This presentation involves with the fermented products of dairy items and their manufacturing procedures. This presentation includes production of cheese, buttermilk, yoghurt, kefir and sour cream

1. FERMENTED DAIRY
PRODUCTS
M.J. AFRA
I MSC MICROBIOLOGY
TBAKC

2. DAIRY PRODUCTS
 Dairy products or milk products, also known as lacticinia, are food products made from (or
containing) milk
 The most common dairy animals are cow, water buffalo, nanny goat, and ewe.
 Dairy products include common grocery store food items in the Western world such
as yogurt, cheese, milk and butter
 A facility that produces dairy products is known as a dairy
 Dairy products are consumed worldwide to varying degrees
 Some people avoid some or all dairy products either because of lactose intolerance, veganism, or other
health reasons or beliefs.

3. CHEESE PRODUCTION

4. CHEESE PRODUCTION
 Cheese is made by coagulation or curdling the milk with acid or rennin or both, drawing off the whey
and processing the curd.
 Cheese is one of the by-products of the milk.
 It is processed form either cream of milk or cream and milk mixed together.
 It is very valuable food. It should not be over-cooked.
 It should always be combined with starchy foods, this aids the digestion.
 Low temperature and short cooking is recommended. Some cheeses are flavored with herbs or spices
 Keep in cool and dark place
 Wrapped in grease proof paper to prevent the drying Storing away from foods otherwise it will absorb
flavor of vegetables.
 If, it is kept at too cold temperature, it will dehydrate and if put in a warm place it will sweat

5. TYPES OF CHEESE
 Composition - moisture, fat content; Structure - texture and body; Flavour - salty, propionic, nutty..; Appearance -
colour, wax rind or size of the block; Starter Culture – S.thermophilus and L.bulgaricus
 Cheese can be thought as a means of preserving milk by removing water. Characteristics can be manipulated by
altering the cultures, ingredients and techniques used.
 There are five main types of cheeses used in the kitchen
1. Dry Salt Cheese (Cheddar, Colby)
2. Brine Salt Cheese (Gouda, Edam)
3. Stretched Curd (Mozzarella)
4. Specialty Cheeses (Blue Vein)
5. Processed Cheese

6. PROCESSING
 Raw Milk -> Standardisation -> Pasteurisation -> Curd Manufacture
 Standardize of proteins across the whole season (consistency)
 Fat level for different classes should be used
 Heat treatment at 72oC for 15 seconds
 Kills Majority of Microbes in Milk

7. MANUFACTURING
COW MILK
STANDARDIZA
TION
PASTEURIZATI
ON
COOLING
ADD STARTER
CULTURE
RENNETING
CUTTING OF
CURD
COOKING OF
CHEESE
DRAINING
OF WHEY
CHEDDARIN
G
PLASTICIZIN
G AND
MOULDING
CHILLING
PACKAGE
AND STORE

8. MANUFACTURE
1. RIPENING OF MILK
 Starter (lactic acid producing bacteria) added to the milk.
 Animal’s afternoon milk mixed with equal qty of fresh morning milk.
 Milk left overnight – starter develops
 Temperature of milk is controlled at 30OC
2. CURD MANUFACTURE STARTER
 “Beneficial” bacteria which ferment the sugar (lactose) in milk
 Different species of the bacteria impact cheese flavour.
 The Starter culture was added to the ripened milk inorder to ferment as curd

9. MANUFACTURE
3. RENNETING
Two sources of rennet enzymes:
 An enzyme which acts on protein and causes it to coagulate.
 There are two sources of rennet enzyme.
 Animal rennet is an enzyme which is extracted from the fourth stomach of calves
 Vegetable based rennet contains no animal products and has the same coagulating ability as animal rennet when
used in milk that has been ripened (acidified) by cheese starter bacteria. This rennet is available in tablet and
liquid form.
 Rennet must be diluted with distilled water prior to adding to milk.
 Rennet must be refrigerated.

