Value-added eggs Health of Consumer Special Attributes Nutrient Content of Feed Conditions Under Which Hens Raised Lower-Cholesterol Eggs Omega-3 Fatty Acids Vitamin E Levels Animal Friendly Practices
Eggs parts Yolk Germinal Disc Vitelline Membrane Albumen Egg White Chalaza pl. Chalazae Shell Membranes Inner Outer Air Cell Between 2 Shell Membranes Shell Cuticle or Bloom
Eggs Components Chalaza pl. Chalazae Ropy Twisted Strands Of Albumen Anchor Yolk to Center of Thick Egg White Vitelline Membrane Membrane Surrounding Egg Yolk Attached to Chalazae Cuticle or Bloom Waxy Coating on Eggshell Protects Against Bacterial Contamination & Moisture Loss
Egg parts zShell: 9-12% of total egg weight. Made of calcium carbonate and magnesium carbonate deposited on protein network. zEgg whites or albumen: about 60% of total egg weight. Contains over 40 proteins. zYolk: 30-33% of total egg weight. The only egg part containing fat and cholesterol.
Chemical (proximate) composition of egg components
Eggs micronutrients Vitamins Fat-SolubleA D E K B 2 B 12 Folate Biotin Pantothenic Acid Minerals Selenium Iodine Zinc Iron Copper Iron Not Bioavailable Iron & Sulfur React in Overcooked Eggs > Strong Off-Odor
Egg safety zRemember -egg may cause illness known as salmonellosis. This may result from contamination on the outside of the shell as well as infection inside the egg itself. zAny egg that is cracked when purchased or that cracked during preparation should be discarded. zEggs should not be stored at room temperature for more than two hours. zHard cooked eggs should be kept cool until serving
Egg safety zSeparating the yolk from albumen after the shell is broken in half by passing it back and forth between the halves should be avoided. zEggs should be thoroughly cooked for those at risk for infections: the elderly, infants, young children or the ill.
Uses of eggs in food preparation zBinding and coating zLeavening zEmulsifying agent zInterfering agent zClarifying agent
Changes in the egg quality zOccurs as soon as egg is laid zAre affected by the conditions the egg is held. zFirst change - loss of weight zFormation of the air cell on blunt side of egg - due to contraction of egg content. zEgg becomes more alkaline due to loss of carbon dioxide. zpH of albumen rises from 7.6 to zpH of yolk rises from to 6.8
Eggs storage Size of An Eggs Air Cell Provides Another Indication of Its Age
Grading of eggs involves zassessment of interior and exterior quality zcondition of albumen and yolk zsize of air cell zsoundness of egg shell zweight zcleanness of egg
Eggs grading Haugh Units Freshness of An Egg Detected By Cracking It Open Onto A Flat Surface & Looking At Height of Thick Albumen Fresh Egg Whites Sit Up Tall & Firm Older Ones - Spread Out
Egg Sizes by weight
Proteins zOvalbumin - 54%; globular protein that readily denatures. zOvotransferrin (Conalbumin) - 12%; it forms complexes with iron. The most heat sensitive if not bound to metal ion. zOvomucoid - 11%; resistant to heat denaturation; trypsin inhibitor. zLysozyme - 3.4%; enzyme that hydrolyses polysaccharides present in the cell wall of certain bacteria. zAvidin - 0.5%; it forms complex with biotin. Vitamin antagonist. Biotin deficiency is produced after consumption of 24 raw eggs per day. zVitellin and lipovitellins - proteins found in yolk -excellent emulsifying agents.
Egg proteins cont.
Coagulation of egg proteins zAlbumen: coagulation starts at 62 C, mass fully coagulates at 65 C. At 70 C coagulum is firm. zYolk: coagulation starts at 65 C; mass fully coagulates at 70 C. Beaten eggs coagulate at slightly higher temperature ~ 69 C.
Thickening/coagulation of egg mixture depends on: zRate of heating - egg proteins tend to curdle when heated too quickly. zHeating time and heating past coagulation - causes albumen protein to lose water, shrink and toughen, while egg yolk becomesmore crumbly due to fat content. zAddition of sugar -elevates the coagulation temperature and produces more tender coagulum. zAddition of salt - lowers the coagulation temperature zAddition of acid - lowers the coagulation temperature - too much acid will curdle the proteins. zAddition of starch - the coagulation temperature of egg proteins and gelatinization temperature of starch are different. Best results are obtained by adding uncooked egg to gelatinized starch. zAddition of water - elevates the coagulation temperature.
