Chemistry Reference
In-Depth Information
140
120
100
80
60
Na-C
40
C
20
0
-20
L
-40
hL
-60
70
75
80
85
90
95
100
Weight fraction of solids non-fat ( %)
Figure 11.10.
Glass transition temperature for milk constituents:
C and Na-C: Gordon-Taylor fit for casein and Na-caseinate, respectively (Kalichevsky et al.,
1993),
รพ
: whey proteins isolate (Zhou and Labuza, 2007),
h,
&
,
~
, D: whole milk, skim milk, lactose and skim milk with hydrolysed lactose (Jouppila and
Roos, 1994),
, *: lactose and skim milk with hydrolysed lactose (Shrestha et al., 2007),
L, hL: Gordon-Taylor fits for lactose and skim milk with hydrolysed lactose (Jouppila and Roos,
1994).
Since casein and whey proteins are high molecular weight compounds,
the T
g
value for milk could be expected to be higher than those for lactose.
Likewise, addition of sugars to casein (casein/lactose: 10/1) was reported not
to affect significantly its T
g
(Kalichevsky et al., 1993). It is suggested that
casein and lactose behave as immiscible components, the T
g
of carbohydrate-
rich systems (milk) being governed by lactose T
g
and in casein-rich systems by
casein T
g
(Burin et al., 2002). For mixtures of whey proteins, albumin or
gelatine (lactose/protein: 3/1), T
g
was reported to be slightly higher than for
pure lactose in the dry state, but slightly lower and then again higher with
increasing
humidity
(Haque
and
Roos,
2004).
As
could
be
expected,
