166 Chapter 7
the natural micellar form of casein during
manufacture.
There is no pH adjustment involved in
the process. The fresh, liquid micellar
casein concentrate has three - fold the protein
content of skim milk (Barbano 2004 ). The
micellar casein can be readily spray dried
into a powder form. Casein can also be re -
micellized using acid casein with pH adjust-
ment to 7 and concomitant re - introduction of
CCP (Mounsey et al. 2005b ). Re - micellized
casein has intrinsically higher ionic strength
than native micellar casein, which impacts
its functional properties (Mounsey et al.
2005b ).Caseinates
Types of Caseinate Products
Caseinates are the water - soluble forms of the
casein, obtained by addition of alkali to
freshly precipitated casein or dry casein
powder. Various types of alkali may be used.
When sodium hydroxide is used as the solu-
bilizing alkali to neutralize the casein slurry,
the resulting product is called sodium casein-
ate. Similarly, potassium, calcium, or ammo-
nium caseinate are produced when potassium,
calcium, or ammonium hydroxide, respec-
tively, are used as the neutralizing agent. The
caseinate solution is then dried using either a
spray or roller dryer to produce a powder
with a moisture content ranging between 3%
and 8% (Southward 1985 ).
Sodium caseinate, ammonium caseinate,
and potassium caseinate have similar physi-
cal properties. Their aqueous solutions are
translucent, straw - colored, and viscous. In
contrast, solutions of calcium caseinate are
turbid (milky) because calcium caseinate
forms aggregates in water. The increase in
turbidity and decreased viscosity is due to
the change in conformational and aggrega-
tion mode of the casein molecules in the
presence of the calcium ions (Alvarez et al.
2008 ).Typical Compositions of Commercial
Casein Products
The typical composition of rennet casein and
acid casein are provided in Table 7.2. The
major difference between rennet casein and
acid casein is their mineral (ash/calcium)
content and the pH of a water extract. During
the acidifi cation process in the manufacture
of acid casein, the calcium and inorganic
phosphate associated with the casein micelles
in milk are dissolved and leached from
the curd, leaving only a small residue of
calcium and the organic phosphate. Rennet
casein contains approximately 3% calcium
and 1.4% phosphorous (Southward 1998 ).
Native micellar casein is reported to have
a similar composition to that of calcium
caseinate, with 90% total protein (Fox and
Kelly 2004 ).
Micellar Casein
Micellar casein, also called phosphocasein, is
produced from milk by microfi ltration per-
formed on membranes with an average pore
size of 0.1 to 0.2 μ m (Fox and Kelly 2004 ).
Microfi ltration results in the removal of the
whey proteins, lactose, and soluble salts
with retention of the micellar casein and its
associated CCP. This is in contrast to when
casein is separated from the whey proteins
by isoelectric precipitation of the casein
or rennet - induced coagulation , which disrupt
Table 7.2. Typical composition of casein prod-
ucts. Southward (1998).
% Component Rennet casein Acid casein
Protein 79.9 85.4
Moisture 11.4 11.4
Ash 7.8 1.8
Fat 0.8 1.3
Lactose 0.1 0.1
Calcium 2.6 – 3.0 0.1
Phosphorus 1.4 0.6
Sodium < 0.1 < 0.1
pH 7.3 – 7.7 4.6 – 5.4