Eggs preparation Microwaving Eggs Cook Extremely Rapidly Special Caution Taken to Avoid Overcooking Manufacturers Instructions Should Be Followed for Microwave Egg Cooking Whole Eggs w/ Intact Shells Never Microwaved!! Steam Expanding Within Shell Can Cause Eggs to Burst Same Principle Applies to Whole Eggs Out of the Shell Puncture Egg Yolks w/ Toothpick or Tip of a Knife Prior to Microwaving
Eggs preparation Custards Ingredients Milk &/or Cream Sweeteners Sugar Honey Flavorings Vanilla Nutmeg Etc. Eggs or Egg Yolks Sweet or Savory Preparation Stirred or Baked Sweet Custards Puddings or As Fillings Savory Custards Nonsweet Quiches Stirred Custard Soft Custard or Custard Sauce Ingredients Stirred While Heated Baked Custard Poured Into Ungreased Custard Cups Placed In The Oven
Eggs storage Restaurants Food Service Institutions Other Food Manufacturers Must Be Especially Careful About Storing Eggs Because Large Quantities are Purchased Storage Eggs Used w/i 1 Mo Stored Up to 6 Mos. Eggs Treated w/ A Light Coat of Oil or Plastic Stored In High Humidity At Low Refrigerator Temperatures Very Close to Eggs Freezing Point 29°-32°F –1.5°-0°C
Preservation of eggs zREFRIGERATION: zStorage under modified atmosphere (humidity, carbon dioxide) zDipping in mineral oil zThermostabilization - dipping for a short time in hot liquid.
Eggs preservation Freezing Cannot Freeze Whole Egg It Will Crack Under the Expanding Liquids Food Manufacturers Break the Eggs Open At the Processing Plants Where Contents Are Frozen WholeWhites & Yolk Mixed Separated As Whites or Yolks
Preservation of eggs zFREEZING cont. : zAlbumen can be frozen without addition of any protectants. zYolk -without addition of protectant will form irreversible gel. Therefore glycerin, salt or sugar are added to prevent gelation zCooked eggs can be frozen by any method.
Preservation of eggs by drying zEgg can be dried by spray drying. Free flowing of powder is achieved by addition of silicoaluminum or silicone dioxide. zGlucose present in egg affect lower solubility, affect the flavor and color (Maillard reaction) zGlucose is removed by oxidation to glucuronic acid in the presence of glucose oxidase. zHydrogen peroxide formed in this reaction is removed by catalase.
Preservation of eggs by drying Dried Drying Eggs Is a Simple Process Whole Eggs or Separated Yolks Are Spray-Dried Create a Fine Powder Which Is Mixed w/ Anti-Caking Substances to Prevent Clumping Egg Whites Granule, Flake, or Milled Textures Stored Up to 1 Year In Refrigerator Kept In Tightly Closed Containers to Prevent Clumping That Can Result from Moisture Accumulation
Food foams zFoam is a gas (air) dispersed in liquid. zFoam is stabilized by surface acting agent referred to as foaming agent (example protein that forms a film coat arround air bubble. Hydrophobic groups are directed towards air, while hydrophilic towards water. zEgg foams (meringues, angel cakes, sponge cakes, souffles, fluffy omelets) zMilk foams
Egg foams Factors Affecting Foaming Beating Technique Start Slow Gradually Increasing Speed Testing for Doneness Observe Peak Formation Avoid Overwhipping Prevent Collapse & Separation of Foam Temperature Bowl Beaters Eggs Room Temperature
Quality of egg foam is affected by: zSugar zAcids zSalt zFat zTemperature zEquipment used
Egg foams Factors Affecting Foaming Bowl Deep Bowl Rounded Bottom Sloping Sides Avoid Plastic Bowls Separation of Eggs Egg Yolk Contains Fat Interferes w/ Foam Egg Separators Careful Separation of Egg White from Yolk Imperative Do Not Pass Egg Back & Forth Between Two Shell Halves