Dairy Chemistry And Biochemistry

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1

DAIRY CHEMISTRY AND BIOCHEMISTRY

I

CHPOH

HO HpHR - L

Glycosylamine

C-NHR

c=o

I

L

.

HvNR

C

I

C-

I-

t-

\ JNHR

II

C-OH

1-Amiiio-2-kcto sugar

Figure 2.30 Arnadori rearrangement of a glycosylamine.

2.6 Nutritional aspects of lactose

Since the milks of most mammals contain lactose, it is reasonable to assume
that it or its constituent monosaccharides have some nutritional signifi-
cance. The secretion of a disaccharide rather than a monosaccharide in milk
is advantageous since twice as much energy can be provided for a given
osmotic pressure. Galactose may be important because it or its derivatives,
e.g. galactosamine, are constituents of several glycoproteins and glycolipids,
which are important constituents of cell membranes; young mammals have
a limited capacity to synthesize galactose.
Lactose appears to promote the absorption of calcium but this is
probably due to a nonspecific increase in intestinal osmotic pressure, an
effect common to many sugars and other carbohydrates, rather than a
specific effect of lactose.
However, lactose has two major nutritionally undesirable consequences

• lactose intolerance and galactosaemia. Lactose intolerance is caused by
  an insufficiency of intestinal P-galactosidase - lactose is not completely