Methods of preservation of milk and milk products

Raw milk: The lacteal secretion , practically free from colostrum,
obtained by the complete milking of one or more
healthy cows (PMO).

1. Methods of preservation of milk and milk products Dr.D.KANCHANA MICROBIOLOGY

2. Definitions Raw milk: The lacteal secretion , practically free from colostrum, obtained by the complete milking of one or more healthy cows (PMO). “Consumer Milk” products: - Homogenized milk:  3.25% fat - Reduced fat milk: 2% fat - Low fat milk: 1% fat - Fat-free milk: skim milk, <0.5% fat (all with 8.25% solids-non-fat) Other “milk products”: lactose reduced milks, heavy cream, cultured milks, yogurt, cottage cheese.

3. Contamination of milk and milk products

4. Milk is sterile at secretion in the udder but is contaminated by bacteria even before it leaves the udder. Further infection of the milk by microorganisms can take place during milking, handling, storage, and other pre-processing activities.

5. Few types of micro organisms found in milk. Streptococcus lactis Achromobacter Coliform bacteria Bacillus subtilis

6. Preservation of milk

7. Methods of preservation

8. Purpose: Inactivation of bacterial pathogens (target organisms Coxiella burnettii ) - assurance of longer shelf life (inactivation of most spoilage organisms and of many enzymes) Pasteurization Heat treatment of 72ºC (161°F) for 15 sec (HTST) or 63ºC (145°F) for 30 min (or equivalent) does not kill all vegetative bacterial cells or spores ( Bacillus spp. and Clostridium spp.) Pasteurization temperature is continuously recorded Pasteurization

9. Pasteurization  is a process of heating a food, which is usually a liquid(milk), to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat.  This process slows spoilage caused by microbial growth in the food. Pasteurization- Defination

10. The French scientist  Louis Pasteur  invented pasteurization. To remedy the frequent acidity of the local wines he found out experimentally that it is sufficient to heat a young wine to only about 50–60 °C (122–140 °F) for a brief time to kill the microbes. Pasteurization was originally used as a way of preventing wine and beer from souring, and it would be many years before milk was pasteurized. Pasteurization of milk was suggested by  Franz von Soxhlet  in 1886. History of pasteurization

11.   Franz von Soxhlet and Louis Pasteur

12. Types of Pasteurization

13. Temperature of about 63ºc(145ºF) maintained for 30 minutes is called holding method (or) LTLT method Low Temperature Long Time(LTLT)/Holding Method

14. This involves following steps. Milk is pumped through a stainless steel heat-exchanger ↓ passes across one side of a series of plates which are in contact with hot water on the other side ↓ Milk emerges from the heat exchanger and passes into a stirred tank Holder process pasteurization

15. ↓ It is held for 30 min at 65ºc ↓ This tank is preferably fitted with a temperature recorder clamped to a clock to ensure that the temperature is maintained long enough to destroy the bacteria ↓ At the end of the 30 min. the milk is run out over a surface cooler or through another heat- exchanges in which cold water is run countercurrent to the milk on reverse side of the plates

16. The HTST pasteurization standard was designed to achieve a five-log reduction, killing 99.999% of the number of viable micro-organisms in milk. This method requires that the milk be held at 161 degrees for 16 seconds. This process, also refereed to as continuous flow pasteurization, requires the milk to be forced through metal pipes that are heated from the outside. HTST

17. This involves following steps raw milk ↓ Regenerator (heated) ↓ Flow access the other side of the heat exchanger plates ↓ The milk is raised to pasteurizing temperature HTST Method

18. ↓ passes through the heater unit and remains at this temperature for the time it takes to flow through holding tubes ↓ It is then cooled first by passing through the regenerator and then through the cooler

19. It produces a product that has a stable shelf life of up to two months.  UHT processing holds the milk at a temperature of 138°C (280°F) for a minimum of two seconds. After treatment it can pass through a heat-exchanger or by direct ingestion of live steam so called tetra pack process. UHT

20. Vat Pasteurization is the most gentle type of pasteurization. The milk is held in a heated vat at 145 degrees for 30 minutes. It is then quickly cooled to 39 degrees. VAT

21. Sterilization

22. Sterilization  is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents (such as fungi, bacteria, viruses, spore forms, etc.) present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media. Sterilization can be achieved by applying heat, chemicals, irradiation,high pressure, and filtration or combinations thereof. *Sterilization

23. Tyndalization Named after  John Tyndall  is a lengthy process designed to reduce the level of activity of speculating bacteria that are left by a simple boiling water method. It involves boiling for a period (typically 20 minutes) at atmospheric pressure, cooling, incubating for a day, boiling, cooling, incubating for a day, boiling, cooling, incubating for a day, and finally boiling again. The three incubation periods are to allow heat-resistant spores surviving the previous boiling period to germinate to form the heat-sensitive vegetative (growing) stage, which can be killed by the next boiling step. This is effective because many spores are stimulated to grow by the heat shock. The procedure only works for media that can support bacterial growth - it will not sterilize plain water .

