EGGS

1. EGGS

2. PROPERTIES • Coagulation properties – trap milk when heated to form custards • Providestructure to foods • Contribute totexture by influencing flavor, smoothness, moistness

3. NUTRITIVE VALUE • 75% Water • 12% Protein • 10% Fat • 1% Carbohydrate • 1% minerals

4. LIPIDS • Almost all in yolk • Triglyceride- almost all of eggs fat (66%) • Phospholipids – lecithin (28%) • Cholesterol – change in diet decreases amount of cholesterol (5%) • Lecithin – naturally occurring emulsifier • Negligible in albumen

5. PROTEINS

6. OVALBUMIN • Major protein in egg white – 54% of total solids • Globular protein – easily denatured • Contributes to structure of products

7. OVOTRANSFERRIN • 12% of egg white • Complexes with iron and inhibits growth of bacteria dependent on iron • Not easily denatured by physical agitation • Very susceptible to denaturation by heat when not bound by iron

8. OTHER PROTEINS • Ovomucoid – 11% of white solids, resistant to heat denaturation, inhibits proteolytic enzyme trypsin • Ovomucin– 3.5% of solids, foam stabilizer, involved in deterioration and thinning of egg white as it ages • Lysozyme– 3.4%, hydrolyze polysaccharides in walls of certain bacteria

9. OTHER PROTEINS • Avidin– minute amounts Presence has nutritional significance In natural state, binds with biotin – biotin cannot be absorbed Heating inactivates • Vitellin and Lipovitellinin – lipoproteins that function as emulsifying agents, surrounds yolk

10. CARBOHYDRATES • Very small • Form of glucose, mannose, galactose • Glucose and galactose react with proteins in Maillard reaction • Produce undesirable brown discoloration in dried and cooked egg whites

11. VITAMINS AND MINERALS • Shell – mainly calcium • Yolk – phosphorus, iodine, zinc, iron (not well absorbed) • Riboflavin – primarily in white • Yolk – Vitamin A (fat & carotenoid pigments) • Vitamin D, folic acid, pantothenic acid and B12

12. PIGMENTS • Yolk – orange, red, yellow pigments – carotenoid pigments, found in yellow corn, green grass, alfalfa • Xanthophyll - comes from animal feed- not a precursor to vitamin A • Colorless sac, vitelline membrane surrounds yolk • CHALAZAE - white cord to hold yolk in place

13. STRUCTURE - SHELL • Semi-permeable • Porous - CO2 and H2O losses • Air cell - formed as two keratinlike membranes separate • Antibacterial • Color – breed of hen, no effect on nutritional quality

14. AGING CHANGES • Yolks enlarge, less viscous, flatten, no longer centered • Whites - thinner • Contents shrink - H20 losses • pH changes from 7.6 9.6 - allows bacterial growth

15. INSPECTION • FDA and FSIS share responsibility for egg safety • 1999 egg safety plan to eliminate eggs as source of Salmonella enteridis • 2000 safe handling procedures on cartons

16. GRADING • Letter grades • Nutritive value remains the same • Shell - shape, texture, soundness, cleanliness • Interior - white, yolk, air cell size • Candling - view of shell and inside of egg

17. INSPECTION • 1970 Egg Products Inspection Act • Established standards • Inspects plants processing eggs • Wholesome and unadulterated and truthfully labeled egg products • Imported eggs must meet same requirements as domestic

18. EGG SIZE • Not a part of quality • Size = weight per dozen • Younger chickens lay smaller eggs • 3 ounces per dozen between each class • 1 egg = ~ 1/4 cup or 4 T

19. PROCESSING AND PRESERVATION • Mineral oil - same day laid, partially closes pores = less microorganism permeability • egg holds more moisture retains more CO2 so resists pH

20. PASTEURIZATION • Destroys microorganisms • Requiredof all commercial liquid, dry or frozen products • Must maintain functional qualities • Ultrapasteurization with aseptic packaging - 10 week shelf life, • Salmonella, listeria, E.coli free • Now pasteurized eggs in shell

21. FREEZING • Pasteurized prior to freezing • Uncooked retain properties • Cooked - syneresis when thawed • Yolks become gelatinous or lumpy when thawed • Retard gelatination by adding salt, or sugar or corn syrup

