FDNS 1301 Introduction to Foods Eggs and Egg Cookery Composition * three basic parts or components 1) shell 2) egg white 3) egg yolk Shell * mostly calcium carbonate * shell is porous (diffusion of carbon dioxide and moisture out over time) * cuticle / bloom protects against bacteria * air space separates cuticle and shell * 9 to 12 % total weight of egg Egg Whites * also known as albumen (protein) * able to hold air when beaten * four different layers of different thickness' * food and moisture source for embryo * chalazae (kuh-LAY-zah) is anchor for yolk in center * approximately 60% of total weight of egg Egg Yolk * Location of all fat, most calories, vitamins and minerals * concentric layers of light and dark * salmonella located in this portion * forms remaining 30 to 33% weight of egg Egg Quality and Sizing * quality declines greatly over time * yolk sits high when young * over time, yolk stretches and flattens (due to water absorption) * whites transfer water (from diffusion to the atmosphere and yolk) from thick to thin * lower volume when beaten * chalazae disintegrates * no longer holds yolk in center * lost of moisture through shell * air cell increases over time * egg loses carbon dioxide, increased alkalinity * egg may absorb flavors from fridge Weight Classes Weight Class Minimum Weight/dozen Jumbo 30 oz Extra Large 27 oz Large 24 oz Medium 21 oz Small 18 oz Peewee 15 oz Grading AA Quality * best or highest grade * solid shell * small air cell * firm clear whites * no yolk defects * preferred for poaching, frying and cooking within the shell A Quality * second grade * shell still intact * reasonably firm white * outline of yolk and white layers fairly well defined * larger air cell * moderate spread when broken * suitable for all cooking B Quality * lowest grade * shell abnormal, slightly stained * larger air cell * watery egg white(larger spread) * may have blood / meat spots * yolk outline very visible, enlarged and flattened * sometimes visible germ development * scrambled eggs, baking or used as an ingredient in another product Storage and Handling * refrigeration at 40F or below in original case * purchase from refrigerated sources only * inspect and discard broken * ensure grade and size is clearly marked on cases * shelf life approximately 2 weeks Freezing Eggs * gelation occurs in the egg yolk after thawing (lipoproteins with increased salt concentration) * sugar added to absorb free water (1%) * no effects on egg whites Denaturation Definition * alteration from natural ordered conformation to a randomly structure molecule * also known as uncoiling Denaturation caused by 1) heating 2) mechanical beating 3) acidity 4) salt concentration 5) freezing 6) Mallard Browning reaction * browning reaction using a combination of sugars and proteins * occurs in foods heated to high temperature or foods in storage for long periods Coagulation * proteins crossbond with each other forming a rigid structure * very similar to gelation * overcoagulation shrinks protein structure, resulting in weeping or syneresis * occurs over range of temp. * whites from app. 140 F to 152 F * yolk from 145 F to 158 F * whole eggs at 156 F * whole eggs and liquid at 175-185 F Four factors affect coagulation 1. Concentration * diluted eggs increases time needed for coagulation (proteins spread out) 2. Rate of Heating * rapid heating coagulates protein at higher temperatures (less time for denaturation to occur) * close to curdling temperature 3. Added Substances * sugars increase temp. needed for coagulation (increased heat stability) * acid lowers coagulation temp. (lower time) * salts aid in coagulation (bond formation) 4. Time/Temperature * rate of coagulation increases with temperature * coagulum formed is firmer at higher temp. Egg Foams * egg proteins aid in formation * beating lower surface tension and denature protein * coagulate at interface point forming network * egg whites beaten change color (greenish to yellow/translucency) * stiffness and volume increase over time * surface changes from glossy to dry/dull Various stages of foams * Soft, underbeaten has large bubbles (unstable) * not enough structure to hold liquid on standing (weeping) * overbeaten appears dry, dull, curdled * protein overcoagulated, no elasticity * bubbles coalesce, liquid weeps Factors affecting Foam 1. Type of equipment used (fine wires = fine air cell) * Type of mixing bowl used 2. Sugar addition (at the beginning) * lengthens time to beat foam, produces smaller volume 3. Storage Conditions * fresher eggs produce greater volume (protein adulteration) 4. Temperature * increased volume at room temperature (1 hour) * lowered surface tension and viscosity 5. Acids increase stability * delays formation but produces more bond structure 6. Salt * flavor enhancer * decreases stability over short term, no effect on long term 7. Sugar * delays surface coagulation, longer time to form formation * protects against overbeating * smoother, more shiny and stable 8. Fats * totally inhibits stable foam formation * clean all equipment * wipe with towel dipped in acid (lemon juice) Meringues * two types 1) soft meringue (pies) 2) hard meringue (shells for pies, ice cream) Meringue Problems * fluid leaking from baked soft meringue * product undercoagulation by temperature * beading (droplets) due to overcoagulation * ensure proper temperature for killing Salmonellae