TAMU NUTR 211 - Exam 3 Study Guide (12 pages)

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Exam 3 Study Guide

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Exam 3 Study Guide


Study Guide
Texas A&M University
Nutr 211 - Scientific Prin Of Foods
Scientific Prin Of Foods Documents
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NUTR 211 Exam 3 Study Guide Fats and Oils Part 2 A melting point of fats 1 influenced by the types of fatty acids and their positions on the glycerol backbone 2 melting point raises with raised carbon length of fatty acid 3 melting point decreases with increase in double bonds 4 trans fatty acid higher melting point than cis counterpart 5 cis bent doesn t pack trans straight packs 6 high melting point solid at room temp relatively high percent saturated fatty acids trans fatty acids 7 low melting point liquid at room temp relatively high percent unsaturated fatty acids 8 most of the fat in foods are triglycerides which have a mix of different fatty acids 9 as the temp of food lipids increase different fatty acids melt at different temperatures B plastic fats 1 plasticity the ability of a solid fat to be molded or shaped 2 two phase system a 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 fat 4 consistency a ratio of solid to liquid b type of crystals alpha beta prime beta c fatty acid composition of fat d temperature 5 performance a spreadability b creaming c pastry solid fat separates starch and protein in flour 6 aids in aeration of betters and doughs which contributes to leavening and lightness in baked products a solid fat creamed with sugar b sugar crystals cut into solid fat and create air cells c air cells expand when batter dough heated C emulsions 1 a system consisting of one liquid dispersed in another liquid usually immiscible 2 two kinds of emulsions observed in food systems a oil in water milk cream egg yolks salad dressings mayonnaise cheese sauces b water in oil butter margarine 3 two phases of an emulsion a 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 phase 4 emulsifiers act as stabilizers 5 stabilizers help keep one phase dispersed in the other 6 by acting as surfactants at the interface a surfactants wetting agents that reduce surface tension which makes easier to mix b surface tension attractive property at surface of a liquid 7 amphiphilic attracted to both water and fat a hydrophilic polar water loving b lipophilic nonpolar water opposing 8 based on stability of the emulsion a temporary least viscous and stable will separate on standing b semipermanent stabilizers added more viscous c permanent most viscous and stable does not separate 9 stability of emulsions a things you can do to decrease the stability of an emulsion b excessive agitation c long storage times d extreme temperatures e adding excessive salt 10 natural emulsifiers a lecithin from egg yolks or soy b gelatin c starch d soy and milk products e vegetable gums carrageenan f mono and diglycerides glycerol OH hydrophilic g ground paprika dry mustard prepared mustard 11 chemically prepared emulsifiers a polysorbate 60 b propylene glycol monoesters D heat transfer medium 1 advantage of fat as heat transfer medium 2 frying a pan frying technique typically less than in fat oil b smoking oil is an indicator of decomposition avoid this c butter margarine shortening vegetable oil 3 considerations for deep fat frying a important to maintain oil temperature for high quality product b when cold food is placed in fryer how is temperature of oil affected c Monitor temp with thermostatic control or frying thermometer d Don t crowd fryer 4 fat exposed to high temperatures changes chemically and physically a 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 fat c flash point temperature that volatiles from the fat ignite d fire point temperature that substance will sustain continuous combustion e acrolein produced in overheated cooking oils glycerol cleaved from TG dehydrated glycerol 5 smoke points of fats oils 6 some degradation products of frying are surfactants a increases heat transferred to food and enhances fat degradation b gums increase the viscosity of fat 7 amount of fat absorbed by food is affected by a temperature of fat b percentage of fat and sugar and egg in product c characteristics of food d type of fat doesn t affect absorption but condition of fat does 8 choosing the right fat for frying a flavor should be stable to heat b hydrogenation increases frying life of oil c resistant to smoking at high temps refined deodorized d shortening without emulsifiers mono and triglycerides E baking 1 fats and oils tenderize baked products by shortening gluten strands 2 interferes with gluten formation 3 note this is a different effect than the incorporation of air when plastic fats are creamed with sugar which contributes to perception of tenderness F fat deterioration rancidity 1 hydrolytic rancidity a breaking chemical bonds by adding water yields glycerol and free fatty acids b short chain fatty acids common in butter volatile responsible for unpleasant odors and flavors c long chain fatty acids such as steric palmitic and oleic don t usually produce rancid flavors from hydrolytic rancidity unless oidized 2 hydrolysis a breakdown of triglycerides into glycerol and fatty acids b catalyst heat and enzymes lipases 3 oxidative rancidity a chain reaction on unsaturated portion of fatty acids b heat trace metals zinc iron copper salt and light accelerate oxidative rancidity in fat 4 antioxidants and the prevention of rancidity a consumer controls storage conditions like must refrigerate exclude light exclude moisture exclude air b food industry controls c antioxidants natural vitamin C beta carotene vitamin E synthetic BHA BHT TBHQ and propyl gallate d citric acid synergist with antioxidants e chelating agents sequestrants bind trace amounts of metals EDTA Milk and Milk Products A nutrient profile 1 complete protein 2 rich in B vitamins and high in riboflavin and tryptophan 3 vitamins A D 4 excellent source of calcium phosphorous and potassium B composition of milk 1 milk solids 12 6 water 87 4 2 fat 3 7 milk solids not fat 8 9 C disposition of milk 1 milk exists as a a solution lactose water soluble vitamins thiamin riboflavin niacin and ascorbic acid b colloidal dispersion calcium magnesium phosphates citrate and proteins are colloidally dispersed in the aqueous phase of milk c emulsion fat is present as small globules or droplets D milk proteins

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