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
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