10. MANUFACTURE
4. CUTTING AND COOKING OF CURDS
 Filling Vats (Cool To Approximately 30 OC)
 Starter Addition
 Coagulation Using Rennet Takes About 30 – 50 minutes
 Cutting Curds into 5mm by rotating knives
 Whey (liquid part) is separated from curd by De-whey/wash where whey taken off and remove lactose by
washing with potable water
 The curd was cooked at 38oC helps to expel moisture out of curd

11. MANUFACTURE
4. DRAINING OF WHEY
 The draining of whey done by two methods Dry Salt Process and Brine Salt Process
 For Dry Salt Cheese: Whey separated via screen -> Cheddaring on Alfomatic belt system -> Miling
 For Brine Salt Cheese: Whey removal and Block formers in Casomatic tower -> Cheese mould -> Pressing
5. CHEDDARING OF CHEESE
 Curd Loses More Moisture
 Clumps Together Into Continuous Mat
 In Approx. 2 Hours
 Acid Development To ≈ pH 5.3

12. MANUFACTURE
7. SALTING
 Mat of curd then milled into finger-sized pieces
 Salt applied and mixed
 Dry Salt Cheese (1.6 – 2.0%)
 Brine Salt Cheese (Soaked In Brine Tank For 24 – 72 hours)
8. PLASTICIZING
 A method of processing cheese which consists in adding to cheese a small amount of an edible dibasic salt of citric acid, heating the mass to
a temperature that is sufficiently high to effect pasteurization but not sufficiently high 'to disintegrate the cheese, and then pouring the
cheese in containers
 Plasticizing of cheese curd is an important step in the manufacture of Mozzarella cheese.
 Plasticizing of curd affects the cheese composition which directly influences the properties of cheese by controlling the microbial activity,
enzyme activity, texture and even baking characteristics

13. MANUFACTURE
9. COLORING AND MOULDING
 2% Salt is added. Annatto (wild berry which gives yellow color) is added.
 Moulding in different iron moulds-young/green/cottage cheese
 Note- hydraulic pressure can be applied after moulding to remove the remaining whey.
10. MATURING OR RIPENING
 Temp. Controlled at 140OC. The ripening is basically about the breakdown of proteins, lipids, carbohydrates which releases the flavour
compounds and modifies cheese
 It varies from nil for fresh cheese to 5 years for some hard ripened cheese
 Moulded curd is covered with cheese cloth.
 Mold grows on cheese cloth and gives color and flavor.
 Molds penicillium glaucum (white) and penicillium roqreforti (blue).

14. MANUFACTURE
11. STORAGE AND PACKAGING
 Blocks put into plastic bags, vacuum sealed and put into boxes
 Dry-salt cheese passes through a rapid cool room (~ 24 hours)
 Metal detector, coding, then palletised
 Temperature and time will depend on the type of cheese (e.g. cheddar 10°C until mature)

15. YOGHURT PRODUCTION

16. PRODUCTION OF YOGHURT
 Yogurt, often known as yoghurt, is one of the most popular fermented dairy products in the world, with a wide range of
health advantages in addition to basic nutrition.
 In general, yogurt is a nutrient-dense food because of its nutritional profile, and it is a high-calcium source that supplies
considerable amounts of calcium in bio-available form.
 Furthermore, it contains milk proteins with a higher biological value as well as nearly all of the essential amino acids
required for optimal health.
 Yogurt is a probiotic carrier food that may transfer large numbers of probiotic bacteria into the body, providing unique
health benefits if consumed.
 These are commonly referred to as "bio-yogurts."
 Yogurt is also said to help with lactose tolerance, immunological boosting, and the prevention of gastrointestinal
problems.

17. CLASSIFICATION OF YOGHURT
1. Firm
2. Powdered
3. Stirred
4. Concentrated
5. Drinking
6. Frozen

18. MICROBIAL CHARACTERISTICS
 S.thermophilus and L. Delbrueckii subp. Bulgaricus are two
thermophilic lactic acid bacteria that cause yoghurt fermentation.
 They are gram-positive, anaerobic, aerotolerant, and catalase-negative,
with no spores and a DNA concentration of less than 55 percent G+C.
 They can grow between 42 and 500 degrees Celsius, but not above 100
degrees Celsius.
 L. Delbrueckii subsp. Bulgaricus develops as ovoit cells, whereas S.
thermophilus forms linear chains of rods.
 They convert lactose to galactose, which is not metabolized, and
glucose, which is primarily fermented to lactic acid, resulting in homo-
fermentative metabolism.

