EGGS

PROPERTIES

Coagulation properties – trap milk when heated to form custardsProvide structure to foodsContribute to texture by influencing flavor, smoothness, moistness

NUTRITIVE VALUE

75% Water12% Protein10% Fat1% Carbohydrate1% minerals

LIPIDS

Almost all in yolkTriglyceride- almost all of eggs fat (66%)Phospholipids – lecithin (28%)Cholesterol – change in diet decreases amount of cholesterol (5%)Lecithin – naturally occurring emulsifierNegligible in albumen

PROTEINS

OVALBUMIN

Major protein in egg white – 54% of total solidsGlobular protein – easily denaturedContributes to structure of products

OVOTRANSFERRIN

12% of egg whiteComplexes with iron and inhibits growth of bacteria dependent on ironNot easily denatured by physical agitationVery susceptible to denaturation by heat when not bound by iron

OTHER PROTEINS

Ovomucoid – 11% of white solids, resistant to heat denaturation, inhibits proteolytic enzyme trypsinOvomucin – 3.5% of solids, foam stabilizer, involved in deterioration and thinning of egg white as it agesLysozyme – 3.4%, hydrolyze polysaccharides in walls of certain bacteria

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

CARBOHYDRATES

Very smallForm of glucose, mannose, galactoseGlucose and galactose react with proteins in Maillard reactionProduce undesirable brown discoloration in dried and cooked egg whites

VITAMINS AND MINERALS

Shell – mainly calciumYolk – phosphorus, iodine, zinc, iron (not well absorbed)Riboflavin – primarily in whiteYolk – Vitamin A (fat & carotenoid pigments)Vitamin D, folic acid, pantothenic acid and B12

PIGMENTS

Yolk – orange, red, yellow pigments – carotenoid pigments, found in yellow corn, green grass, alfalfaXanthophyll - comes from animal feed- not a precursor to vitamin AColorless sac, vitelline membrane surrounds yolkCHALAZAE - white cord to hold yolk in place

STRUCTURE - SHELL

Semi-permeable Porous - CO2 and H2O losses

Air cell - formed as two keratinlike membranes separateAntibacterial Color – breed of hen, no effect on nutritional quality

AGING CHANGES

Yolks enlarge, less viscous, flatten, no longer centeredWhites - thinnerContents shrink - H20 losses

pH changes from 7.6 9.6 - allows bacterial growth

INSPECTION

FDA and FSIS share responsibility for egg safety1999 egg safety plan to eliminate eggs as source of Salmonella enteridis2000 safe handling procedures on cartons

GRADING

Letter grades Nutritive value remains the sameShell - shape, texture, soundness, cleanlinessInterior - white, yolk, air cell sizeCandling - view of shell and inside of egg

INSPECTION

1970 Egg Products Inspection ActEstablished standardsInspects plants processing eggsWholesome and unadulterated and truthfully labeled egg productsImported eggs must meet same requirements as domestic

EGG SIZE

Not a part of qualitySize = weight per dozenYounger chickens lay smaller eggs3 ounces per dozen between each class1 egg = ~ 1/4 cup or 4 T

PROCESSING AND PRESERVATION

Mineral oil - same day laid, partially closes pores = less microorganism permeabilityegg holds more moisture retains more CO2 so resists pH

PASTEURIZATION

Destroys microorganismsRequired of all commercial liquid, dry or frozen productsMust maintain functional qualitiesUltrapasteurization with aseptic packaging - 10 week shelf life, Salmonella, listeria, E.coli freeNow pasteurized eggs in shell

FREEZING

Pasteurized prior to freezingUncooked retain propertiesCooked - syneresis when thawedYolks become gelatinous or lumpy when thawedRetard gelatination by adding salt, or sugar or corn syrup

DEHYDRATION

Began in 1870sWhites - remove glucose before drying (to prevent Maillard reaction), whipping aid is added to help with foamsAdd sugar to egg white to aid in hydrationYolks - irreversible changes in lipoproteins

