Chemistry Reference
In-Depth Information
and galactose by
-
D
-galactosidase results in milks that are too sweet and
often disliked by consumers. The excessive sweetness of
-
D
-galactosidase-
treated milks has caused some lactose-intolerant subjects to change to soy or
oat ''milks''. The treatment of full lactose milk with
-
D
-galactosidase
increases the chances of Maillard browning, especially in UHT milks
(O' Brien, 1997). The monosaccharides formed from lactose react faster
than lactose with amino acids, resulting in extensive browning; the extent of
the change will depend on the percent hydrolysis. The
-
D
-galactosidase
treatment of fluid milks increases the cryoscopic value of milk from 0.454 to
0.6508C making it difficult to assess the adulteration of milk with water by
cryoscopic methods. Some of the commercially available preparations of
-
D
-galactosidase contain some proteinase activity which is very heat stable
and may not be inactivated by pasteurization or even ultra-high tempera-
ture sterilization of milk, resulting in poor shelf life of the lactose-free milk.
The
-
D
-galactosidase
treatment
increases
the
cost
of
fluid
milk
by
$0.06-$0.08/L.
V.2.1.2.
Lactose-Free Ice Creams
Lactose makes up approximately 20% of the carbohydrates in ice
cream (Marshall and Arbuckle, 1996). The percentage of lactose in ice
cream depends on the formulation, including the amount of non-fat milk
solids and fat in the mixture. Lactose-hydrolyzed ice cream requires less
added sugar to get desirable sweetness as the relative sweetness of lactose is
only one-fifth that of sucrose (Fennema, 1996); hydrolysis of 70% of the
lactose in milk increases its sweetness by an amount comparable to the
addition of approximately 2% sucrose (Zadow, 1986). The monosacchar-
ides produced from lactose depress the freezing point of ice cream mix,
increase relative sweetness and promote the ease of dippability of ice
cream (Iversen, 1983). The freezing point of ice cream mix is directly
proportional to the number of particles in solution (Mitchell, 1989). Linda-
mood et al. (1989) reported that the freezing point of ice cream decreases
proportionately to the extent of lactose hydrolysis in the ice cream mix. The
freezing point of ice cream mix not treated with
-
D
-galactosidase (10% milk
fat, 12% MSNF, 12% sucrose, 5% corn syrup solids and 0.25% stabilizer-
emulsifier blend) was -1.458C while the freezing point of mixes that had
undergone 25, 50 or 100% lactose hydrolysis were -1.62, -1.67 and -1.928C,
respectively (Lindamood et al., 1989). The low freezing point is often
responsible for the accelerated melting of ice cream (Marshall and
Arbuckle, 1996). The hydrolysis of lactose in ice cream results in a smoother
product.
