Saturated and Unsaturated Fat and Oils in food

Saturated and Unsaturated Fat and Oils in food

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  FATS AND OILS BY Dr.S.Mathangi AssistantProfessor of Home Science V.V.Vanniaperumal College for Women Virudhunagar
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  Introduction Fats and oilsbelongs to a group of organic compounds known as lipids. Oils and fats are natural occurring esters. Fats are found in animals. Oils are found in both animals and plants. Fats and oils are esters (fatty acids + glycerol) Fatty acids containing 12-18 Carbon atoms per molecule.
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  Fats and Oils Fatsare solid at room temperature while oils are liquid at room temperature. The melting points of fats are higher than the melting points of oils.
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  Saturated fats Fats whichcontain esters of glycerols and saturated fatty acids - saturated fatty acids : • has all carbon atoms joined together by single carbon-carbon (– C – C –) covalent bonds. Unsaturated fats Fats which contain esters of glycerols and unsaturated fatty acids : • contain single (– C – C –) and double ( – C = C – ) covalent bonds. Saturated and Unsaturated Fat
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  Differences between SaturatedFat and Unsaturated Fat
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  Sources of fat Animalfat Butter – made from churning creamIt provides 80g of fat per 100g.An alternative is ghee often used in Indian cooking (it is heated and then clarified). Lard – from pigs fat. It provides 99g of fat per 100g. It is usually softer than butter in consistency and white in colour. The quantity of lard depends on the location of fatty tissues in the animal and the method of heating. Suet – made from fat that surrounds animals organs, It has a similar fat content to that of lard.
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  Vegetable oils –mainly produced from oil seeds e.g. sunflower seeds or from the flesh of some fruits like olives. Ground nut oil Clear colored liquid Used exclusively in cooking Other oils Rape seed / mustard oil : Used as edible oil and as a lamp oil Sesame oil – Used as edible oil Coconut oil – Used in the preparation of soaps, vanaspathy and margarine. Also used as edible oil Soya bean oil –Can be used to get concentrated and isolated sources of protein Palm oil – Rich in β-carotene. Sources of fat
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  Emulsions are dispersionof one liquid in another liquid with which it is immiscible. Temporary emulsion: Oil + water shaken together – but on standing oil particles separate from water. Ex. French dressing rasam seasoned with oil. Emulsions
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  Emulsions Permanent emulsions: Apartfrom water and oil a 3rd substance called emulsifying agent or emulsifier is necessary to stabilize the emulsion. Stabilizer/ emulsifiers used as Egg yolk, Whole egg, Gelatine, Pectin, Starch paste, CaseinAlbumin and Fine powders such as Parika, Mustard Ex. Cake batter, Sambar, kitchedi, payasam – proteins starch and oil and Mayonnaise oil (liquid + lemon juice/vinegar (liquid + Egg yolk (lipo protein) emulsifying agent
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  Spoilage of fatsand oils Flavor reversion An objectionable flavour found before the onset of rancidity in refined oils when exposed to UV light, visible light or heating. The reaction is catalysed by O2 and small amounts of metals such as iron and copper Fats containing nucleic acid are most susceptible to reversion. Soya bean oil is mostly subjected to flavor reversion.
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  Prevention of reversion Hydrogenation
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  Prevention of reversion Hydrogenation
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  Rancidity Hydrolytic rancidity •Occurs dueto enzymes that decomposes fat in to free fatty acids (FFA) and glycerol. •Butyric acid and caproic acids are the volatile fatty acids, predominately present in butter are responsible for rancid flavour or odour in butter and makes butter inedible. •Long chain fatty acids such as stearic, palmitic and oleic acids do not produce rancidity unless oxidation occurs. •Heating thoroughly to destroy lipase catalyses hydrolysis of trans fats and prevents hydrolytic rancidity. •Certain microorganisms also produces lipase.
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  Oxidation •Unsaturated fats havelipoxygenase and are susceptible to oxidative changes. •Highly hydrogenated saturated fatty acids are resistant to oxidation. •Hydro peroxides that are formed readily producing smaller volatile substances will give characteristic odours of rancid fat.
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  • Storage atrefrigerator temperature prevents rancidity. • Light coloured glass containers absorb active rays and gives protection against spoilage. • Certain shades of green bottles, yellow transparent cellophane etc. prevents rancidity. • Vacuum packaging • Anti-oxidants naturally present in food such as vitamin ‘C’, β-carotene and vitamin E. Added antioxidants such as Butylated hydrogen anisole (BHA) Prevention of rancidity
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  Properties of Fatand Oils Aerates food – when fat is creamed with sugar it helps to trap air. Extends the shelf-life – makes the product last longer for baked products and it helps to retain the moisture in the product. Flavours and Odours – Gives foods such as biscuits a distinct taste and smell. Flaky texture to pastry – helps to separate the layers by creating steam. Emulsion – oils form an emulsion with liquids such as vinegar e.g. salad dressings. Colour – scones form a ‘shine’ once cookedHelps prevent lumps forming in a sauce. Shortening – Provides a shortening ability to the mixture and changes the texture. For example fats give shortbread its characteristic crumbly and short texture. It stops food from sticking and lubricates.