Dairy Ingredients for Food Processing

Whey-based Ingredients 193

foods to provide the body and mouth feel of

fat without the addition of fat.

Heat Stability

Many whey protein ingredients are used in

retorted nutritional products (infant or enteral

formulas). These products are usually given

heat treatments of about 120 ° C (248 ° F) for

15 minutes to sterilize them, allowing a

shelf life of around two years for some prod-

ucts. The ability of the proteins to stay in

solution during the heating step is crucial,

requiring specifi c treatments to the complex

formulations.

Foaming and Whipping

Foaming of protein solutions can be desirable

in some applications (e.g., aerated products

such as desserts and meringues) but is unde-

sirable in other applications (such as fruit

juice fortifi cation or in the brine pumping of

hams).

The formation of foam is a multi - stage

process involving denaturation of protein,

adsorption to the air/water interface, entrap-

ment of air, repair, contact - stabilization, and

coagulation - destabilization of the foam.

The speed of air incorporation and the sta-

bility of the foam depend on parameters such

as whey protein type, protein denaturation

level, fat content, protein and carbohydrate

concentrations, concentrations of calcium

and other ions, pH, and equipment (Morr and

Foegeding 1990 , Farrag 2008 ). The presence

of fat is particularly detrimental to the forma-

tion of foams due to the hydrophobic disrup-

tion of the surface tension of the fi lm, and

whey protein ingredients with reduced fat

content such as WPIs show the best perfor-

mance where foam formation is required.

Viscosity and Water Binding

The viscosity of whey protein ingredients

in water is low, which allows the use of

• Temperature - time profi le during processing


• p H


• Total solids


• Ionic strength and composition

Gelation

Under appropriate heating conditions, whey
proteins form irreversible gels by restructuring
into extended three - dimensional networks.
Heat gelation of whey proteins is gener-
ally recognized as a two - or three - stage
process: denaturation of the native globular
structure into a partially unfolded state, fol-
lowed by aggregation of the denatured
protein into a gel matrix, which can bind
large amounts of water (De la Fuente et al.
2002b , de Wit 2009 ). However, a delicate
balance between attractive and repulsive
forces is required to give the desired gel.
Whey proteins start to gel when heated to
around 65 ° C (149 ° F). A strong gel network
helps to hold the water and prevent moisture
loss (syneresis). This property improves the
yield value of various food products (e.g.,
ham) and can also improve the appearance by
preventing surface moisture (e.g., yogurt).

Emulsifi cation

The formation of emulsions is important in
a number of applications in which fat or
oil is present (e.g., salad dressings). Whey
proteins are candidates for emulsifi cation
because the proteins have both hydropho-
bic regions and hydrophilic regions. Whey
proteins are thought to form interfacial mem-
branes around oil or water globules, pre-
venting creaming, coalescence, and oiling
off. After adsorption at the fat or water inter-
face, the protein partially unfolds to stabilize
the globules. Whey proteins maintain their
solubility under acidic conditions; therefore,
they can perform well where many other pro-
teins cannot (Fachlin and Viotto 2005 ). Whey
protein ingredients also are useful in low - fat