STORAGE

Cold temperaturesHigh humidityHard cooked eggs - 1 weekWhites - 4 daysYolks - 1-2 daysWhole eggs in cartons, will absorb odors

PREPARATION PRINCIPLES

Centers around ability of proteins to coagulate when heatedCoagulation – protein molecules attract

and hold large quantities of water around themGel formation – Solid particles held suspended in a liquidWhites and yolks coagulate at different temperatures Whites at 144-1490F; yolks at 149-1590F

HEAT

Denatures, coagulates to form gelEgg white – transparent viscous masssoft, white, opaque gelHeat past 1580F white becomes tough, porousExcessively high temperatures egg white gel loses water, shrinks, toughensHigh temps yolks become crumbly in textureHeat too quickly coagulated proteins curdle

AGITATION

Denatures proteinsDisrupts bonds and initially causes foamingAs more air incorporated soft foam gets larger and stiffer because increased denaturationDenatured proteins eventually curdle separate into fluffy masses and become dry as liquid drains out

ACID

Lower coagulation temperatureToo much proteins denature severely and gel curdlespH greater than 9 or lower than 5 hardness and cohesiveness greaterProlonged heating peptidzation of protein and thinning of mixture (pie fillings become thin and runny)

SUGAR

Elevates temperature for coagulationThe more sugar the greater the heat needed for coagulationMore tender coagulum

SALT

Lowers temperature for coagulationCurdling may result from stirring gel so add salt before heating

STARCH

Coagulation and gelatinization occur at different temperaturesBring starch mixture to maximum thickness before adding uncooked egg

OTHER CONSIDERATIONS

DILUTION - coagulation temperature elevated if egg mixture is dilutedCONCENTRATION OF EGG – lowers coagulation temperature

COOKING CHANGES

Frying - coagulates protein, overheated pan overcoagulates egg toughHard cook - more tender if done at simmering not boiling temperatureColor - green with long and high heat exposure due to formation of ferrous sulfateOld eggs – ferrous sulfate may form due to increase in alkalinity

FOAMS

Created as whites are beaten to incorporate airHolds shape as protein coagulates around air cellsProvides leavening - dry foam not as effective as softYolks contain fat - physically interferes with alignment of protein around air cells

MERINGUES

Sweetened foamsWeeping - release of water from undercooked or undercoagulated whitesBeading - overcooked or overcoagulated meringues

FACTORS AFFECTING FOAMS

TEMPERTURE - room temperature best, but microbial growth a problempH - 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

FACTORS

SUGAR - less volume, add gradually at soft peak stage, after large cell and denaturation have begun; competes for waterFAT - Substantially less foaming, less volume; interfering agentLIQUID - Increases volume and tenderness of foam, increases chance of syneresis; decreases stability

FUNCTIONS

Binder – such as meat loaf, coatings, proteins coagulate binding food into cohesive massEmulsifier – form stable emulsions, coat oil drops to prevent them from combining with each otherFoaming, leavening agent – Air bubbles expand with heat and egg white film hardens

FUNCTIONS CONTINUED

Interfering agent – Prevent crystals from coming together and getting largerClarifying agent – proteins coagulate and trap loose particles

EGG SUBSTITUTES

NO yolks80% egg whitesCorn oil, nonfat milk solids, calcium caseinate, soy protein isolate, soybean oil, and other substances

NUTRITIVE VALUE

Biological value = 100- all absorbed protein is retained in the bodyProtein digestibility-correct amino acid score = measure of protein quality which compares amino acid balance with needs of a preschooler and corrects for digestibility = 1

SAFETY

Contents of freshly laid egg generally sterileSalmonella enteritidis - may be found insideEgg shell - surface high level of bacteria - may enter through poresFDA prohibits use of raw or lightly cooked eggs in food production or manufacturing facilities - must reach internal temperature of 1450F