Lab 5 - Eggs, Egg Foams, & Foam Cakes Flashcards
Yolk
The yolk is held in place inside the egg by a twisted membranous structure called the chalazae and is surrounded by a thick white bugger called albumen aka “the whites”.
Albumen
The whites of the egg consist of 3 layers, the thick albumen sandwiched between two layers of thin albumen. Two membranes, inner and outer shell membranes, enclose the white and yolk.
Air cell (air pocket)
Formed at the large end of the egg between the thin and outer shell membranes as the warm freshly laid egg cools and contracts. It increases with age, cooling and moisture loss, and as a consequence of a large air cell size eggs will float.
Egg shell
A solid porous structure that permits passage of gases or microorganism a into and out of the shell. The egg’s natural protection is s thick sting called a “bloom” sealing the egg pores when it is laid.
Composition of the egg
13% protein and 11.5% fat, in addition to a small percentage of carbohydrate and ash.
2x as much white as yolk on a weight basis. White is 90% water and 10% protein.
Yolk contains 48% water and 16% protein and 32% fat. Half of the lipids in the yolk are triglyceride. Phospholipids, cholesterol and lipoproteins are also present in the yolk.
Thin albumen
Fluid egg white adjacent to the yolk and to the inner membrane
Thick albumen
Viscous white forming the middle layer of albumen
Bloom
Natural protective coating sealing the shell pores when an egg is laid
Ovalbumin
The most abundant protein in egg albumen; denatured readily by heat.
Salmonella enteritidis
Form of bacteria that can be incorporated into the yolk of an egg as the is forming the egg; potential source of food-borne illness if egg is not heated sufficiently during preparation.
Denaturation
Changes in confirmation of a protein (unfolding) caused by changes in temperature, acidic pH, or by surface hanged such as mechanical beating.
Coagulation
A process when denatured protein forms a solid mass. Eg. Gel
Baked custard
Sweetened milk and egg mixture that is baked without agitation until the egg protein coagulated and forms a gel.
Candling
Technique used to grade eggs in the shell. It is done in a darkened room with the egg held in front of a light. The light penetrates the egg makes it possible to observe the inside of the egg. This can determine the condition of the air cell, yolk, and white. It can also detect bloody white or blood spots, and it enables observation of germ development.
Changed due to age
During storage the bloom is lost resulting in increased porosity of the shell. Loss of moisture and carbon dioxide through the life of the shell causes the air cell to grow bigger. Loss of CO2 also causes a rise in the pH of the white from 7.6 to 9.6 which allows bacterial growth. As pH increases the thin membrane around the yolk becomes weaker and the older egg spreads more thinly over a large area and allows the yolk to move away from the center and towards the edge of the egg. This causes the yolk to be flatter and spread farther. Makes it more difficult to separate the white from the yolk without breaking the yolk. Older eggs also have more sulphur overtones.
Standards & grading of egg quality
Established by the Canada Department of agriculture. Described as egg relations of the Canadian agricultural products standard act (CAPS act). Based on interview and exterior appearance. Classified into A1, A,B, and C. Grade A1 will clean, sound shell, the you will be well centered and rounded, the air cell will be small, no abnormalities such as blood or meat spots. Within grade A1 and A there are jumbo, extra large, large, medium, small, and peewee.
Size, color of shell and color of yolk is not an indication of quality, household recipes are designed for large eggs. Egg color depends on the breed of the hen and yolk color depends on the feed given to the hen.
Storage
Fresh eggs store up to 5 weeks. Recommended to store in original egg cartons which protects eggs from off-flavors and odors, in an inside shelf and not the refrigerator door. If left in a dry area at room temperature they will drop grade within a week and become great environment for microbes. Eggs are washed cleaned and sanitized to prevent sanitation which are sufficient to rid surface pathogens but do nothing if yolks are contaminated.
Preservation
Liquid, frozen and dried whole egg, yolk and albumen are available. All commercial liquid, dry or frozen eggs products must be pasteurized 61C for 3.5 min. To destroy pathogens. Prior to drying to prevent the Maillard reaction in fire egg whites, the glucose in liquid eggs whites must be eliminated by bacterial or enzymatic fermentation. Frozen egg yolks become very viscous when they are frozen and thawed, to prevent this an anticoagulant of ten percent salt or sugar must be added to the yolk prior to freezing.
Functional properties
Coloring agents
Emulsifier
Thickening agents
Texturizing agents (incorporation of air)
Emulsifier agents
Lecithin and lysolscithin in egg yolk make excellent emulsifier agents. Mayonnaise
Egg whites coagulate at 65C, egg yolk at 70C.
Concentration of egg protein
Concentration of egg protein increases relative to other ingredients, the coagulation temperature is deceased; therefore, the time required for coagulation is lessened.
Kind of egg protein
When egg white is substituted for egg yolk he coagulation temperature is lowered. The cooking time is lessened.
Sugar
Elevates coagulation temperature of egg protein but it increases the tenderness of the custard.
Rate of heat penetration
Lowering the rate of heat penetration by lowering oven temperature and baking in water lowers coagulation temperature but lengthens cooking time.
pH of mixture
Protein coagulates most readily at heir isoelectric point. As the addition of acid brings the pH near the isoelectric point, the coagulation temperature is lowered and coagulation occurs faster.
Presence of salt
Coagulation temperature of egg protein mixtures is lowered by the addition of salt.
Green ring around yolk
Presence of ferrous sulphide
Foam
Gas in liquid dispersion. Foam stability is enhanced if
1. The surface tension is low
2. The vapour pressure is low
3. A substance (such as protein which denatures, carbohydrates, or fats) solidifies on the surface of the air pockets.
Egg whites meet all the above requirements.
Two most important factors in egg white foams
Stability and volume
Stability of foams
Influenced by degree of denaturation. Maximum stability there must be enough coagulation to produce a rigid film. However, as the air becomes more finely divided and the film of do from becomes thinner, it loses its elasticity and breaks. The greatest stability is found at the stiff peak stage. The stability of foam may be determined by amount of drainage lilt from a measured amount of foam over a specific time interval.
Volume of foam
Is influenced by temperature because surface tension is greater in cool whites than in white warmer to room temperature. The egg quality and freshness is also important. Thin whites (older eggs) form quickly but the volume is reduced upon extended holds its volume well.
Factors that influence foaming of egg white is:
Type of egg white and temperature
Type of egg whites
Egg white foams may be successfully prepared from egg white which have been frozen and thawed. Although reconfigured fried egg whites require a longer whipping time, stable foam may be obtained with this product.
Temperature
At low temperature liquids exhibit a higher surface tension. If he egg white is at refrigerator temperature, it will take longer time to form foam, and the volume and the stability will be less than that of egg whites beaten at room temperature.