19. CHANGES DURING LACTIC ACID
FERMENTATION
 The growth of lactic acid bacteria in milk causes
several modifications in yoghurt that are
favorable.
 The formation of several metabolites (lactic acid,
exopolysaccharides, and fragrance compounds),
as well as the altering of the texture and
nutritional content of the product, are among
these changes

20. FLAVOUR COMPOUND PRODUCTION
 Due to the presence of lactic acid in the product, the flavor of yoghurt is mostly acidic.
 About a hundred volatile chemicals make up the scent of yoghurt, including carbonyl
compounds (acids and esters), alcohols, heterocyclic, and sulphur-containing compounds.
 Acetaldehyde is the most important flavor ingredient in yoghurt, where it imparts a pleasant
fresh and fruity scent.
 The majority of acetaldehyde is made directly from pyruvate via pyruvate decorbxylase or
indirectly using acetyle coenzyme

21. PREPARATION
Standardizing Homogenizing Pasteurizing Cooling
Addition of
starter culture
Incubation
Cooling
Stirring
Packaging
And Cooling

22. PREPARATION
MILK STANDARDIZATION
 Standardization of fat and protein levels, as well as the addition of sweeteners and stabilizers, are all part of the milk
production process.
 Milk standardization is carried out at 550°C, with additional fat content removed using a centrifugal technique.
 Nonfat yoghurt has a fat content of 0.01 percent, light fat yoghurt has a fat content of 1-2 percent, and whole fat yoghurt has a
fat content of >3.2 percent.
 To improve the smoothness of the yoghurt and reduce syneresis, the protein level of the mix can range from 3-5 percent to up
to 15%.
 The most common method is to add milk powder, which is a simpler and more traditional method.
 Milk proteins are commonly used as caseinates/whey powder.
 FAO/WHO allows the use of thickeners and stabilizers (gelatine, pectin, xanthan gum, carrageen an, starch, etc.) at quantities
ranging from 5-10% to improve the texture of yoghurt in some countries

23. PREPARATION
FERMENTATION PROCESS:
 Heat treatment is an important part of the mixing process.
 Heat treatment permits spoilage microorganisms and inactive lactoperoxidises in milk to be removed.
 Heat treatment enhances the texture of yoghurt by permitting whey protein denaturation and interaction with casein, which
reduces gel syneresis and increases gel hardness.
 The combination is normally heated at 90-950C for 3-7 minutes before cooling down to fermentation temperature in
industrial yoghurt manufacturing.
 Heat treatment is intimately linked to two additional physical treatments: mix dearation and homogenization.
 Before homogenization, vacuum dearation is usually done at 700C.
 The mix is homogenized at a high pressure (20-25 MPa) at a temperature near 700C.
 For high fat yoghurt, double stage high pressure homogenizers are advised

24. PREPARATION
INOCULATION OF MIX
 Yogurt is made on a large scale by inoculating a mix with concentrated starter cultures of the two yoghurt
bacteria (S. Thermophilus and L. delbrueckii subsp. Bulgaricus).
 Commercial starter cultures are made up of precise blends of well-defined strains with a concentration
more than 1010 colony-forming units (CFU)g 1, and are frozen or freeze-dried formulations.
 The bacteria in the injected mix are usually 106–107 CFU ml
 After mixing, it is either transported to the fermentation tanks (for the production of stirred, sipping, or
concentrated yogurt) or immediately to the packaging machine (for the production of fermented yogurt in
cups) (for set-type yogurt manufacture).

25. PREPARATION
FERMENTATION STEPS
 Several characteristics change as time passes during the lactic acid fermentation of milk.
 S. thermophilus is the first to grow, followed by L. delbrueckii subsp. bulgaricus, with final concentrations approaching 109
CFU g
 Lactose and nitrogenous substances are consumed by both strains, allowing them to thrive and accumulate a variety of
important metabolites.
 The most important ones are lactic acid, galactose, acetaldehyde, and exopolysaccharides, which contribute to the yogurt's
flavor and texture.
 The production of extracellular lactic acid causes an acidification of the mixture, resulting in a pH drop from 4.8 to 4.5.
 Fermentation culture was added in a concentration of around 2%.
 The fermentation process might take anything from 3 to 20 hours.

