EGGS

Egg• One of nature's most complete foods

• Contains high quality protein with all of the essential amino acids

• Contains all of the essential vitamins except vitamin C

• Contains most of the essential minerals

Egg• Egg products are particularly good for

fortifying low quality protein foods

• Biologically, except, eggs is the best source of balanced natural protein

• Egg protein is frequently used as a reference standard of 100 to compare the biological values of other proteins

Egg• One Large egg has approximately 5 grams

of fat

• Monounsaturated and polyunsaturated fatty acids account for about 70% of the total fatty acids

• Only 30% of the fatty acids are saturated

• Breed of hen • Age• Diseases and other disorders • Light • Feeding • Quality of feed • Temperature • Humidity • The laying house • Handling • Processing

Factors that Influence Egg Quality

Egg Processing

• Up to 1 week at 13 oC• More than 1 week, 7 oC

Egg Holding

Egg Processing • Salmonella Enteritidis could survive in

the reproductive tract of the hen

• In rare instances (1 in 20,000) this bacterium can be deposited inside the egg in the egg white

• Number of bacteria/egg is very low (because the egg white discourages bacterial growth)

Egg ProcessingThe bacteria grows

• Once the shell is cracked and the iron-rich yolk is mixed with the white

• If the yolk membrane deteriorates (depends on the storage time and temperatures) bacteria can grow inside the intact egg

• Salmonella poisoning from eggs is increasing in Australia

Egg Processing• Initially, an egg contains about 30 ml of

dissolved carbon dioxide(CO2), all in the white

• Egg white is one of a few alkaline food products

• The pH of egg white is about 8.2• As the egg ages and loses carbon

dioxide through the shell, the pH increases to about 9.4

• The whole egg pH range from 7.0 - 7.6

Egg Processing

• Edible interior quality eggs should be used• Shell must be sound and free from adhering

dirt and foreign materials• Type of egg can affect the yield, yolk colour,

and microbial content

Egg Breaking

Egg Breaking

Egg Processing

Whole egg products: Min 3.5 min at 35 oC

Pasteurisation

Egg Processing

• Functional properties : Decrease whipping ability

• Nutritional quality: Vitamin, amino acids

• Microbial content• Physical properties

Effects of Heating on Egg Products

Egg Processing

• Removal of sugar from egg product

• Dehydrated egg products are subjected to decrease in functionality, off colour and flavour development during storage

• Mallard Browning: Reducing sugar and amino acid

Desugarisation of Egg Products

Egg Processing

• Dried egg whites• Dried plain whole egg and yolk• Blends• Specialty dried egg products

Types of Dried Egg Products

• Spray dried, whipping type: Usually have a whipping aid such as sodium lauryl sulphate. Angel food cake

• Spray dried, non-whipping type: Coagulation is more important than whipping. Layer-typecakes

• Pan dried: Available in flakes, granules and powder forms

• Instant dissolving

Dried Egg Products - Dried Egg Whites

Dried Egg Products - Dried Egg Whites

• Standard whole eggs• Standard egg yolk• Glucose free whole eggs• Glucose free egg yolk• Free-flowing whole eggs• Free-flowing egg yolk

• Free-flowing agents: Silicon dioxide (< 1%)

Dried Egg Products - Dried plain whole egg and yolk

Dried Egg ProductsDried Egg Yolk

• Whole egg + sucrose• Whole egg + corn syrup• Whole egg + yolk + corn syrup• Egg yolk + corn syrup

Dried Egg Products - Dry blends

• Whole egg - 50%• Skim milk - 30%• Vegetable oil - 15%• Salt ~ 1.5%

Dried Egg Products - Specialty dried egg products

Dried Scrambled Egg Mix

Imitation Whole Eggs

Egg white and substituted ingredients for yolk

Dried Egg Products - Specialty dried egg products

• Soy protein• Shortening• Emulsifiers

Eggs with other functional Ingredients

Egg Processing• Liquid egg whites

• Solid content ~12%• pH 8.4 - 9.2

• Liquid egg yolk• Solid content 46 - 48%• pH ~ 6.0

• Liquid whole eggs• Solid content 23 - 25%• pH 7.0 - 7.6

Natural Egg Products

Egg Processing

Egg shells• Fertilizer• Feed and waste

product

Inedible egg products• Egg classified as

unfit for human consumption

Natural Egg Products

Eggs

• Whole hard-cooked, peeled eggs

• Frozen hard-cooked egg rolls

• Scrambled egg mixes

• Frozen omelets

• Frozen fried eggs

Specialty Egg Products

Eggs

• Egg whites, yolk, whole eggs and variety of blends

• Freezing cause textural changes, mainly in the egg yolk

• Functional properties are slightly affected

Freezing Egg Products

Eggs• Causes irreversible gelation• Increases viscosity• Makes difficult to handle and mix with

other ingredients

• Loss of gelation can be prevented by adding sugar/salt up to 10%

Freezing Egg Yolk

Egg Substitutes

• Health benefits (Low cholesterol)• Low cost

• Direct substitutes• Indirect substitutes

Egg Substitutes

• Egg yolk is replaced with other ingredients• Vegetable oil• Non fat dry milk (NFDM)• Vegetable proteins• Gums• Colouring and flavouring agents• Vitamin and minerals

Low cholesterol

Egg Substitutes

• Wheat• Soya• Lupins• Other

Vegetable Proteins

Egg

• Whipping• Emulsifying• Coagulation

Functional Properties

Egg- Functional Properties

• Eggs have the ability to incorporate air and form a relatively stable foam

• Important in Angel food cakes, sponge cakes, pavlova, etc.

• Presence of yolk reduce the whipping ability

• Heat treatment reducesthe whipping ability

Whipping

Egg - Additives

• Added to egg white products• Has little or no effects on whipping

properties of whole egg or yolk• Added to reduce adverse effects on whipping

properties due to pasteurisation, drying and pumping

• Sodium lauryl sulphate, triethyl citrate, etc• Use at about 0.1% based on the egg white

solids

Whipping Aids

Egg- Functional Properties

• Egg yolk and white are good emulsifiers

• Egg yolk is 4 times as effective as egg white as an emulsifier

• Drying of egg products enhances the emulsifying properties

Emulsifying

Egg- Functional Properties

• One of the most important properties of egg products

• The ability of egg products to coagulate and bind pieces of food together or to thicken foods (cakes, puddings)

• Moisture content, pH and other food ingredients influence the coagulation properties

Coagulation

Egg

• To improve texture and/or functional properties (Emulsifiers, gums, etc.)

• To improve free flowing properties (E.g. Sodium aluminium silicate)

Additives

Egg - Additives

• The loss of foaming power of whole eggs and yolk can be prevented by the addition of CHOs to the liquid before drying

• Sucrose, sugar syrups, etc.

CHO

Egg - Additives

• To stabilise frozen egg yolk

• Not extensively used in dried egg products

• Increase shelf life

Salts

Egg – Other UsagesManufacture of Vaccines

Eggs are used to propagate viruses for various vaccines

Culture mediaMicro-organisms grow better if a small amount of egg yolk is added to the culture media

Cosmetics• Shampoos and soaps• Egg cholesterol is used in cosmetics

Egg – Other UsagesUse of Individual Egg Proteins

The egg white has numerous unique proteins which offer opportunities in new technologies– Lysozyme (from egg white): An anti-microbial

agent and pharmaceutical compounds– Avidin-biotin technology is being used in

various medical diagnostic applications such as immuno-assay, histopathology and gene probes