NST106-Lec6 - Lecture 6: Lipids 1 Significance in biology,...

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Lecture 6: Lipids 1 Significance in biology, nutrition, foods Properties of lipids important in foods Nomenclature of FA (Fatty Acids) Classification Chemical characterization Chemical composition – effects on properties FA composition – effects on properties Chemical reactions: hydrogenation
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Biology and nutrition • Energy source – high caloric density 9 kcal/g - in plants major energy reserve is CHO, plants don’t move - animals move –require a lighter source of energy reserve; migratory birds are excellent example, flying non-stop for days Mental exercise: 60 kg woman with 25% body fat = 15 kg fat ~30 kg CHO! additional 15 kg wt
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Biology and nutrition • Source of essential fatty acids • Carriers of fat-soluble vitamins • Components of membranes • Insulation • Hormones
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Functions in foods • Major components of “visible fat”: butter, margarine, cooking oil, salad oils, mayonnaise, lard • Components of “invisible fat”: milk, cheese, meat, fried foods, oil seeds
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Properties of lipids that are important in foods • Melting point- MP determines whether a lipid is oil or fat at room temp • Can be heated to high temp (150-230 o C) – a good cooking medium –allows browning of foods during frying • Can become rancid – 2 types of rancidity oxidative rancidity – oxidation by O 2 – leads to oxidized flavor, loss of EFA, generation of toxic cpds lipolytic rancidity – gives rise to free FA – more prone to oxidation, aroma of short chain FA • Ability to form emulsions with water and air lipid in water emulsion (milk, cream, salad dressing) water in lipid emulsion (butter, margarine) lipid in air emulsion (whipped butter, whipped cream)
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Fat is used as “shortening” in baked goods – gives a tenderizing effect, explained by ability to “lubricate”- interphases between proteins and CHO molecules making them slide past one another Contributes to flavor – intermuscular fat in meat gives the flavor unique to each species, lard contributes to meaty flavor, olive oil (rich in oleic acid) gives distinctive flavor to cuisine in Mediterranean countries, butterfat gives buttery aroma, peanut and sesame oil – preferred in Chinese cooking due to unique flavor Fat can be converted to soap – wash your dishes after eating!
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Nomenclature of
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NST106-Lec6 - Lecture 6: Lipids 1 Significance in biology,...

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