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Dairy microbiology
- 1. DAIRY MICROBIOLOGY • Microorganisms inmilk • Milk products.
- 2. Dairy microbiology ◦ Studyof microorganisms in relation to milk and milk products. ◦ It deals with normal microbial flora of milk ,pasteurization, making dairy products.
- 3. MILK ◦ White, fresh,clean. ◦ Primary source of nutrition. ◦ Liquid forms ◦ It contains water, fat, protein and lactose. ◦ Provide growth to microorganisms.
- 4. PHYSICAL AND CHEMICALPROPERTIES OF MILK ◦ Milk is a white emulsion or colloid or butter fat globules. ◦ It contains many other nutrients. ◦ It contains 30-35 grams of protein. ◦ Different carbohydrate including lactose, glucose, galactose and other oligosaccharides. ◦ Ca, mg, Na, k, citrate and cl all are included. ◦ Vitamins A, B,C,D,E, thiamine, biotin, riboflavin are all present in milk.
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- 6. MICROORGANISMS IN MILK ◦Excellent nutrient for microbial growth. ◦ Supports the growth of a variety of bacteria including pathogens.
- 8. IMPORTANT MICROORGANISMS IN MILK ◦Bacteria ◦ Yeasts ◦ Molds.
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- 10. BACTERIA ◦ Major sectionof microorganisms. ◦ Study of bacteria in relation to milk and milk products- DAIRY BACTERIOLOGY. ◦ Produce desirable and undesirable changes in milk and milk products. ◦ Eg: Bacillus subtilis.
- 11. YEASTS ◦ Act onlactose and produce ACID and CARBONDIOXIDE ◦ SOURCE: feed, soil. ◦ Lipolytic in action. ◦ EG: Torula cremoris, Torula lactis, Saccharomyces cerevisiae.
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- 13. MOLDS ◦ Undesirable odour. ◦Contaminate and grow in large numbers on the surface of butter, cream, khoa and cheese. ◦ Colour- black, grey, blue or white. ◦ Proteolytic/lipolytic. ◦ EG: Penicillium sp.
- 14. CLASSIFICATION classification. Biochemical type temperaturecharacteristics pathogenic type
- 15. BIOCHEMICAL TYPE OF MICROORGANISMS ◦Acid producers ◦ Gas producers ◦ Ropy or stringy fermentation type ◦ Proteolytic type ◦ Lipolytic type ◦ Acetic acid type ◦ Butyric acid ◦ Production of abnormal colour in milk.
- 16. BIOCHEMICAL TYPES Acid producers ◦Produces acid. ◦ EG: STREPTOCOCCI: It is a spherical bacteria. Streptococcus lactis- produce normal souring of milk. Streptococcus cremoris – good flavor to ripened cream. Streptococcus thermophilus – occurs in pasteurized milk. It is used in yoghurt preparation.
- 17. BIOCHEMICAL TYPES Acid producers ◦COLIFORMS: ◦ Source- manure, polluted water, soil and plants. ◦ It is a facultative anaerobes. ◦ It cause rapid spoilage to milk. ◦ EG: E. coli.
- 18. BIOCHEMICAL TYPES Gas producers ◦Form ferment lactose with the accumulation of gas. ◦ These gas may be carbon dioxide/ mixture of carbon dioxide and hydrogen. ◦ EG: Coliform sp, clostridium butyricum, Torula cremoris.
- 19. BIOCHEMICAL TYPES Ropy orstringy fermentation type ◦ SOURCES: soil, water, plants and food. ◦ Synthesize a viscous polysaccharide material. ◦ Eg: Alcaligenes viscolactis, Enterobacter aerogenes.
- 20. BIOCHEMICAL TYPES Proteolytic microorganisms ◦Coagulate casein by the enzyme RENIN. ◦ SOURCES – soil, water and utensils. ◦ Responsible for sweet curdling and peptonization of milk. ◦ EG: Bacillus subtilis, Bacillus cereus, Pseudomonas sp., Streptococcus liquefaciens.
