Dairy Ingredients for Food Processing

192 Chapter 8

lates have poor solubility below pH 4.5 and

so are less suitable for low - pH foods if solu-

bility is a requisite.

The solubility of proteins is lowest at their

isoelectric pH (when the protein has a net

charge of zero). Because the overall isoelec-

tric pH of the whey proteins is in the region

of pH 5, there is a slight dip in the solubility

of whey proteins at pH 5 (Kilara, 2008 ).

One particularly important factor affect-

ing the solubility of protein products is the

level of whey protein denaturation. The dena-

turation of whey proteins is generally a func-

tion of the amount of heat treatment that the

protein has received, although other factors

such as shear and foaming are also relevant

(Mangino et al. 1988 ).

Heat treatments have an additive effect on

whey protein denaturation, with temperatures

as low as 55 ° C (131 ° F) leading to denatur-

ation over time. Therefore, good control of

upstream processing is very important (Patel

et al. 1990 ). Very small amounts of whey

protein denaturation lead to enhanced water

and fat binding by WPCs. Such products may

present enhanced viscosity, lower gelation

temperatures, enhanced emulsifi cation, and

cold setting (Schmidt et al. 1984 , Abd El -

Salam et al. 2009 ).

Factors affecting whey protein denatur-

ation include:

Functional Properties of Whey

Protein Concentrates

According to Huffman (1996) , whey protein
products possess a number of functional and
nutritional properties in varying degrees
(Table 8.6 ). However, no single whey protein
can be used in a wide spectrum of food prod-
ucts because very few proteins exhibit the
needed multiple functionalities (Abd El -
Salam et al. 2009 ). Mangino (1992) , Kilara
(2008) , and Abd El - Salam (2009) have
reviewed and assessed the functional proper-
ties of a variety of whey protein ingredients
and the processes to manufacture those
ingredients.

Solubility

Solubility is probably the key property of
most whey ingredients. If the product is not
soluble, the other properties are usually also
poor.
Whey proteins demonstrate excellent sol-
ubility over a wide pH range. Because most
food systems have pH values in the range of
3 to 7, it follows that whey protein ingredi-
ents will remain soluble in practically all
liquids and most foods unless heated. The
advantage of whey proteins over other protein
systems, e.g., caseinates and soy protein iso-
lates, is that caseinates and soy protein iso-

Table 8.6. Defi nition of terms for protein functional properties related to food systems.

Property Defi nition Food System

Solubility Ability to remain in solution over a broad

pH range

Beverages, yogurt, salad dressings

Gelation Ability to form a stable, cohesive gel when

heated

Pumped meats, baked goods, cheese

Emulsifi cation Ability to keep two solutions that are not

soluble in each other in a stable

suspension

Infant formula, salad dressing, soup

Heat stability Ability to remain in solution during heating Infant formula, beverages

Whipping Ability to form stable foams Cakes, whipped desserts, ice cream

Water and fat binding Ability to bind water, or entrap water, or

bind free fat

Sausages, pumped meats

Nutrition Protein amino acid profi le and bioactivity Infant formula, nutritional beverages,

nutritional supplements

Adapted from Mangino (1992) , Huffman (1996) , de Wit (1998)