Dairy Chemistry And Biochemistry

32

LACTOSE IN SOLUTION

a-b

[Pl/[al= 1.64-0.0027T

DAIRY CHEMISTRY AND BIOCHEMISTRY

L

.-

Amorphous Lactose

V

a-Hydrate

(lactose. I.H,O)

Conipound crystal

asp3 (anhydrous)

[ p] / [a] = 1.25 I

T = IOW, presence^1

01 \vay

LI I

Anhydrous a

unstable

-1

Water uptake, T < !USo

I

stable (S)

TI 150", presence

01 water vapour

Dissolve, T c 93.5'

.......................

Silpersatiiration in ethanol

Figure 2.8 Modifications of lactose (T temperature in 'C) (from Walstra and Jenness, 1984).

monohydrate. These crystals are small, usually with dimensions of less than
1 pm. Crevices and cracks exist along the edges of the crystals, into which
other components are expelled. In these spaces, favourable conditions exist
for the coagulation of casein because of the close packing of the micelles and
the destabilizing action of concentrated salt systems. The fat globule
membrane may be damaged by mechanical action, and Maillard browning,
involving lactose and amino groups of protein, proceeds rapidly when
crystallization has occurred.