Dairy Ingredients for Food Processing

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Chapter 7

Casein, Caseinates, and Milk Protein Concentrates

Mary Ann Augustin , Christine M. Oliver , and Yacine Hemar

Introduction

Milk is a complex fl uid. Typically bovine
milk has about 12.5% total solids, the major
components of which are the proteins (3.5%),
fat (3.8%), and lactose (4.6%). The main pro-
teins in milk are the caseins and the whey
proteins. The ratio of casein : whey protein
is approximately 4 : 1. Milk also contains
mineral salts (0.7%) and many other minor
components. Although the mineral salts are
minor components, they have a major infl u-
ence on the functional properties of the milk
proteins.
Milk proteins are valued ingredients with
high nutritional value and a range of physical
functional properties that make them sought -
after ingredients for foods. In the dairy indus-
try, milk is often separated to obtain fractions
of protein products. The development of milk
protein fractions has enabled the dairy indus-
try to diversify its range of protein products.
Among some of the differentiated dairy
protein products are the caseins and casein-
ates, whey protein products, such as whey
protein concentrates and isolates, and milk
protein concentrates, which contain both the
casein and the whey proteins in the ratio at
which they occur in normal milk.
This chapter discusses the casein - based
milk protein products — caseins, caseinates,

and milk protein concentrates. The chemistry

of casein and the casein micelle, process-

ing methods for manufacture of casein - based

milk protein products, their composition,

functional properties, and applications in

dairy and non - dairy food products are

covered.

Chemistry of Caseins

Caseins are novel, milk - specifi c, acid -

insoluble phosphoproteins that encompass

approximately 80% of the total protein in

milk. They are readily separated from the

other milk proteins (i.e., the whey/serum pro-

teins) by isoelectric precipitation of casein at

pH 4.6, 30 ° C (86 ° F) (Fox and Kelly 2004 ).

Casein consists of four major protein frac-

tions: α (^) s1 - , α (^) s2 - , β - , and κ - casein, which have
molecular weights between approximately
19 and 25 kDa, and occur in an approximate
4 : 1 : 4 : 1 weight ratio in bovine milk (Fox
and Kelly 2004 ). Fragments of casein, caused
by the action of plasmin and which are known
as γ - caseins, are also present in milk (Fox and
Kelly 2004 ).

The Individual Caseins

The primary structures of the caseins have

been established and numerous genetic vari-

ants of each of the caseins have been identi-

fi ed (Farrell et al. 2004 ). Extensive detail on

the physicochemical properties of the indi-

vidual caseins is reported (Kinsella 1984 ).

Several salient features of the caseins are

Dairy Ingredients for Food Processing edited by
Ramesh C. Chandan and Arun Kilara
© 2011 Blackwell Publishing Ltd.