2009_Book_FoodChemistry

558 11 Eggs
Fig. 11.5. Schematic presentation of the production of egg products
processing steps involved in manufacturing of
egg products.
11.4.2 Technically-Important Properties
The many uses of egg products are basically a result
of three properties of eggs: coagulation when
heated; foaming ability (whippability); and emulsifying
properties. The coloring ability and aroma
of egg should also be mentioned.
11.4.2.1 Thermal Coagulation
Egg white begins to coagulate at 62 ◦ Candegg
yolk at 65 ◦ C. The coagulation temperature is
influenced by pH. At a pH at or above 11.9 egg
white gels or sets even at room temperature,
though after a while the gel liquiefies. All
egg proteins coagulate, except ovomucoid and
phosvitin. Conalbumin is particularly sensitive,
but can be stabilized by complexing it with
metal ions. Due to their ability to coagulate, egg
products are important food-binding agents.
11.4.2.2 Foaming Ability
11.4.2.2.1 Egg White
Whipping of egg white builds a foam which entraps
air and hence is used as a leavening agent in
many food products (baked goods, angel cakes,
biscuits, soufflés, etc.).
Due to a large surface area increase in the
liquid/air interphase, proteins denature and aggregate
during whipping. In particular, ovomucin
forms a film of insoluble material between the
liquid lamella and air bubble, thereby stabilizing
the foam. Egg globulin also contributes
to this effect by increasing the fluid viscosity
and by decreasing the surface tension, both