Milk hygiene

Milk hygiene

Milk hygiene is concerned with the production of clean, wholesome milk that is free from bacteria or other disease causing micro-organisms and maintenance of this condition from farm to the consumers.

In general milk is considered as the most nutritious and complete food for neonates and adult human beings both. An approximate composition of major constituents in milk of different animal origins is given in Table below:    

Table: Percent composition of milk of different animal origins

Source (Animal)	Percent composition
	Total Protein	Casein	Whey protein	Fat	Carbohydrate
Buffalo	4.0	3.5	0.5	7.5	4.8
Cow	3.5	2.8	0.7	3.7	4.8
Goat	3.6	2.7	0.9	4.1	4.7
Sheep	5.8	4.9	0.9	7.9	4.5

Dairy industry provides an excellent example where bacteria, yeasts, moulds and viruses are very important in determining the quality of final product. The control and destruction of undesirable microorganisms, as well as their intentional introduction and utilization are problems that need special attention. The nutritional qualities of milk make it a desirable food for humans and other young animals. However, these nutritional values also permit growth of many microorganisms, some of which cause undesirable changes in milk and its products. Milks sanitary qualities are influenced by many factors in the course of production, processing, and delivery to the consumers.

An example of dairy industry which is dependent to a larger extent on the desirable enzymatic changes caused by microorganisms is cheese making. The flavours and the texture of cheese are largely ascribed to the conversion of milk constituents by various species. Few bacterial and mould species are added intentionally to cheese during manufacturing and much of the microbial activity in that, takes place during ripening are due to microbial species that enter the milk by chance at different stages.

The taste and aroma are competitive assets of butter. Starter cultures; that are mixed bacterial cultures selected for acid- and flavor-producing ability, are important in the manufacture of flavored butter. The conditions in which optimum flavor develops and the relationships with microbes are well known, and certainly the changes brought about by the starters are desirable.

Yogurt, sour cream, and buttermilk are some of the examples of fermented milks made by different intervention of microorganisms to milk, cream, and skim milk, respectively. Each of those products has a characteristic micro-flora that is partly responsible, for its characteristic flavor and texture. It is also possible to ferment milks having desired properties (i.e. flavor and acid-producing) by using starter cultures.

Microbial conversion of certain constituents of milk into economically valuable products like vitamins, solvents, and food adjuncts can be done commercially these days. On the other hand, milk constituents that have no economic significance, or that are usually wasted, must be converted to stably oxidized and non-obnoxious substances prior to their discharge into the environment. Here also microbial activity is responsible for the desired changes in the organic constituents of dairy wastes and of sewage treatment.

Microbes are undesirable in milk or its products, if these deteriorate flavor or texture, and produce diseases. It is important that dairy microbiologists understand the facts that influence the deterioration of milk and the methods through which this type of deterioration can be prevented. Souring of milk or cream is undesirable under majority of situations, but souring (i.e. production of lactic acid) is essential also for the manufacture of cheese or cultured milk products. Discolorations, sliminess, ropiness, putrefaction, rancidity, gassiness, and many other defects are caused by different microbes that grow in dairy products. Milk occasionally has been the carrier of microbes that can cause disease. However, these agents of disease can be effectively controlled. As the new processes and products are developed by the dairy scientists, these must be checked to ensure that these are safe for consumers.

Many ordinances and other regulations under which milk is produced and handled specify quantitative, qualitative, and microbial standards. These standards have shown that under desirable conditions, the numbers of microbes gaining entrance to the product will not exceed certain levels and, also, that proper handling of these products will not permit growth beyond certain levels. To a certain degree, the numbers of microbes permitted on these standards usually are far much below the numbers necessary to cause spoilage. Practically this results into a gradual up-gradation of microbial standards for different dairy products. Because of this type of control, the packaged milk produced by dairy industries is of high microbiological quality and hence, safe to the consumers.