Shell egg composition and processing
What vitamin is yolk a better source than any other natural food of animal origin other than liver?
Vitamin A
What can happen to the shell of an egg in a breaker plant?
Dry them and use for animal feed
- calcium and phosphorus content good for laying hens
2 causes for thinning of albumen;
1) Loss of carbohydrate group theory --> as eggs ages
- increase in free ovomucin
- increase in free carbohydrates
- carbohydrate chains (starch) degrade as pH increases
2)Lysozyme theory
- lysozyme decreases solubility with increasing pH
What protein helps lose attachment to shell membrane as pH increases?
Ovomucin
What is Meringue?
Foam + sugar
What are 3 albumen proteins?
- Ovalbumin (Foam formation)
- Ovotransferrin (Bacteriostatic, metal binding)
- Ovomucoid (bacteriostatic, inhibids protein digestion enzyme)
- Globulins (Foaming)
- Lysozyme (bactericidal, break cells)
- Ovomucin (Foam stability, albumen viscosity)
- Ovoflavoprotein (Bacteriostatic, binds riboflavin)
- Ovoinhibitor (Bacteriostatic)
- Avidin (Bacteriostatic, binds biotin)
What is a problem with pasteurization?
Potential for decreases functionality when heater (coagulated proteins)
1)Refrigeration (slows evaporation; <40F)
2)Oil Spray (seals pores to slow evaporation)
3)Increase relative humidity (creates equilibrium between egg and environment to decrease evaporation of water from egg pores)
4)Increase CO2 environment (MAP - modified atmosphere packaging) (can cause cloudy whites)
5)Good inventory control
What is the 'green' coloring in hard cooked eggs and what can affect it?
Iron, Fe (in yolk) + Sulfur, S (in albumen) --> Iron Sulfide, FeS (black precipitate)
- Cooking techniques and age of eggs can affect greening
What are Humectant?
Humectants are hygroscopic ('water-pulling') substances that are incorporated in food to promote retention of moisture and include moisture-retention agents and anti-dusting agents.
- useful function for bread
Why is yolk lipid composition responsive to diet?
Because yolk is a lipid which is absorbed through the intestine and deposited in the yolk.
-Spray drying (most common)
-Tray drying
-Membrane Filtration
-Storage
Exterior Quality Measurements (3);
1)Specific Gravity (density of egg vs. density of solution)
- correlated to shell thickness (in fresh eggs only)
- non-destructive measurement
2)Egg shell thickness
- direct measurements of shell thickness
- destructive measurement
- need at least 0.33 mm to have a greater than 50% chance of moving through the normal processing scheme
3)Egg Shell Strength
- measures force used to crack shell
- destructive
What are 5 factors affecting coagulation?
1)Temperature
- rate of coagulation increases with temperature
- high temperatures lead to gels that are too firm
2)Salt
- Speed up coagulation
3)Sugar
- increases egg albumen coagulation temperature
- decreases rate of coagulation produces soft gels
4)Acids
- Prevents over coagulation in egg white foams
- Lowers coagulation temperature of whole egg; speeds up coagulation
5)Alkali
- Translucent gels formed at high pH
6) Time
- Slower coagulation at lower temperatures
- Fast coagulation at high temperatures
7)pH
- higher pH whites/yolks (stored eggs) produce low gel strengths with lower water holding capacity
8)Adding ingredients
- can prevent curdling and syneresis
9)Adding liquids
- Dilutes proteins, increasing coagulation temperature
- Softer gels and slow thickening
What are 5 factors affecting foaming?
1) egg age (fresh eggs - good ability and stability) (old eggs - good ability and poor stability (watery, thin egg white))
2) Egg pH (high pH leads to poor protein functionality; lowers foam stability)
3)Solids content (increases solid increases foam volume and stability) (older hens - lower solids content; poor stability)
4)Yolk/fat (decreases foam ability) (decreases foam stability by forming yolk-ovomucin complex)
5)Mechanical Action (beating, chopping-denatures protein, over beating can destroy foams one they are formed)
6)Pasteurization (increases whip time)
7)Temperature during foam formation (Decreases whip time at room temperature but too much heat generated early during foam formation can weaken foams)
8)Temperature during cooking (Protein denaturation, set final structure by protein coagulation too much can decrease foam volume)
9)Water (increases initial volume, but decreases stability because of decreases solids)
10)Acids (decrease pH, increase protein denaturation, acid initial foaming)
11)salt (help to unwind proteins during initial foaming; increases protein solubility)
12)Sugar (delays initial foam formation, increases foam viscosity aiding in stabilization and used with dried egg whites to increase dried egg white solubility)
13)copper (binds conalbumin helps to make it more heat stable and copper bowls used for making foams)
14)Flour/sugar (in cakes) (help to stabilize structure and give texture)
15)Gums (stabilize foams, help to prevent moisture loss)
16) Citric acid/cream of tartar (improves egg white protein functionality by reducing pH and stabilizes product color)
17)Surfactants (ease of foaming and Sodium Lauryl Sulfate (SLS) added to dried egg whites to enhance foaming, reduces surface tension)
18)Esters (ease of foaming, and Triethyl Citrate added to high whip liquid egg white to aid in foaming, reduces surface tension)
What has been found to help prevent macular degeneration in the elderly?
Lutein and Zeaxanthin
What happens when a mixture (icecream) with yolk added is frozen slowly?
During slow freezing, the ice crystals break the protein coat (breaks emulsion)
Interior Quality measurements (destructive)(3) - (non-destructive)(1);
Destructive -
1) Haugh Units (albumen)
- mathematical relationship between thick albumen height and egg weight
- directly related to egg weight thinning
2) Yolk Index
- ratio of yolk height to average yolk diameter
3) pH - pH 7.4(initial) --> pH 10(alkaline)(final)
Non-Destructive
1) Candling
- air cell size
- Yolk mobility
With egg white being the major foaming protein used in the food industry, which of the proteins in egg whites are used for ability and which is used for stability?
Foam ability - ovalbumin
Foam stability - ovomucin
For breads what are some functional rationales that the egg can have;
-browning qualities
-Structural desirability
-egg white imparts crisper crust to hard rolls and hearth rolls
-adds flavor benefits
-adheres seeds and grains to the outside of bread
-adds color to egg breads and varieties
-adds nutritional benefits
What are the 3 things that the USDA quality grading of shell eggs shorted for?
1) based on size or weight and quality factors of the shell (exterior grading)
2) internal components (yolk, egg white, air cell)
3) presence of abnormalities (interior grading)
What are problems when spray drying?
1)Albumen turns pink because of Fe bound to conalbumin
2)browning -- protein + sugars with heat (Maillard reaction)
Types of Spoilage;
- Black Rot; Aeromonus/Proteus; HS production
- Red Rot; Serratia; pigments
- Green or Pink Rot; Pseudomonas; HS, pigments
- "Taint" - organisms in large numbers
What is the role of emulsifiers in emulsions?
and
Primary emulsifiers from egg yolk?
Role:
-Formation of emulsion
- droplets that form are smaller
-Stabilization of emulsion
- reduce the coalescence of droplets
Egg Yolk:
-phospholipids - Lecithin
-Lipoproteins
- Egg whites can slow down sugar crystallization in confectioneries resulting in many fine crystals
- in ice creams, eggs control water-molecule crystallization, encouraging small ice crystals, resulting in smooth and creamy product