- 21. BIOCHEMICAL TYPES Lipolytic type sources– soil, water, dairy utensils. • Hydrolyze milk fat into glycerol and fatty acids. • Some fatty acids produce rancid odour and taste to milk. • EG: Pseudomonas fluorescenes, Candida lipolytica, Penicillium sp,
- 22. BIOCHEMICAL TYPES Acetic acidtype ◦ Combination with yeasts and lactic acid bacteria. ◦ EG: Acetobacter aceti, Acetobacter kutzingianum, Acetobacter pasteurianum.
- 23. BIOCHEMICAL TYPES Butyric acid ◦SOURCES- faeces, soil, water. ◦ Eg – Bacillus welchii ◦ Produce butyric acid and small quantities of propionic acid, formic acid, hydrogen, carbon dioxide,. ◦ Milk is curdled slowly.
- 24. BIOCHEMICAL TYPES Production ofabnormal colour in milk ◦ Certain bacteria produce abnormal colour when they grow in milk. When such milk is exposed to air, it leaves carbon dioxide and absorbs oxygen. ◦ EXAMPLE- Bacillus cyanogenes- produce dirty brown colour in sterile milk. Torula glutinus- pink or red colour. Bacillus prodigiosus- red colour.
- 25. TEMPERATURE CHARACTERISTICS OF MILK ◦Psychrophilic type- bacteria grow at very low temperature. EG- Flavobacterium sp., ◦ Mesophilic type- organisms grow at moderate temperature between 10 and 30’c. EG- Streptococcus sp., ◦ Thermophilic type- well in temperature above 30’c.EG- Bacillus sp., ◦ Thermoduric type- grow at above 62’c and can survive even after pasteurization. EG- Microbacterium lactis, etc.
- 26. PATHOGENIC TYPE OFBACTERIA MILK o Source- cow/man. o Milk-borne disease. o EG- Streptococci . When cows are infected with streptococci in the udder ,it will transfer into milk and cause diseases.
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- 28. Milk products ◦ Productssynthesized from milk – MILK PRODUCTS/ DAIRY PRODUCTS.
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- 30. CHARACTERISTICS OF FERMENTED MILKS FERMENTED PRODUCT RAWMATERIAL MICROORGANISM RESPONSIBLE FOR FERMENTATION REMARKS Cultured butter milk Pasteurized skim milk Streptococcus lactis Leuconostoc citrovorum Lactic acid fermentation kefir Whole milk Streptococcus lactis Lactose fermenting yeast Alcoholic and lactic acid fermentation. Kumiss Mare’s milk Lactobacillus bulgaris Streptococcus lactis A mixed acid-alcoholic fermentation products using mare’s milk (in Russia) yogurt Whole milk Streptococcus thermophilus Lactic acid fermentation
- 31. IMPORTANT FERMENTED MILK Anumber of milk products viz., cheese, yogurt, milk powder, cream, butter, etc., are produced from milk. o Examples of milk products: 1)YOGURT
- 33. YOGURT ◦ Turkish word-JUGURT. ◦ Most popular fermented milk ◦ Made from skimmed milk, milk . ◦ Milk should be free from contamination. ◦ Example: Lactobacillus bulgaricus, Lactococcus thermophilus helps to produce yogurt.
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- 35. CURD o Fermented milkproduct. o Pasteurized milk or boiled milk o Fermented by harmless lactic acid bacteria or other bacterial culture which is retained from the previous days curd (starter). o Two types- churning into desi butter, direct consumption prepared from whole milk or skimmed milk.
- 36. BUTTER ◦ Fat concentrate ◦Obtained by churning cream or curd with or without salt. ◦ Example- Desi butter. ◦ Butter with 10 yeasts and molds per gram and less than 50 proteolytic bacteria per gram is considered as GOOD BUTTER. ◦ Eg-Leuconostoc citrovorum.
- 37. ACIDOPHILS MILK ◦ Wholeor skimmed milk is fermented with Lactobillus acidophilus which have benefits in the gastrointestinal tract.
- 38. CHEESE ◦ It isa milk product produced by separating casein from milk. The rest of the milk is in the form of whey. ◦ Classification: 1. On the basis of coagulation 2. On the basis of hardness.
- 39. MANUFACTURE OF CHEESE ◦INOCULATION OF MILK ◦ CURDLING ◦ PROCESSING OF CURD TO REMOVE MOISTURE ◦ SALTING ◦ RIPENING
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