Handbook of Food Science and Technology 3

1.3. Dairy product technology 
The processing of milk into dairy products is based on the influence of 
biochemical (composition), physicochemical (pH, ionic strength, intensity 
[time/temperature] of the heat treatment) and biological factors (enzyme or 
flora action) on the stability of milk. A distinction can be made between: 
– products for which a high level of biological and physicochemical 
stability is desired (liquid milk, milk powder); 
– products, such as fermented milks, which associate the physicochemical 
destabilization of the milk during acid coagulation and its biological stability 
up to consumption (risk associated with the presence of pathogens, exudative 
phenomena and post-acidification); 
– products resulting from the separation and concentration of all or part of 
the more valuable fractions of milk (protein and/or fat) by exploiting their 
instability (butter, cheese).
1.3.1.
 Liquid milk 
The changes in technological processing, preservation techniques and 
distribution have allowed the development of a wide range of liquid milk (i.e. 
drinking milk) that differs in its composition, nutritional and sensory quality 
and shelf-life. Global market trends show a strong decrease in the 
consumption of whole milk (3.6% fat (w/w)) in favor of semi-skimmed milk 
(1.5 – 1.8% fat (w/w)), skimmed milk (less than 0.3% fat (w/w)) and “special” 
milks (infant formula milk, milk fortified with vitamins, calcium, phosphorus, 
magnesium and/or fiber, organic milk, growth milk, flavored milk, lactose-free 
milk, etc.). 
Milk for human consumption can be currently classified into three 
categories: 
– untreated raw milk; 
– heat-treated milk; 
– microfiltered milk. 
These milks are only subject to physical treatment such as fat and/or 
protein, mineral and vitamin standardization, homogenization to avoid 
creaming, and heating or cross-flow microfiltration to reduce microorganisms.

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26 Handbook of Food Science and Technology 3 
1.3.1.1.
 Raw milk 
The production and sale of raw milk must be highly controlled due to 
potential health risks. Milk should come from: 
– registered healthy animals free from brucellosis and tuberculosis; 
– registered farms, subject to strict veterinary control; 
– a process (milking, packaging, storage) that is carried out under good 
hygienic conditions.
Authorities specify the conditions of production and the microbiological 
quality standards of raw milk.
1.3.1.2.
 Heat-treated milk 
Depending on the intensity of the heat treatment (see Chapter 4,
Volume 2), a distinction can be made between: 
– pasteurized milk; 
– long-life milk. 
Pasteurized milk
Pasteurization is used to destroy all pathogenic microorganisms in milk 
(Figure 1.9). The destruction of tubercle bacillus is often taken as a reference 
for the choice of pasteurization level. Pasteurization levels are defined by 
equivalent temperature/time relationships based on a z value of 5°C: the time 
is reduced by a factor of 10 for a temperature increase of 5°C.