This document discusses dairy foods and dairy products. It begins by describing milk and its composition. Key microorganisms involved in dairy include Streptococcus lactis, Streptococcus cremoris, Leuconostoc citrovorum, and Leuconostoc dextranicum. These microorganisms are used as starters to produce important dairy products like fermented milk, butter, and cheese. Fermented milk products include cultured buttermilk, kefir, and sweet acidophilus milk. Yogurt is produced using Streptococcus thermophiles and Lactobacillus bulgaricus. Cheese is made by separating casein from milk and is classified based on hardness.

1. DAIRY FOODS
Ankita Behera
M.Sc Microbiology
St. George College of Management & Science
Bengaluru North University

2. INTRODUCTION
◦ Milk is considered to be the most perfect food for man and one of the most important
in the diet .
◦ It is an extremely complex mixture and usually contains 87% water and 13% solid.
◦ Of the solids there is average 4% fat and 9% solids other than fat .
◦ It consists 3.3% protein & 5% lactose (protein include casein and albumen).
◦ Milk serve as excellent medium for the growth of bacteria and is contaminated from
various sources.
◦ Micro-organisms play an important role in dairy industry as there are certain micro-
organisms which bring about chemical changes useful in the manufacture of dairy
products.

3. ◦ Each dairy product is produced with the help of selected micro-
organisms . These micro-organisms are commonly known as
“STARTERS”.
◦ The micro-organisms used to produce dairy product are –
I. Streptococcus lactis
II. Streptococcus cremoris
III. Leuconostoc citrovorum
IV. Leuconostoc dextranicum

4. The important dairy product
manufactured are :-
FERMENTED MILK
butter
CHEESE

5. Fermented milk
◦ Fermentation is used to large extent with dairy area. Here, the
purpose is souring and developing flavour substance.
◦ Fermentation is done commonly of the pasteurized milk.
◦ Milk fermentation was done to preserve milk and to provide a new
beverage with a distinctive and desirable flavour .
◦ Consumption of fermented milk is widespread due to its
therapeutic value .
◦ The therapeutic value is that drinking or consuming fermented
milk containing Lactobacillus cause the lactic acid bacteria to
become “implant” in the intestine replacing the putrefying
microflora.

6. The different types of fermented
milk products available in the market
are:-

7. Cultured buttermilk:-
◦ Liquid portion of curd after the separation of butter by churning
process is called “BUTTER MILK”.
◦ It is prepared by directly diluting the curd to the required level .
◦ The starter culture consists of Streptococcus lactis or
Streptococcus cremories together with
◦ Leuconostoc citrivorum or Leuconostoc dextranicum.
◦ The Streptococci develop the acidity and Leuconostoc spp are
responsible for volatile acids and neutral products which give the
characteristics aroma and flavour.

9. Kefir
◦ This is the result of a mixed lactic acid and alcoholic fermentation.
◦ The starter culture is the small granules of organisms called “kefir
grains” which consists of Streptococcus lactis , Lactobacillus bulgaricus
and lactose fermenting yeasts.
◦ Bacteria produce yeasts and yeasts produce alcohol.
◦ It is produced from the milk of cow , goat or sheep.
◦ In addition , Bacillus caucosi grow in nugets and responsible for a
special type of kefir.

11. Sweet Acidophilus milk
◦ It consists of large number of Lactobacillus acidophilus.
◦ To prepare it concentrated cell suspension of Lactobacillus acidophilus
is added to the cold pasteurized milk containing low fat missed well
packaged and then held at a temperature below 40 degree F.
◦ The product has the same flavour as pasteurized milk .

13. Curd (dahi)/yogurt and yogurt like
products:-
◦ these are fermented milk product
◦ Product is obtained from pasteurized or boiled milk by souring and adding harmless
lactic acid bacteria.
◦ Water(85-88%)
◦ Fat(5-8%)
◦ Protein(3.2-3.4)
◦ Lactose(4-6-5.2%)
◦ Lactic acid (0.5-1.1%)
◦ Micro-organisms responsible are Streptococcus thermophiles and Lactobacillus
bulgaricus
◦ Fermentation takes place at 42-46 degree celcius.

15. cream
◦ It is prepared by stirring or centrifugation of whole milk which
results in the separation mostly of the fat content of the milk.
◦ There are 2 types of cream:-
1. Sweet cream (Leuconostoc citrivarum)
2. Sour cream (Streptococcus lactis and Leuconostoc
citrivirum)

17. cheese
◦ Cheese is a milk product produced by separating casein from
milk .
◦ The rest of the milk is in the form of a liquid called “whey”
◦ Whey contains 93%water and 5 %lactose.
◦ As well as smaller amounts of minerals , vitamins ,
lactoalbumin and fats.

18. Depending upon the activity of micro-
organisms the manufacture of cheese
varies:-
◦ They are of 2 types –
◦ Acid curd(its not ripened)
◦ Rennet curd(its ripened by surface growth)

19. On the basis of hardness the cheese is
classified into 3 types:-
◦ Limburger and cambert (soft cheese)
◦ Roquefort and bluecheese (semihard cheese)
◦ Swiss cheese and cheddar (hard cheese)

21. THANK YOU