What Is Dairy Microbiology?

In this what is dairy microbiology? post we have briefly explained about dairy products, source of microorganisms, and standard and grading of milk.

The branch of biology that deals with the study of microorganisms and their different metabolic activities is termed as Microbiology. The microorganisms are playing a very important role in human civilization ad their development. They play an important role in food dairy, Environment till and destruction of microorganisms.


The study of Microorganisms that are associated with milk and milk products in all aspects is defined as Dairy Microbiology. In milk microorganisms play a vital role in production of many products. The area of dairy microbiology is large and diverse. The bacteria in dairy products may cause disease or spoilage. Some bacteria may be specifically added to milk for fermentation to produce products like yoghurts and cheese.

What is Milk?

Dairy microbiology

Milk Products

Milk is the white, fresh clean lateral secretion obtained from female cattle. Milk is used for the nourishment of their younger ones. It is in liquid form without having any colostrum. The milk contains water, fat, protein and lactose. About 80-85% of the proteins is casein protein. Due to moderate pH (6.6), good quality of nutrients, high water contents etc. make milk an excellent nutrient for the microbial growth. It is mainly the udder interior, teats surrounding environment and manual milking process make the source of contamination.


1. Udder

The milk producing animals should be kept neat and clean. More care should be taken to keep the flanks, udder and teats clean. The interior of the teats of the udder is warm and contains the last remains of the milk which has more microbes which would have entered through opening of teat and multiplied.

2. Cow Skin

Soil, faeces and dirt adhere to the skin and hairs of the cow. Hair, dirt and dust fall in to milking utensils or into the teat cups of milking machines. Most of the organisms from these sources are gas producers and putrefactive types. Faeces contain enormous quantity of organisms and most of them are pathogenic microorganisms.

3. Utensils

Milking utensils and equipment’s are the major sources of contamination of milk. They have to be washed properly with detergent. Further the utensils and equipment’s should be cleaned with hot water, air and steam to remove all the spore forming, fluorescent and coliform microorganisms.

4. Feeds

Microorganisms are found everywhere. They are present in abundant in vegetation and soil. Dry feeds have more amount of bacteria and less amount of fungi. These organisms contaminate the milk.

5. Cow shed

The air of the cow shed is greatly contaminated by dry dirt and dust. During the mixing of feeds and during the cleaning process of the floor, the air of the cow shed is highly contaminated and it is passed on to the milk.

6. Milking person

Pathogenic microorganisms may enter into the milk through milking persons. They should wear clean clothes and properly wash their hands before milking. Nails should be cleaned and trimmed. Discharge from sneezing, coughing and nose blowing should not reach the atmosphere, equipment or the milk. Some of the organisms may be carriers of diseases.

7. Water

Pure water should be used for cleaning purposes. Water exposed to contamination spreads the microorganisms. Water should be free from coliform organisms. Chlorination of water prevents such contamination.

Standard and Grading of Milk

The Food and Drug Administration (FDA) has prescribed microbiological standard for quality of milk.

Dairy microbiology

New York State milk standards (New York Ag and Markets, 2006) are based on those defined in the FDA Pasteurized Milk Ordinance (PMO, 2017). 

Grading of milk

The quality of milk is judged by certain standards and it is known as grading milk. Grading of milk is based upon regulations pertaining to production, processing and distribution.

This includes sanitation, pasteurization, holding conditions and microbiological standards. The U.S public health secrine publication “Milk ordinance and code” shows the following chemical, bacteriological and temperature standards for grade A milk and milk products.

Further Readings