Dairy Ingredients for Food Processing

Chemical, Physical, and Functional Characteristics of Dairy Ingredients 49

levels infl uence curd fi rmness during cheese

making.

Lactose

Lactose is the main carbohydrate in milk. It

is a disaccharide used in pelleting operations

in the pharmaceutical industry, as an anti -

caking agent, and as an agglomerating agent

in foods including confectionery. Lactose

contributes largely to the colligative proper-

ties of milk. It can be used as the reducing

sugar in the Maillard reaction, which is desir-

able in various foods including coffee, bread

crust, and toast. However, it can contribute to

off fl avors in milk.

Lactose can be problematic for individu-

als who suffer lactose intolerance because

they lack the enzyme β - D - galactosidase in

their gastrointestinal tract. Therefore, lactose

is not hydrolyzed, which leads to discomfort

and bloating; however, this can be alleviated

by consumption of yogurt containing probi-

otic microorganisms that contain the β -

galactosidase enzyme. Further, individuals

with galactosaemia are unable to metabolize

galactose. This genetic disorder can only be

treated by eliminating lactose and galactose

from the diet.

Lactulose, Lactosucrose, Lactitol, and

Galactose - oligosaccharides

The derivates from lactose — lactulose, lacto-

sucrose, lactitol, and galactose - oligosaccharides —

have potential prebiotic properties including

enhancing mineral uptake, reducing serum lip-

ids, and reducing the risk of intestinal infec-

tions and colon cancer.

Lactulose is formed from heating lactose,

in which the glucose moiety is epimerized

to fructose. It is recognized as a bifi dogenic

factor. It is present in heated milk (up to

0.2%) but not digestible, and acts as a

soluble fi ber that has been shown to allevi-

ate constipation and chronic encephalopa-

thy, stimulate the immune response, enhance

mixes increases specifi c gravity. Conversely,
an increase in fat lowers specifi c gravity.

Titratable Acidity and pH

Titratable acidity is the amount of alkali or
base required to reach a neutral pH. It is used
to determine compliance with cleanliness
standards and the amount of lactic acid
formed in milk by fermentation. The titrat-
able acidity of whole milk is 13 to 20 mmol/L.
Titratable acidity decreases by heat treatment
due to loss of Ca^2 +^ and rises with increases
in lipolysis.
The pH of milk is between 6.6 and 6.8 at
20 ° C. The pH depends on temperature, and
it decreases with ester hydrolysis. It can be
used as an indicator of bacterial spoilage or
activity. The pH of milk also can be exploited
to separate the whey and casein proteins
because caseins precipitate at pH 4.6.

Functional Properties of Milk

Several constituents of milk have functional
properties both in the formation of other
foods, and in the body. Functional compo-
nents derived from milk include calcium,
immunoglobulins, enzymes, lipids, lactose,
whey and casein proteins, and bioactive
peptides.

Calcium

Whole milk contains approximately 1.2 mg/
ml of calcium. It is required in various roles
of the body including muscle contraction,
blood coagulation, enzyme reactions, hor-
monal secretion, cell signalling stimulation,
and blood pressure control. Calcium also is an
important factor in maintaining healthy teeth
and bones and for protection against various
diseases including osteoporosis, cardiovascu-
lar disease, infectious diseases, colon cancer,
and kidney stones. Technologically, calcium