• Milk is one of the best available complete food for human beings having a pH value of about 7 is one of the best available food, has high nutritive value.
• The average chemical composition of cow milk based on the analysis of a large no. of milk sample is as follows:

Water:                                                              87.0%

Lactose (Milk sugar):                                        5.0%

Casein (Milk protein):                                       2.5%

Lipid:                                                               4.0%

Albumin & other proteins:                                 0.5%

Vit. A, D, E, & Sterols:                                       0.05%

Miscellaneous:                                                  0.95%

• There are various sources through which milk is contaminated. Milk is free of any microbes in udder of healthy cow but after milked the milk gets contaminated through various ways:
• Utensils
• Air borne micro-organisms settling into the milk
• Water
• Flank of cow, hands etc.

• Good quality milk contains low count of micro-organisms whereas poor quality contains large population of micro-organism.
• So, in order to get good quality milk, hygienic conditions are essential.
• The microorganisms present in the milk may be categorized into 3 groups:-

1. The normal micro flora of most of the milk samples.
2. Some spoilage microorganisms which gain entry into the milk through various sources.

• Some pathogenic microorganisms (to both man and animal) that may be present in unhealthy cow.