NUTR 211Exam # 3 Study Guide Fats and Oils Part 2A. melting point of fats1. influenced by the types of fatty acids and their positions on the glycerol backbone2. melting point raises with raised carbon length of fatty acid3. melting point decreases with increase in double bonds4. trans fatty acid higher melting point than cis counterpart5. cis bent, doesn’t pack; trans straight, packs6. high melting point= solid at room temp= relatively high percent saturated fatty acids/trans fatty acids7. low melting point= liquid at room temp= relatively high percent unsaturated fatty acids8. most of the fat in foods are triglycerides, which have a mix of different fatty acids9. as the temp of food lipids increase, different fatty acids melt at different temperatures B. plastic fats1. plasticity: the ability of a solid fat to be molded or shaped 2. two phase systema. most solid fats exist as an oil (liquid) suspended in a network of fat crystals (solid)3. the type and size of fat crystals influence consistency and performance of fat4. consistencya. ratio of solid to liquidb. type of crystals (alpha, beta prime, beta)c. fatty acid composition of fatd. temperature5. performancea. spreadabilityb. creamingc. pastry: solid fat separates starch and protein in flour 6. aids in aeration of betters and doughs, which contributes to leavening and lightness in bakedproductsa. solid fat creamed with sugarb. sugar crystals cut into solid fat and create air cellsc. air cells expand when batter/dough heatedC. emulsions1. a system consisting of one liquid dispersed in another liquid- usually immiscible2. two kinds of emulsions observed in food systemsa. oil-in-water: milk, cream, egg yolks, salad dressings, mayonnaise, cheese saucesb. water-in-oil: butter, margarine3. two phases of an emulsiona. dispersed or discontinuous phase (what is being suspended)b. dispersion or continuous phase (what is doing the suspending) c. interface: the boundary between the discontinuous phase and the continuous phase4. emulsifiers act as stabilizers5. stabilizers help keep one phase dispersed in the other6. by acting as surfactants at the interfacea. surfactants: wetting agents that reduce surface tension, which makes easier to mixb. surface tension: attractive property at surface of a liquid 7. amphiphilic: attracted to both water and fata. hydrophilic/polar: water-lovingb. lipophilic/nonpolar: water-opposing8. based on stability of the emulsion:a. temporary: least viscous and stable; will separate on standingb. semipermanent: stabilizers added; more viscousc. permanent: most viscous and stable; does not separate9. stability of emulsionsa. things you can do to decrease the stability of an emulsion:b. excessive agitationc. long storage timesd. extreme temperaturese. adding excessive salt10. natural emulsifiersa. lecithin from egg yolks or soyb. gelatinc. starchd. soy and milk productse. vegetable gums (carrageenan)f. mono and diglycerides (glycerol/OH hydrophilic)g. ground paprika, dry mustard, prepared mustard11. chemically prepared emulsifiersa. polysorbate 60b. propylene glycol monoestersD. heat transfer medium1. advantage of fat as heat transfer medium2. fryinga. pan frying: technique typically less than ½ in. fat/oilb. smoking oil is an indicator of decomposition> avoid thisc. butter, margarine, shortening, vegetable oil3. considerations for deep-fat fryinga. important to maintain oil temperature for high quality productb. when cold food is placed in fryer, how is temperature of oil affected?c. Monitor temp with thermostatic control or frying thermometerd. Don’t crowd fryer4. fat exposed to high temperatures changes chemically and physicallya. overheated fats reach ‘smoke point’b. the temperature at which a fat breaks down into visible gaseous products; different smoke point for different sources of fatc. flash point: temperature that volatiles from the fat ignited. fire point: temperature that substance will sustain continuous combustione. acrolein: produced in overheated cooking oils; glycerol cleaved from TG> dehydrated glycerol5. smoke points of fats/oils6. some degradation products of frying are surfactantsa. increases heat transferred to food and enhances fat degradationb. gums increase the viscosity of fat7. amount of fat absorbed by food is affected bya. temperature of fatb. percentage of fat and sugar and egg in productc. characteristics of foodd. type of fat doesn’t affect absorption, but condition of fat does8. choosing the right fat for fryinga. flavor should be stable to heatb. hydrogenation increases frying life of oilc. resistant to smoking at high temps (refined/deodorized)d. shortening without emulsifiers (mono and triglycerides)E. baking1. fats and oils tenderize baked products by shortening gluten strands2. interferes with gluten formation3. note- this is a different effect than the incorporation of air when plastic fats are creamed with sugar, which contributes to perception of tendernessF. fat deterioration (rancidity)1. hydrolytic ranciditya. breaking chemical bonds by adding water; yields glycerol and free fatty acidsb. short chain fatty acids common in butter- volatile, responsible for unpleasant odors and flavorsc. long-chain fatty acids such as steric, palmitic and oleic don’t usually produce rancid flavors from hydrolytic rancidity unless oidized 2. hydrolysisa. breakdown of triglycerides into glycerol and fatty acidsb. catalyst: heat and enzymes (lipases)3. oxidative ranciditya. chain reaction on unsaturated portion of fatty acidsb. heat, trace metals (zinc, iron, copper), salt, and light accelerate oxidative rancidity in fat4. antioxidants and the prevention of ranciditya. consumer controls: storage conditions like must refrigerate, exclude light, exclude moisture, exclude airb. food industry controls:c. antioxidants: natural-vitamin C, beta carotene, vitamin E; synthetic: BHA, BHT, TBHQ, and propyl gallated. citric acid: synergist with antioxidantse. chelating agents (sequestrants) bind trace amounts of metals (EDTA)Milk and Milk ProductsA. nutrient profile1. complete protein2. rich in B-vitamins and high in riboflavin and tryptophan 3. vitamins A&D4. excellent source of calcium, phosphorous, and potassiumB. composition of milk1. milk solids: 12.6%, water 87.4%2. fat: 3.7%, milk solids not fat: 8.9%C. disposition of milk1. milk exists as a a. solution: lactose, water soluble vitamins thiamin, riboflavin, niacin, and ascorbic acidb. colloidal dispersion: calcium, magnesium