Lab 5 - Eggs, Egg Foams, & Foam Cakes

Question 1

Yolk

Answer 1

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”.

Question 2

Albumen

Answer 2

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.

Question 3

Air cell (air pocket)

Answer 3

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.

Question 4

Egg shell

Answer 4

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.

Question 5

Composition of the egg

Answer 5

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.

Question 6

Thin albumen

Answer 6

Fluid egg white adjacent to the yolk and to the inner membrane

Question 7

Thick albumen

Answer 7

Viscous white forming the middle layer of albumen

Question 8

Bloom

Answer 8

Natural protective coating sealing the shell pores when an egg is laid

Question 9

Ovalbumin

Answer 9

The most abundant protein in egg albumen; denatured readily by heat.

Question 10

Salmonella enteritidis

Answer 10

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.

Question 11

Denaturation

Answer 11

Changes in confirmation of a protein (unfolding) caused by changes in temperature, acidic pH, or by surface hanged such as mechanical beating.

Question 12

Coagulation

Answer 12

A process when denatured protein forms a solid mass. Eg. Gel

Question 13

Baked custard

Answer 13

Sweetened milk and egg mixture that is baked without agitation until the egg protein coagulated and forms a gel.

Question 14

Candling

Answer 14

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.

Question 15

Changed due to age

Answer 15

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.

Question 16

Standards & grading of egg quality

Answer 16

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.

Question 17

Storage

Answer 17

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.

Question 18

Preservation

Answer 18

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.

Question 19

Functional properties

Answer 19

Coloring agents
Emulsifier
Thickening agents
Texturizing agents (incorporation of air)

Question 20

Emulsifier agents

Answer 20

Lecithin and lysolscithin in egg yolk make excellent emulsifier agents. Mayonnaise

Egg whites coagulate at 65C, egg yolk at 70C.

Question 21

Concentration of egg protein

Answer 21

Concentration of egg protein increases relative to other ingredients, the coagulation temperature is deceased; therefore, the time required for coagulation is lessened.

Question 22

Kind of egg protein

Answer 22

When egg white is substituted for egg yolk he coagulation temperature is lowered. The cooking time is lessened.

Question 23

Sugar

Answer 23

Elevates coagulation temperature of egg protein but it increases the tenderness of the custard.

Question 24

Rate of heat penetration

Answer 24

Lowering the rate of heat penetration by lowering oven temperature and baking in water lowers coagulation temperature but lengthens cooking time.

Question 25

pH of mixture

Answer 25

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.

Question 26

Presence of salt

Answer 26

Coagulation temperature of egg protein mixtures is lowered by the addition of salt.

Question 27

Green ring around yolk

Answer 27

Presence of ferrous sulphide

Question 28

Foam

Answer 28

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.

Question 29

Two most important factors in egg white foams

Answer 29

Stability and volume

Question 30

Stability of foams

Answer 30

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.

Question 31

Volume of foam

Answer 31

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.

Question 32

Factors that influence foaming of egg white is:

Answer 32

Type of egg white and temperature

Question 33

Type of egg whites

Answer 33

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.

Question 34

Temperature

Answer 34

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.