importance of fats and oil

1. Oils and fats, importance, uses
and sources
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2. Terms
 Fat: Triester of long chain of saturated fatty acids with glycerol. E.g. Wool Fat
 Oil: Triester of long chain of unsaturated fatty acids with glycerol. E.g. Olive oil
 Lipids: Triester of longchain fatty acids with glycerol
 Fatty acid: Long chain of carboxylic acid are known as fatty acid
 Saturated fatty acids: that contains carbon-carbon single bond inside chain of
carboxylic acid. E.g. stearic acid
 Unsaturated fatty acids: contains one or more carbon-carbon double bonds
inside chain of carboxylic acid e.g. oleic acid
 Wax: Esters of fatty acids with high molecular weight monohydric alochol
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3. Oils and fats
 Oils and fats are important nutrients in a healthy diet
 Structurally, they are esters of glycerol with three fatty acids. As such, they are
scientifically called triacylglycerols but are commonly referred to in the food
industry as triglycerides
 Although the terms 'oils' and 'fats' are often used interchangeably, they are
usually used to distinguish triglycerides in the liquid state at ambient
temperatures (oils) from those in the solid state (fats)
 Oils and fats are commonly either of vegetable origin (e.g. palm oil, rapeseed
oil, soybean oil, olive oil, cocoa butter, etc.) or animal origin (e.g. pork lard,
beef tallow, fish oils) as well as from animal milk fats.
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4. Cont…
 The fatty acids found in most commonly consumed oils and fats are composed
of long carbon and hydrogen chain
 Typically containing from 8 to 20 carbon atoms, mainly with even numbers of
carbon atoms
 Animal fats also contain significant levels of odd-chain fatty acids. They have
a methyl (CH3) group at one end and a carboxylic acid (COOH) at the other
 Fatty acids can be grouped into four main types:
 Saturated
 Monounsaturated
 Polyunsaturated
 Trans
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5. Saturated fatty acid
 Saturated fatty acids are straight chains of carbon atoms consisting of
methylene (CH2) groups between the end methyl and carboxylic acid groups.
 The most common saturated fatty acids are lauric acid (C12), palmitic acid
(C16) and stearic acid (C18).
 Shorter chain saturated fatty acids are found in butterfat (e.g. C4, butyric acid)
and coconut oil (e.g. C8, caprylic acid, and C10, capric acid).
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6. Monounsaturated fatty acid
 Monounsaturated fatty acids contain a single carbon-carbon double bond in the
carbon chain, this is usually in the cis configuration
 The most common monounsaturated fatty acid is oleic acid, containing 18
carbon atoms. In oleic acid, the double bond is between carbon atoms 9 and 10
(counting from the COOH group)
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7. Polyunsaturated fatty acid
 Polyunsaturated fatty acids have more than one double bond in the carbon
chain
 Common polyunsaturated fatty acids are;
 Linoleic acid (18 carbon atoms and 2 double bonds between carbon atoms
9/10 and 12/13)
 Linolenic acid (18 carbon atoms and 3 double bonds between carbon atoms
9/10, 12/13 and 15/16)
 In these two examples, the first double bond to be encountered in linoleic acid
is at the sixth carbon atom and, for this reason, linoleic acid is also called an
omega-6 polyunsaturated
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8. Cont…
 In linolenic acid, the first double bond is at the third carbon atom and so
linolenic acid is called an omega-3 polyunsaturated
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9. Classification of PUFA
 PUFA can be further categorized into three main families according to the
position of the first double bond starting from the methyl-end of the fatty acid
chain:
 Omega-3 (or n-3) fatty acids have the first double bond at the third
carbon atom and include mainly alpha linolenic acid (ALA) and its
derivatives eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
 Omega-6 (or n-6) fatty acids have the first double bond at the sixth carbon
atom and include mainly linoleic acid (LA) and its derivative arachidonic acid
(AA).
 Omega-9 (or n-9) fatty acids have the first double bond at the ninth carbon
atom and include mainly oleic acid.
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10. Trans fatty acid
 Trans fatty acids, are also unsaturated but, in this case, some or all of the
double bonds are in the trans configuration
 They can gradually be produced and build up in used frying oils
 Trans fatty acids are also found naturally in the milk and meat of ruminant
animals such as cattle
 Typical natural trans fatty acid levels in cow’s milk are about 5%, although
levels as high as 9%
 The trans fatty acids in milk are mainly vaccenic acid (a trans-
monounsaturated with a double bond between carbon atoms 11 and 12)
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11. Cis vs Trans
 Partial hydrogenation has a down-side. Natural unsaturated fatty acids are in
configuration that is called cis.
