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Eggs

Chapter 11

Foods containing eggs

Eggs types

Chicken eggs Standard Fertile Free-range Organic

Non-chicken eggs Duck Goose Ostrich Quail Turkey

Value-added eggs

Health of Consumer Special Attributes

Nutrient Content of FeedConditions Under Which Hens Raised

Lower-Cholesterol Eggs Omega-3 Fatty Acids Vitamin E Levels Animal Friendly Practices

Eggs parts

YolkGerminal Disc Vitelline Membrane

Albumen Egg WhiteChalaza pl. Chalazae

Shell MembranesInner Outer

Air Cell Between 2 Shell Membranes Shell

Cuticle or Bloom

Eggs Components

Chalaza pl. ChalazaeRopy Twisted Strands Of Albumen Anchor Yolk to Center of Thick Egg White

Vitelline MembraneMembrane Surrounding Egg Yolk Attached to Chalazae

Cuticle or BloomWaxy Coating on Eggshell Protects Against

Bacterial Contamination & Moisture Loss

EGGS

Egg parts

Shell: 9-12% of total egg weight. Made of calcium carbonate and magnesium carbonate deposited on protein network.

Egg whites or albumen: about 60% of total egg weight. Contains over 40 proteins.

Yolk: 30-33% of total egg weight. The only egg part containing fat and cholesterol.

Chemical (proximate) composition of egg components

Compo- nent

Water[%]

Protein[%]

Lipid[%]

Carbohy-drates

[%]

Ash [%]

Albumen 87.6 9.7-10.6 0.03 0.4-0.9 0.5-0.6

Yolk 51.1 15.7-16.6 31.8-35.5 0.2-1.0 1.1

Whole egg 73.7 12.8-13.4 10.5-11.8 0.3-1.0 0.8-1.0

Eggs micronutrients

Vitamins Fat-Soluble A D E KB2 B12 Folate Biotin Pantothenic Acid

Minerals Selenium Iodine Zinc Iron Copper Iron Not Bioavailable Iron & Sulfur React in Overcooked Eggs―> Strong Off-Odor

Egg safety

Remember -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.

Any egg that is cracked when purchased or that cracked during preparation should be discarded.

Eggs should not be stored at room temperature for more than two hours.

Hard cooked eggs should be kept cool until serving

Egg safety

Separating the yolk from albumen after the shell is broken in half by passing it back and forth between the halves should be avoided.

Eggs should be thoroughly cooked for those at risk for infections: the elderly, infants, young children or the ill.

Uses of eggs in food preparation

Binding and coating

Leavening

Emulsifying agent

Interfering agent

Clarifying agent

Changes in the egg quality

Occurs as soon as egg is laid Are affected by the conditions the egg is held. First change - loss of weight Formation of the air cell on blunt side of egg -

due to contraction of egg content. Egg becomes more alkaline due to loss of carbon

dioxide. pH of albumen rises from 7.6 to 8.9-9.4 pH of yolk rises from 5.9-6.1 to 6.8

Eggs storage

Size of An Egg’s Air Cell Provides Another Indication of Its Age

Grading of eggs involves

assessment of interior and exterior quality

condition of albumen and yolksize of air cellsoundness of egg shellweightcleanness 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

Egg Candling

Proteins

Ovalbumin - 54%; globular protein that readily denatures. Ovotransferrin (Conalbumin) - 12%; it forms complexes

with iron. The most heat sensitive if not bound to metal ion. Ovomucoid - 11%; resistant to heat denaturation; trypsin

inhibitor. Lysozyme - 3.4%; enzyme that hydrolyses

polysaccharides present in the cell wall of certain bacteria. Avidin - 0.5%; it forms complex with biotin. Vitamin

antagonist. Biotin deficiency is produced after consumption of 24 raw eggs per day.

Vitellin and lipovitellins - proteins found in yolk -excellent emulsifying agents.

Egg proteins cont.

Coagulation of egg proteins

Albumen: coagulation starts at 62 C, mass fully coagulates at 65 C. At 70 C coagulum is firm.

Yolk: 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:

Rate of heating - egg proteins tend to curdle when heated too quickly.

Heating time and heating past coagulation - causes albumen protein to lose water, shrink and toughen, while egg yolk becomesmore crumbly due to fat content.

Addition of sugar -elevates the coagulation temperature and produces more tender coagulum.

Addition of salt - lowers the coagulation temperature Addition of acid - lowers the coagulation temperature - too much

acid will curdle the proteins. Addition 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.

Addition of water - elevates the coagulation temperature.

Eggs preparation

Microwaving Eggs Cook Extremely

Rapidly Special Caution Taken

to Avoid Overcooking Manufacturer’s

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 CreamSweeteners Sugar HoneyFlavorings Vanilla Nutmeg Etc. Eggs or Egg Yolks

Sweet or SavoryPreparation

Stirred or Baked

Sweet Custards Puddings or As Fillings

Savory CustardsNonsweet 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

RestaurantsFood Service

InstitutionsOther 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 Egg’s Freezing Point 29°-32°F –1.5°-0°C

Preservation of eggs

REFRIGERATION:Storage under modified atmosphere

(humidity, carbon dioxide)Dipping in mineral oilThermostabilization - 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 FrozenWhole Whites & Yolk MixedSeparated As Whites or Yolks

Preservation of eggs

FREEZING cont. :Albumen can be frozen without addition of

any protectants.Yolk -without addition of protectant will

form irreversible gel. Therefore glycerin, salt or sugar are added to prevent gelation

Cooked eggs can be frozen by any method.

Preservation of eggs by drying

Egg can be dried by spray drying. Free flowing of powder is achieved by addition of silicoaluminum or silicone dioxide.

Glucose present in egg affect lower solubility, affect the flavor and color (Maillard reaction)

Glucose is removed by oxidation to glucuronic acid in the presence of glucose oxidase.

Hydrogen 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 PowderWhich 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

Foam is a gas (air) dispersed in liquid.

Foam 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.

Egg foams (meringues, angel cakes, sponge cakes, souffles, fluffy omelets)

Milk 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

EGGSFUNCTIONS

Quality of egg foam is affected by:

SugarAcidsSaltFatTemperatureEquipment used

Egg foams

Factors Affecting Foaming Bowl

Deep Bowl Rounded Bottom Sloping SidesAvoid Plastic Bowls

Separation of EggsEgg Yolk Contains Fat Interferes w/ FoamEgg Separators

Careful Separation of Egg White from Yolk Imperative Do Not Pass Egg Back & Forth Between Two Shell

Halves

Egg substitutes

Better’n EggEgg BeatersScramblersSecond NatureSimply Eggs