, which
causes higher melting fractions to precipitate.The
fraction which settles out is called stearin.Soybean oil
does not require winterization,out
canola,corn,cottonseed, sunflower,saffower and peanut
oils do.

27. Shortening fat
• Fat has a shortening power, that is, it interlaces between
protein and starch structures and makes them tear apart
easily. It makes the protein strands short rather than
allow them to stretch long.Thus,they tenderise baked
foods by preventing the cohesion of wheat gluten
strands and are used in making
biscuits,cakes,doughnuts,pastries and breads.The
different layers developed in puffs, and in (khari) biscuits
is due to the addition of fat which acts as shortening
agent.The fat added to maida dough results in soft roti
due to shortening property of fat.

28. Preservation
• There are many oils that store well, have multiple uses
around the home, and are ideal for cooking, storage and
emergency use.
• Follow these guidelines to store various kinds of fats and
oils for basic shelf life.
 Store fats and oils in their original containers.
 They are in air tight containers.
 If the container is cardboard, transfer the oil to glass jars.
 Store unopened containers in cool dark place like the
pantry, away from the stove or other appliances.
 If they solid in fridge, just leave them at room temperature
for a while before use and they will liquefy.

29. Nutritional Properties
• The quota for polyunsaturated fatty acids. In
particular,the ratio of omega-6 to omega-3 acids should
be between 5 and 10 to 1 (or less).Since the presence of
α-linolenic acid leads to oxidative instability and reduced
shelf life.
• Fats and oils have a high a high caloric value,2.25 times
more energy than carbohydrares or proteins.
• Each gram of fat contains 9 kcal of energy.
• Fats and oils carry the fat soluble vitamins,

30. REFERENCES..
• Wikipedia……………Google.
• Food science……….B.srilaxmi.
• Nutrition science…B.srilaxmi.