 Partial hydrogenation can flip the chemical bonds into a different configuration
that is called trans.
 The difference between cis and trans is that, in cis configuration the two H-atoms
are on the same side of the double bond.
 While in trans configuration H-atoms are on opposite sides.
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12. Importance
 The most concentrated source of food energy
 There are 9 calories in every gram of fat
 Fats that are liquid at room temperature are called oils. E.g. vegetable oil, canola
oil, etc.
 Fats that are firm at room temperature are called solids. E.g. Lard, shortening,
etc.
 It is recommended that the maximum number of grams of fat a person should
have in a day is 66 grams.
 No more than 30% of a person’s total calories should come from fat sources.
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13. Cont…
 No more than 10% (22 grams) of the total fat should come from saturated fat
 20% (44 grams) should be from monounsaturated and polyunsaturated fat
sources
 Fats also carry and help the body absorb the fat soluble vitamins A, D, E and
K
Cholesterol:
 Cholesterol is NOT fat
 It is a “fat-like” substance present in all body cells that is needed for many
essential body processes
 It contributes to the digestion of fat and the skin’s production of vitamin D
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14. Ten of the Most Important Functions
That Fats and oils Serve in Food
1. Appearance
 Fats and oils can alter a food’s appearance by creating a glossy or moist visual
texture
 The ability of fat to refract light is also responsible for the opaque appearance
of milk.
 Fats also aid in the browning process of many foods, giving them an appealing
golden brown color.
2. Emulsions
 Fats and oils are an important component in most emulsions.
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15. Cont…
 Emulsions are the dispersion of a fat or oil into water (or vice versa) O/W or
W/O.
 There are many emulsions in the culinary world including salad dressings,
mayonnaise and cheese sauces.
 Emulsifying fat into a liquid produces unique flavor and texture qualities.
3. Flavor
 Fat has the unique ability to absorb and preserve flavors.
 Fats also contain compounds that lend specific flavors of their own.
 The way fat coats the tongue and allows flavors to linger can also alter a flavor
experience.
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16. Cont…
 The species-specific flavors of meats are carried in their lipids; the flavors of
beef and lamb are indistinguishable, if the lipids are stripped from the meats
4. Heat Transfer
 Fats provide one of the most efficient modes of heat transfer during cooking.
 From deep fat frying to sautéing in a skillet or wok, hot oil is able to transfer
high levels of heat to the surface of food without over heating the interior
portions.
 Using fats and oils to transfer heat also facilitates crust formation.
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17. Cont…
5. Melting Point
 The type off at used in a product often determines the melting point of the final
product.
 A melting point is the temperature at which a substance changes from a solid to
a liquid.
 This characteristic is especially important for items like chocolate, frosting and
salad dressings.
 Saturated fats, like butter and animal fats, are solid and room temperature,
which make the imperfect for using solid foods like chocolate and frosting.
 The low melting point of vegetable oils allows salad dressings to stay in liquid
form when refrigerated
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18. Cont…
6. Nutrition
 Fats are the most calorie dense compound in food, weighing in at over twice
the calories per gram of proteins or carbohydrates.
 While this may not be seen as an advantage in today’s modern society, the
ability to provide energy dense food items is still necessary in many parts of
the world.
 Fat is an effective method of delivering calories when needed.
 Fats are also important for delivering fat-soluble vitamins such as Vitamins A,
E, D and K.
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19. Cont…
7. Satiety
 Fats play an important role in making foods satisfying or making us feel full.
 Because fats take longer to digest than carbohydrates or proteins, high-fat foods
stay in the stomach longer and delay the feeling of hunger.
8. Shortening
 Shortening is not just the name of a solid, shelf stable fat but it is also the term
used to describe fat’s ability to make baked goods tender by impeding the
formation of gluten strands.
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20. Cont…
 Normally, as bread dough is kneaded the gluten (wheat protein) begins to join
and form long elastic strands, which give strength and a chewy texture to the
bread.
 When fat is added to dough, like in biscuits and pie crusts, the fat gets in the way
of the gluten formation, therefore keeping the final product tender and flakey.
9. Solubility
 While fats and oils are not soluble in water, there are other chemical compounds
that are only soluble in fats.
