Selection & composition of milk for cheese making

Presently, I am a second year student of B.Tech Dairy Technology and this is the presentation which I was assigned during the cheese technology course of fourth semester.

1. Topic: Selection and Composition of Milk for Cheese Making Subject: Cheese Technology (DT/405) Presented By: Tiasha Biswas Guided By: Dr. P.D. Sawale Enrollment Number: D/19/007 Roll Number: 06 Dept. of Dairy Technology, College of Dairy Technology ( Pusad )

2. Introduction Selection of the milk plays an important role in the making of cheese. The quality of the cheese depends on the quality of the selected milk. Milk quality influences starter growth , rennet coagulation , manufacturing methods , development of taints and other defects in body and texture of cheese and other changes taking place during ripening of cheese. Milk quality is assessed in terms of sensory , microbiological and chemical quality attributes . As soon as milk is received at the reception dock of the cheese factory, it is evaluated for its odor and appearance . It must not possess any objectionable odor and must be free from extraneous matter . Dept. of Dairy Technology, College of Dairy Technology (Pusad)

3. Quantitative Factors Composition of Milk Composition of milk mainly affects the yield and texture . The milk constituents of prime importance in cheese making are: Dept. of Dairy Technology, College of Dairy Technology (Pusad) milk proteins (particularly casein) milk fat mineral salts (particularly calcium)

4. Milk Proteins Dept. of Dairy Technology, College of Dairy Technology (Pusad) Casein is the major milk protein which exists in micellar form and is composed of α-casein, β-casein, κ-casein and some minor components. The composition and concentration of the components varies in every species, breed, animal health, stage of lactation, etc. These variations affect the cheese making properties of milk, such as clotting time Syneresis proteolysis of cheese curd strength cheese yield composition of the cheese

5. Contd … Lactose and serum proteins are lost in whey during cheese making. So milk high in casein is desirable. But milk high in whey protein may delay clotting time and the casein tends to cause softer curds which lose moisture more slowly. Size of the casein micelle also affects clotting time. Dept. of Dairy Technology, College of Dairy Technology (Pusad)

6. Milk Fat Dept. of Dairy Technology, College of Dairy Technology (Pusad) Alterations in milk fat composition and the amount of milk fat have direct influence on cheese making characteristics and quality of cheese like rennet coagulation time (RCT) coagulum strength flavor and texture of cheese Syneresis Yield cheese composition Increase In fat content of milk gives reduced syneresis and thus longer times are required to achieve desired moisture content in cheese. Low fat in milk poses problem of moisture retention and results in hard and dry body cheese. During ripening, lipolysis of fat results in formation of fatty acids, which impart to cheese, its peculiar flavor.

7. Milk Salts Dept. of Dairy Technology, College of Dairy Technology (Pusad) The salts in milk which are of primary importance to the cheese making process are calcium and magnesium salts of phosphoric and citric acid. Calcium content of milk greatly influences rennet coagulation time, strength of the clot and body and texture of cheese. More calcium content in milk leads to increased micelle size of the casein. Variation in concentration of calcium as well as magnesium, phosphates, citrates and sodium has a direct influence on RCT of milk. High soluble phosphates, citrates and sodium and low soluble calcium and magnesium and also low proportion of casein bound calcium have been found to give slow coagulation of milk by rennet.

8. Qualitative Factors Chemical qualities of milk which affect the cheese quality fall into three main groups: Dept. of Dairy Technology, College of Dairy Technology (Pusad) Quality that inhibits starter growth Quality that affects coagulation Quality that produces taints, gas-holes, etc., in cheese. Milk used for cheese must be free from inhibitory substances of physiological origin, preservatives, and antibiotics. Mixing of mastitis milk, colostrum or late lactation milk adversely affects the time taken for coagulation of milk with rennet. Mastitis milk is low in casein and thus it produces low yield and moist cheese. Late lactation milk is slightly alkaline, high in albumin and chloride and low in casein, lactose and calcium and its effect on coagulation of milk with rennet is similar to that of mastitis milk. Colostrum must not be mixed with the milk at least for three days but preferably up to 15 days as it contains many antimicrobial substances like lactoferrin and lactoperoxidase which causes coagulation delays

9. Natural Inhibitory Substances and Antibiotic Residues in Milk Dept. of Dairy Technology, College of Dairy Technology (Pusad) Presence of inhibitory substances like immunoglobulins , lactoferrin , lysozyme in milk can influence cheese making properties, particularly starter growth and acid development . The presence of antibiotics again affects acid development and may also cause starter failure leading to various defects like high moisture in cheese, early and late blowing , weak and pasty body , cracks , open texture and sponginess .

10. Dept. of Dairy Technology, College of Dairy Technology (Pusad)