Microbiology of Milk products (Dairy product)

The important dairy products are:    a) Cheese      b) Yoghurt     c) Butter milk etc.

Cheese:

• Cheese is a dairy product formed by separating casein of milk from the liquid which is called ‘whey’ (Mahi or Chaj in Nepali), Holding most of the fermented and other suspended materials of the milk. Most of the lactose & other soluble milk constitute remain in the ‘whey’.
• Four (4) steps for the preparation of cheese are followed as given below:
• Inoculation of milk with the starter culture for curdling of milk and renin is added for better curdling ( Starter: Streptomyces lactis at 37⁰C).
• Processing of curd
• Salting (add of NaCl)
• Ripening: During ripening process, the degradation of lactose, protein & fat is brought about by activity of microorganisms.

Classification of cheese

A) On the basis of water content:

1. Soft cheese: 50-80% water content
2. Semi hard cheese: (above 45%)
3. Hard cheese: (less than 40%)

B) On the basis of ripening:

1. Unripen cheese: by single step fermentation
2. Ripen/riped cheese: If additional growth is required during maturation of the cheese to achieve the desired taste, texture & aroma.

Several kinds of cheese are known which is shown in table below:-