Dairy Ingredients for Food Processing

Nutritive and Health Attributes of Dairy Ingredients 411

intolerance (maldigestion) may be seen when

milk is consumed following weaning for

several years or after enteric infection.

In the past, it was believed that lactose

maldigesters should avoid milk and dairy

products. However, new evidence shows that

most non - persistent lactase individuals can

tolerate two cups of milk spread over a day

or a cup with meals. They also may choose

lactose - reduced products or low - lactose

products, or use lactase supplements. In the

case of lactose malabsorption, the symptoms

are ameliorated by consuming yogurt con-

taining live and active cultures. Yogurt and

fermented milks furnish the enzyme lactase

to assist in digesting lactose. Lactose - reduced

milk and ice cream products also are avail-

able. By consuming these products, lactose -

maldigesters receive the vital nutrients of

dairy foods, especially, calcium, protein,

vitamins, and minerals.

Minerals

Milk is an excellent source of minerals (Table

16.18 ), including bioavailable calcium. Milk

supplies assimilable calcium and phosphorus

in an optimum ratio. The major source of

dietary calcium is dairy products, supplying

as much as 75% of the dietary intake in

developed nations. The bioavailability of

calcium is further enhanced by the presence

of vitamin D, lactose, and phosphoprotein

(casein). One of the primary functions of

calcium is to provide strength and structural

properties to bones and teeth. Lack of ade-

quate calcium intake, particularly during the

growth phase, leads to osteoporosis or brittle

bones in later life.

Calcium is involved in muscle contraction

(including heartbeat), blood coagulation,

enzyme reactions, stimulation of hormonal

secretions, and cell signaling. It is important

in blood pressure control and it is a factor in

the prevention of colon cancer. Phosphorus

is also critical in bone mass formation, and

takes part in various metabolic processes in

Lactose

Lactose monohydrate, the major carbohy-
drate of milk, ranges from 4.8% to 5.2%.
Lactose stimulates the absorption of calcium
and magnesium. It has a relatively lower gly-
cemic index of 46, as compared to 100 for
glucose and 60 for sucrose. This makes
lactose in skim milk suitable for diabetics
and in weight control diets. It is less cario-
genic than other sugars. Lactulose is a com-
pound formed from lactose in heated milk
products; heated milk contains up to 0.2%
lactulose. Lactulose is not a digestible ingre-
dient; therefore, it acts somewhat like a
soluble fi ber. Lactulose is generally used to
treat constipation and chronic encephalopa-
thy. Recent data indicate that lactulose may
enhance calcium absorption in the intestine.
It stimulates the growth of Bifi dobacterium
bifi dum and is thereby benefi cial in establish-
ing useful microfl ora in the gut.
Certain ethnic groups in the United States,
particularly a majority of African Americans,
Asians, and Southern Europeans, experience
symptoms of lactose intolerance, including
bloating, fl atulence, abdominal pain, and
diarrhea, after consuming milk and milk
products. Lactose intolerance is mainly
attributed to discontinuation of milk con-
sumption after infancy, as seen in the dietary
pattern of such ethnic groups. In such cases,
epithelial cells in the intestinal mucosa tend
to lose the ability to secrete lactase enzyme
due to absence of lactose in the diet. Lactase
is a non - persistent enzyme in certain indi-
viduals, resulting in the distressing symp-
toms following milk intake. Lactase, or
β - galactosidase, is a key enzyme in digestion
of lactose. It catalyzes the hydrolysis of
lactose to glucose and galactose, which are
rapidly absorbed. Temporary absence of
lactase from the digestive tract also may be
exhibited during or following enteric infec-
tions, when the surface lining of intestinal
mucosa is damaged due to invasion of entero-
pathogenic bacteria. Symptoms of lactose