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Food, Nutrition and Health
FNH 340

Eggs Roles Texture-yolks give smooth, creamy feel (eg. Mousse) Flavour (eg. Custard), color. Whites toughen. Yolk fat -> shorten gluten -> tender Structure-b/c protein coagulates Binding-eg. Breaded meat-egg coagulates with heat -> breading sticks to meat Eg. Forms gel w/ heat -> binds milk in custard, holds meatloaf/burgers Clarify-white proteins coagulate + trap particles -> make clear eg. Broth, coffee Emulsify-yolk phospholipids let liquid combine w/ fat (usu. can’t) eg. Mayo Leaven-white PRO stretchable -> beat -> trap air -> expands, then hardens w/ heat Eg. meringue, soufflé, sponge cake, puffy omelette Interfering Agent-prevent ice crystals chunks from forming eg. candy, ice cream Structure Shell-colour depends on breed of hen-no effect on flavor; pores for air + moisture Bloom/Cuticle-shell coating that prevents bacteria contamination; washes away -some shells coated with edible oil to prevent losses -white/albumin-viscous, somewhat opaque, 57% of egg PRO; 2 shell membranes Yolk-33% fat; chalaza anchors it to albumin membrane + yolk’s vitelline membrane Proteins -high value, complete, standard for other foods Ovalbumin-globular, easily denatured, adds structure Ovotransferrin-binds Fe + inhibits Fe-dependent bacteria; heat-unstable if unbound Ovomucoid-heat-resistant Ovomucin-foam stabilizer; degrades as ages -> thinner whites Lysozyme-hydrolyzes bacterial walls; forms complex w/ ovomucin that thins whites Avidin-in white, binds biotin -> can’t absorb (only if eat 24 raw eggs/day); heat kills Lipoproteins-lipovitellin + lipovitellinin in yolk; help emulsify Phosvitin-a phosphoprotein Livitin-H20-soluble, contain sulfer CHO -very little; causes browning in fried/dry egg white (Maillard) Fats + Lipids -yolk fat =TG, PL, cholesterol (~213mg in large egg); amnt depends on diet (eg. Flax seed lowers cholesterol -> used for Born 3 eggs) Colloid-1 substance evenly dispersed in other -lecithin = emulsifier -> keeps cholesterol in colloid Vitamins + Minerals -shell has Ca, white has riboflavin (gives yellow/green colour) -yolks have fat-soluble vit. A + D, folic acid, pantothenic acid, B12. P, I, Zn, Fe (Fe absorption inhibited by phosvitin protein), S (stains silver + makes dark yolk ring) Pigments-color from carotenoids-depends on hen diet; doesn’t indicate vit. A value Flavour/Odor-affected by feed, envt, microorg. Invasion during storage Quality-based on genetics + breeding pH-fresh ~6 (white ~7.7) -> increases w/ age b/c CO2 + moisture lost (white ~9.4) Air Cell-fresh=small, usu. fixed -> sinks in water (expands with loss of moisture) White-thins w/ age b/c ovomucin degrades; less cloudy b/c CO2 leaves Vitelline-stretches/thins with age Chalazae-disintegrates -> yolk migrates (also b/c white thins) -> settles by shell Candling-pass eggs over light table; see shell quality, air cell, yolk, blood spots, mold Grading -Federal standards, Canada A1, A, or B; based on quality, not size -sizes are XL (75g), L (60), M (50), S (45) -> recipes use L (4 eggs=250mL) -weight, cleanliness, soundness, shell shape, yolk position, air cell, blood spots -grades free from discoloured yolks or blood spots (blood=very fresh) -grade As used for eg. Poached, fried eggs (looks matter) -grade B as liquid (omelet, quiche, baked goods) Refrigeration -during storage enzymes affect flavor, white thins, yolk absorbs moisture from white -can dip in mineral oil to reduce loss of CO2 + moisture -if subject to varying Ts, deteriorate (shouldn’t store in room or fridge door) -can store up to 6 months before being graded -cover to prevent uptake of odors/flavours; use within 4-5 weeks of pack date -in fridge yolks last 1-2 days, whites 4 days Freezing -can freeze up to 6 months -pasteurize to kill salmonella, maybe add stabilizer for yolks -salt, sugar, corn syrup usu. added (choose based on end use) to increase osmotic pressure + lower freezing point so solids retain liquid -cooked yolks + raw whites freeze well -cooked whole eggs/whites don’t freeze well -> ice crystals damage gel -> egg weeps -lipoproteins gel -> yolk viscous + gummy; water separates + forms crystals -> lipopro don’t reabsorb when defrosted -> thick, gummy Drying -spray dried yolks/whites have long 1 yr shelf life; 28g=2 lg eggs -glucose removed from whites via glucose oxidase or yeast fermentation -> prevent rxn w/ yolk cephalin (give off flavours) + Maillard rxn during storage -can combine w/ sugar or corn syrup to help w/ dispersion Safety -can have Salmonella from feces, hen, or handler -> don’t separate using shell -if need raw eggs, use pasteurized (eg. Salad dressing, mayo, eggnog) -bloom coating destroyed by heat/acid (once cooked, shell more porous -> bacteria) -cooking shrinks content -> -‘ve pressure -> draws in contaminants (refrig if cooked) -don’t keep at room T for more than 2 hours Cooking-Coagulation *Curdling/Syneresis-overheating causes PRO to shrink + liquid to separate Heat -> proteins bind H20 -> thicken/coagulate -> solids suspended in liquid = gel -> held by disulfide + H bonds Whites-coagulate at 60-65C; get soft, white, opaque; too hot -> tough, porous, shrink Yolks-65-70C; soft + mealy; too hot -> dry + crumbly (less likely to toughen, but will do so if yolk membrane ruptured from stirring) -coagulat
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