Chemistry Reference
In-Depth Information
hydrolysis of lactose induces an important decrease of the glass transition
temperature of milk (Figure 11.10) (Jouppila and Roos, 1994; Fernandez
et al., 2003; Shrestha et al., 2007).
11.4.
Water Retention
As was nicely summarized by Van Vliet and Walstra (1994) ''Water in Casein
Gels; How to Get It out or Keep It in'', an important problem regarding high
water content dairy products is to prevent syneresis of liquid from products
such as yoghurt and gelified dairy desserts, or to remove just the required
amount of water in the case of cheese production. Gels may hold considerable
amounts of water, part of it being difficult to remove by pressing, centrifuging
or drying. This observation has led to the belief that part of the water is bound
to the molecules (particularly proteins) forming the gel network. It may be
observed, first, that this holding ability is not connected to a low water
activity. From Figure 11.11, one can see that lowering the water content of
Figure 11.11.
Water sorption isotherm for paracasein (3) and desorption isotherms for salted
(1, 12.6 g NaCl/l00 g protein) and unsalted (2, 0.4 g NaCl/l00 g protein) cheese (Van Vliet and
Walstra, 1994).