24. Boiling milk or heating in flowing steam destroys all microorganisms except spores of bacteria and changes the appearance, palatability, digestibility, and nutritive properties of milk. BOILING

25. Evaporated milk is canned and then heat processed by steam under pressure. Often with accompanying rolling or agitation. The fore warming of milk at about 93-100ºc or higher before evaporation kills all but the more resistant bacterial spores. Sealed cans of evaporated milk are processed at 115ºc-118ºc for 14-18 min, which results in a commercially sterile product. STEAM UNDER PRESSURE

26. A Raw milk for pasteurization should be cooled at 10ºc or less within 2 hr after being drawn and kept that cold until processed. Newly pasteurized milk is to be cooled to 7.2ºc or less and maintained there. It is preferable, of course, to cool it to temperatures well below 7º-10ºc. REFRIGERATED STORAGE

27. Butter in storage is held at -17º to -18ºc or lower, where no microbial growth can take place. Frozen cream is stored in considerable amounts at a similar temperature. FREEZING

28. Microfiltration is the process of filtration with a micrometre sized filter. Microfiltration  is a membrane technical filtration process which removes contaminants from a fluid by passage through a microporous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometres (µm). Membrane filtration(microfiltration)

29. Dehydration of milk

30. Dehydrated milk is manufactured dairy product made by evaporating milk to dryness. Purpose - to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Dry milk is also easy to transport. First invented by Russian physician Osip Krichevsky in 1802. Commercially available in 1832 by Russian chemist M. Dirchoff.

31. Evaporated milk is made by removing about 60% of the water from whole milk, so that about 11.5% lactose would be in solution plus twice the amount of soluble inorganic salts in whole water. This high concentration of sugar is inhibitory to growth of some bacteria. Condensed milk is more concentrated than evaporated milk and is still a poor culture medium for organisms not tolerant of high sugar concentrations. CONDENSED PRODUCTS

32. used in the manufacture of infant formula, confectionery such as chocolate and in recipes for baked goods where adding liquid milk would render the product too thin. used in various sweets such as the famous Indian milk balls known as Rasgulla  and popular Indian sweet delicacy. common item in UN food aid supplies, fallout shelters and is favored by survivalists, hikers, and others requiring nonperishable, easy-to-prepare food. Reconstruction-one cup of potable fluid milk from powdered milk requires one cup of potable water and one-third cup of powdered milk. Uses This is the original container from 1947, provided by the Ministry of Food in London, England

33. Condensed milk is cow's milk from which water has been removed. It is most often found in the form of sweetened condensed milk, with sugar added. Sweetened condensed milk is a very thick, sweet product which when canned can last for years without refrigeration if unopened.

34. Raw milk is clarified and standardised, and then is heated to 85-90°C for several seconds. This heating destroys some microorganisms, decreases fat separation and inhibits oxidation. Some water is evaporated from the milk and sugar is added to approximately 45%. This sugar extends the shelf life of sweetened condensed milk. Sucrose increases the liquid's osmotic pressure, which prevents microorganism growth. The sweetened evaporated milk is cooled and lactose crystallization is induced. Production

35. sweetened condensed milk is the preferred milk to be added to coffee or tea. Many countries in Southeast Asia, use condensed milk to flavor their coffee. A popular treat in Asia is to put condensed milk on toast and eat it in a similar way as jam and toast. Condensed milk is an alternative to jam. It is a major ingredient in many Indian desserts and sweets. While most Indians start with normal milk to reduce and sweeten it, packaged condensed milk has also become popular. Uses

36. The use of sorbic or propionic acid or one of their salts is permitted in cottage cheese, yogurt and some of the hard cheese and processed cheese. The addition of preservatives to cottage cheese and yogurt is to prevent growth of moulds on the surface of product and to extend its shelf-life. Added sugar acts as a preservative of sweetened condensed milk and also it reduced the moisture, there by making moisture unavailable to microorganisms. USE OF PRESERVATIVES

37. Sodium chloride or common salt is added in the manufacture of various kinds of cheese, but usually it is more of flavour or for controlling the growth of microorganisms during manufacturing and curing than for preservation of finished product. Carbonation of milk, butter, and ice cream has been tried as an aid in preservation but without much success. Cheese is smoked primarily for the addition of flavour, although the drying, especially of the rind chemical preservative from smoked may improve keeping quality.