22. DEHYDRATION • Began in 1870s • Whites - remove glucose before drying (to prevent Maillard reaction), whipping aid is added to help with foams • Add sugar to egg white to aid in hydration • Yolks - irreversible changes in lipoproteins

23. STORAGE • Cold temperatures • High humidity • Hard cooked eggs - 1 week • Whites - 4 days • Yolks - 1-2 days • Whole eggs in cartons, will absorb odors

24. PREPARATION PRINCIPLES • Centers around ability of proteins to coagulate when heated • Coagulation – protein molecules attract and hold large quantities of water around them • Gel formation – Solid particles held suspended in a liquid • Whites and yolks coagulate at different temperatures • Whites at 144-1490F; yolks at 149-1590F

25. HEAT • Denatures, coagulates to form gel • Egg white – transparent viscous masssoft, white, opaque gel • Heat past 1580F white becomes tough, porous • Excessively high temperatures egg white gel loses water, shrinks, toughens • High temps yolks become crumbly in texture • Heat too quickly coagulated proteins curdle

26. AGITATION • Denatures proteins • Disrupts bonds and initially causes foaming • As more air incorporated  soft foam gets larger and stiffer because increased denaturation • Denatured proteins eventually curdle separate into fluffy masses and become dry as liquid drains out

27. ACID • Lower coagulation temperature • Too much  proteins denature severely and gel curdles • pH greater than 9 or lower than 5  hardness and cohesiveness greater • Prolonged heating  peptidzation of protein and thinning of mixture (pie fillings become thin and runny)

28. SUGAR • Elevates temperature for coagulation • The more sugar the greater the heat needed for coagulation • More tender coagulum

29. SALT • Lowers temperature for coagulation • Curdling may result from stirring gel so add salt before heating

30. STARCH • Coagulation and gelatinization occur at different temperatures • Bring starch mixture to maximum thickness before adding uncooked egg

31. OTHER CONSIDERATIONS • DILUTION - coagulation temperature elevated if egg mixture is diluted • CONCENTRATION OF EGG – lowers coagulation temperature

32. COOKING CHANGES • Frying - coagulates protein, overheated pan overcoagulates egg  tough • Hard cook - more tender if done at simmering not boiling temperature • Color - green with long and high heat exposure due to formation of ferrous sulfate • Old eggs – ferrous sulfate may form due to increase in alkalinity

33. FOAMS • Created as whites are beaten to incorporate air • Holds shape as protein coagulates around air cells • Provides leavening - dry foam not as effective as soft • Yolks contain fat - physically interferes with alignment of protein around air cells

34. MERINGUES • Sweetened foams • Weeping - release of water from undercooked or undercoagulated whites • Beading - overcooked or overcoagulated meringues

35. FACTORS AFFECTING FOAMS • TEMPERTURE - room temperature best, but microbial growth a problem • pH - ACID - beginning of beating = less volume, more stability, should be added after eggs reached foamy stage and have large air cells; (cream of tartar) • SALT - adds flavor, less volume, less stability, add after foamy stage

36. FACTORS • SUGAR - less volume, add gradually at soft peak stage, after large cell and denaturation have begun; competes for water • FAT - Substantially less foaming, less volume; interfering agent • LIQUID - Increases volume and tenderness of foam, increases chance of syneresis; decreases stability

37. FUNCTIONS • Binder – such as meat loaf, coatings, proteins coagulate binding food into cohesive mass • Emulsifier – form stable emulsions, coat oil drops to prevent them from combining with each other • Foaming, leavening agent – Air bubbles expand with heat and egg white film hardens

38. FUNCTIONS CONTINUED • Interfering agent – Prevent crystals from coming together and getting larger • Clarifying agent – proteins coagulate and trap loose particles

39. EGG SUBSTITUTES • NO yolks • 80% egg whites • Corn oil, nonfat milk solids, calcium caseinate, soy protein isolate, soybean oil, and other substances

40. NUTRITIVE VALUE • Biological value = 100- all absorbed protein is retained in the body • Protein digestibility-correct amino acid score = measure of protein quality which compares amino acid balance with needs of a preschooler and corrects for digestibility = 1

41. SAFETY • Contents of freshly laid egg generally sterile • Salmonella enteritidis - may be found inside • Egg shell - surface high level of bacteria - may enter through pores • FDA prohibits use of raw or lightly cooked eggs in food production or manufacturing facilities - must reach internal temperature of 1450F