 Many of these fat-soluble compounds are responsible for foods flavor and even
vitamin content.
 Including fat in food allows for maximum flavor and a wide range of nutritional
content
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21. Cont…
10. Texture
 Fats and oils have a texture all their own but are also responsible for
tenderizing baked goods via the shortening process.
 Fat provides a very specific, lubricating mouthfeel, which is why most dry
crackers or chips are served with high-fat content dips or spreads.
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22. Uses of fats and oils
 Fats and oils are used throughout the world for both food applications and
industrial uses
 They are consumed in butter, shortening, margarine, salad oils, and cooking
oils, as well as in animal feeds, fatty acids, soaps, personal care products,
biodiesel, paints (made from alkyd resins), lubricants, and greases.
 The sources of fats and oils include edible vegetable oils, palm oils, industrial
oils, animal fats, and marine oils.
 Food applications account for the major share (about three-fourths) of the
worldwide consumption of fats and oils.
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23. Sources of Fats and Oils
 Edible fats and oils are obtained from three main sources:
i. Vegetable
ii. Animal
iii. Fish
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24. Vegetable oils
 These are derived from seeds of plants which grow in many parts of the world
but mainly in tropical and sub tropical regions. The main vegetable oils are
obtained from the following
1. Coconut palm
 The coconut is harvested when ripe, the outer fibrous husk is removed and the
nut exposed.
 This is then cut in half, exposing the thin white fleshy layer known as the
‘meat’.
 This is the endosperm of the nut. This may be eaten raw or processes into
products such as desiccated coconut, or dried in the sun or in kilns.
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25. Cont…
 When dried it is known as copra in which state it is exported to countries who
extract and refine the oil. The main sources of supply are the Philippines,
Malesia and Sri Lanka.
2. Olive oil
 The ripened fruit of the olive tree produces one of the finest of all vegetable
oils.
 The first crushing of the fruit gives the highest grade oil which needs no
refining.
 It is exported mainly by Italy, Spain and Greece.
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26. Cont…
3. Groundnut or Peanut Plant
 The plant produces pods containing the nuts a few inches below the
surface of the soil, which makes harvesting more complicated than
for those sources previously mentioned.
 It is exported as nuts, and as oil, by such countries as Nigeria, West
Africa and China.
4. Soya Bean
 The soya plant, a member of the pea family, produces many pods
which each contain three to four beans on each plant.
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27. Cont…
 It is one of the most widely consumed cooking oils
 Although relatively low in oil content (between 13-20 per cent)
 Soya bean has recently become the leading sources of vegetable oil in the
world.
 It is mainly exported by the U.S.A, China and Brazil.
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28. Cont…
5. Sun flower oil
 Sunflower oil is the non-volatile oil pressed from the seeds of
sunflower (Helianthus annuus).
 Sunflower oil is commonly used in food as a frying oil, and in
cosmetic formulations as an emollient.
 Sunflower oil is primarily composed of linoleic acid, a
polyunsaturated fat, and oleic acid, a monounsaturated fat.
 The expressed oil has light amber color with a mild flavor. The oil is
rich in vitamin E content.
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29. Animal Fats
 Animal fats are one of the many by products from the slaughtering of animals
for human consumption
 Fat in animals occurs naturally and is found mainly as a layer under the skin
 Surrounds and protects vital organs of the body such as the kidney and the
intestine
 The three main sources are from the following
i. Beef
ii. Sheep
iii. Pig
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30. Cont…
1. Beef Animals
 These are the largest of animals commonly slaughtered for human
consumption and a high quality fat is obtained as a by-product
 Suet is obtained from around the kidneys and shredded
 The intestinal fat is processed at low temperature to produce two products,
oleo stearin and also oil, both of which can be used in the manufacture of
margarine.
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31. Cont…
2. Sheep
 Very small quantities of sheeps fat are used.
 This is mainly because the fat tends to be harder than beef or pork
fat and has a stronger flavour and odour.
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32. Fish Oils
 These are obtained by the extraction of oil from the whole fish.
 The fish most suitable are those with a high fat content and these are mainly
herring, pilchard, sardines, and anchovies.
 Unfortunately these are unsaturated oils and are susceptible to oxidative attack
and must therefore be carefully refined and hydrogenated before being used in
margarine and cooking fats.
 Fish oil is encapsulated to prevent oxidation and for the ease of consumption.
 Fish oils are imported form Peru, Norway and Iceland.
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