38. Mold spoilage of cheese is delayed or prevented sorbic acid, propionic acid, sorbates or propionates are added or incorporated in the wrapper. The addition of hydrogenperoxide combined with a mild heat treatment has been used for pasteurization of milk for certain kinds of cheese (e.g. swiss and cheddar). Developed preservatives most fermented products are microbiologically more stable have a longer shelf-life than initial substrate. Fermented milk and cheese are preserved partly by developed acidity produced by the bacterial culture and therefore have a longer shelf-life than fluid milk

39. The enzymes proteinases, lipases, lactase, beat-galactosidase, rennin(chymosin), and fruit enzymes are used in milk product. At present 4 proteinases, bovine and porcine pepsins and acid proteinases of mucor michei and m.pusillus are regarded as suitable substitutes of rennet. Lipases cause considerable food spoilage through hydrolytic rancidity. The principal application of lipases is in cheese manufacture, particularly hard italian varieties. USE OF ENZYMES IN MILK PRODUCTS

40. Lactose is the most dominant carbohydrate in the milk. The presence of lactose in some food preparation is desirable to stabilize flavour, taste and texture and as a reducing agent to bring about mailard browning as a source of desired flavour and colour. Beat-galactosidase is widely distributed in plant, animal and microbial sources; only the enzymes from Aspergillus niger, Kluyveromyces lactis, K.fragilis and E.coli are commercially available.

41. Rennin, an enzyme secreted by the young calves, bring about the coagulation of the milk. Rennin act as a general proteolytic enzyme on all the protein components. When casein is precipitated by the action of rennet, the calcium is not released to the whey but remain attached to the casein therefore, cheese made with rennet is a much better source of calcium than cheese made by acid precipitation alone. Cottage cheese is often made by acid precipitation. Rennin (chymosin)

42. Bromelin, a proteolytic enzyme, from pineapple digests proteins hence changes the gelation to compounds that do not form gel. The enzyme bromelin clots the milk and digests the clot. All fruits contain some organic acids but not always in sufficient concentration to cause the curding of milk. Destroying of the enzymes before combining the fruit with milk prevents curdling caused by the enzyme action, by blanching or by using canned fruits. Fruit enzymes

43. Salting acts as an antiseptic, slows down the development of microorganisms, improves the storage life of the cheese and speeds up the drying process and the formation of a rind.

44. ●Curd(dahi) ●Buttermilk ●Butter ●Ghee ●Evaporated milk ●Condensed milk ●Toned milk ●Dry milk ●cheese Milk products

45. Cheese Cheese is a food derived from milk that is produced in a wide range of flavors, textures, and forms by coagulation of the milk protein casein . It comprises proteins and fat from milk , usually the milk of cows , buffalo , goats , or sheep . During production, the milk is usually acidified, and adding the enzyme rennet causes coagulation. Milk products

46. Fresh cheeses  Fresh or unripened cheeses are coagulated under the action of lactic acid fermentation in the milk instead of adding rennet. While they are drained after formation of the curd, they are neither ripened nor fermented. This category includes cottage cheese, ricotta, mascarpone, cream cheese and quark. Fresh cheeses are mainly used in baking and desserts, plain or flavored with vegetables, fruits, herbs or spices.

47. Soft cheeses  Soft cheeses are ripened for a relatively short period of time before being drained and turned into molds without being pressed or cooked. They have a moisture content of 50% to 60% and their fat content represents 20% to 26% of the cheese’s weight Blue-veined cheeses Blue-veined (or blue) cheeses are neither cooked nor pressed; the curd is inoculated with a species of blue-green mold, which is injected into the cheese by means of long needles.

48. Butter is a dairy product that consists of butterfat , milk proteins , and water. It's made by churning fresh or fermented cream or milk . It is used as a spread and a condiment —and in cooking , such as baking, sauce making, and pan frying . Commonly made from cows ' milk, butter can also be manufactured from the milk of other mammals , including sheep , goats , buffalo , and yaks . Producers sometimes add Salt , flavorings , or preservatives . Butter

49. PRODUCT TEMPERATURE (℃) RH (%) SHELF LIFE CHEESE Blue 0-1.1 70 3-6 months Cheddar 0-1.1 70 12 months Cream 0-1.1 70 4 weeks Pasteurized 0-4.4 6-10 months Swiss 0-4.4 70 8-12 months MILK Evaporated +1 year Condensed 4.4 6-12 months 10 Few months 21.1 Few weeks HTST 2-3 weeks STORAGE CONDITIONS AND SHELF LIFE OF DAIRY PRODUCTS

50. PRODUCT TEMPERATURE (℃) RH (%) SHELF LIFE HTST 1.6-4.4 2-3 weeks 1.4-7.2 1-2 weeks UHT 1.6-4.4 +1 months Non-fat dry milk 4.4 60 10 months 21.1 60 5 months 37.7 60 2 months STORAGE CONDITIONS AND SHELF LIFE OF DAIRY PRODUCTS

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