Chemistry Reference
In-Depth Information
crystallization have been suggested to ice cream manufacturers for many
years (Sommer, 1944; Nickerson, 1962); however, the modern use of poly-
saccharide stabilizers, as discussed below, renders obsolete some of the older
recommendations for MSNF in formulations. Lactose content is certainly a
consideration in the use of MSNF ingredients, such as whey powder, perme-
ate or other MSNF sources that contain an elevated level of lactose.
Nickerson and Moore (1972) showed that increasing sucrose concentration
reduces lactose saturation, exacerbating the propensity for crystallization. On
the other hand, sucrose may inhibit the lactose nucleation process, thereby
promoting supersaturation (Livney et al., 1995). Ingredients like dextrins
from low DE corn syrup solids, soluble milk proteins and polysaccharide
stabilizers, all of which promote solution viscosity, would be expected to have
an inhibitory effect on lactose crystallization. This is one of the important
contributions of the polysaccharide stabilizers to ice cream quality (Marshall
et al., 2003). Some flavours, especially those with nuts, seem to be associated
with a higher incidence of lactose crystallization (Nickerson, 1954, 1962;
Marshall et al., 2003). Explanations may be the inclusion of fine particles
that act as nucleation sites for lactose or localized differences in water con-
centration as nuts absorb water during storage. The most important storage
parameter is temperature. Livney et al. (1995) showed that the induction time
for lactose crystallization was reduced to a minimum (highest propensity for
sandiness) as the temperature was lowered from -58 to -128C but the induc-
tion time increased again at temperatures lower than -128C. Increasing super-
saturation increased the driving force as temperature was reduced but at
-128C this was offset by increasing viscosity. Crystal growth rate also fol-
lowed a similar trend. Nickerson (1962) and Livney et al. (1995) also showed
the increasing effect of temperature fluctuation on lactose crystallization
which is completely inhibited as the unfrozen phase approaches or enters
into the amorphous solid (glassy) state, at approximately -25 to -308C.
III.5.
Development of Lactose-Reduced Products
The consumption of lactose can be problematic for many people, due to
lactose malabsorption or intolerance (see Chapter 6). Consequently, there is
a significant market for reduced-lactose ice creams and frozen dairy des-
serts. The two approaches are enzymatic hydrolysis of lactose, either in the
mix itself or from the use of lactose-hydrolyzed ingredients, and the selec-
tion and blending of milk fat and MSNF ingredients to reduce the level of
lactose.
Hydrolysis of lactose either in the mix or in MSNF ingredients for use in
ice cream has been studied by several researchers (Guy, 1980; Young et al.,