26. KEFIR PRODUCTION

27. PRODUCTION OF KEFIR
 Kefir is a viscous, slightly carbonated dairy beverage that contains small quantities of alcohol and, like yoghurt, is believed
to have its origins in the
 Caucasian mountains of the former USSR.
 It is also manufactured under a variety of names including kephir, kiaphur, kefer, knapon, kepi and kippi with artisanal
production of kefir occurring in countries as widespread as Argentina, Taiwan, Portugal, Turkey and France.
 It is not clear whether all kefirs originate from a single original starter culture, since microbial analyses of kefir samples
taken from different locations indicate microflora population differences.
 Although no clear definition of kefir exists, it is a viscous, acidic, and mildly alcoholic milk beverage produced by
fermentation of milk with a kefir grain as the starter culture (FAO/WHO 2003).
 The Codex Alimentarius description of kefir state it as Starter culture prepared from kefir grains, Lactobacillus kefir, and
species of the genera Leuconostoc, Lactococcus and Acetobacter growing in a strong specific relationship.
 Kefir grains constitute both lactose-fermenting yeasts (Kluyveromyces marxianus) and non-lactose-fermenting yeasts
(Saccharomyces unisporus, Saccharomyces cerevisiae and Saccharomyces exiguus)

28. MANUFACTURE
 Although commercial kefir is traditionally manufactured from cow’s milk, it has also been made from the
milk of ewes, goats and buffalos.
 Moreover, kefir produced using soy milk has also been recently reported.
 Traditionally, kefir is produced by adding kefir grains (a mass of proteins, polysaccharides, mesophilic,
homofermentative and heterofermentative lactic acid streptocci, thermophilic and mesophilic lactobacilli,
acetic acid bacteria, and yeast) to a quantity of milk.
 The size of the initial kefir grain inoculum affects the pH, viscosity and microbiological profile of the
final product.
 A grain to milk ratios of 1:30 to 1:50 were found optimum.

29. MANUFACTURE
 In some manufacturing procedures, a percolate of the grains from a coarse sieve is used as the mother culture to inoculate
fresh milk.
 Fermentation of the milk by the inoculum proceeds for approximately 24 hours, during which time homofermentative
lactic acid streptococci grow rapidly, initially causing a drop in pH.
 This low pH favours the growth of lactobacilli, but causes the streptococci numbers to decline.
 The presence of yeasts in the mixture, together with fermentation temperature (21-23°C), encourages the growth of aroma
producing heterofermentative streptococci.
 As fermentation proceeds, growth of lactic acid bacteria is favoured over growth of yeasts and acetic acid bacteria.
 Kefir grains are key to kefir production, and it has been found that the finished product has a different microbiological
profile from the grains and therefore cannot be used to inoculate a new batch of milk.
 Grains have been shown to possess a dynamic and complex flora which is not conducive to commercial production of a
uniform, stable product; this has prompted researchers to try to produce kefir from a mixture of pure cultures.

30. MANUFACTURE
Raw Milk Standardisation Homogenisation Pasteurization Cooling
Addition of
kefir grains
Incubation
Removal of
kefir grains
Packing and
cold storage

31. KEFIR GRAINS
 Kefir grains resemble small cauliflower florets: they measure 1-3 cm in length, are lobed, irregularly shaped, white to
yellow-white in colour, and have a slimy but firm texture.
 Grains are kept viable by transferring them daily into fresh milk and allowing them to grow for approximately 20
hours; during this time, the grains will have increased their mass by 25%.
 Grains must be replicated in this way to retain their viability, since old and dried kefir grains have little or no ability to
replicate.
 In addition, washing grains in water also reduced viability.
 It has been recommended that in a commercial operation using grains to produce kefir, grains should be kept viable
through daily transfers and should only be replaced if their ability to ferment milk becomes impaired.
 Low temperature storage appears to be the best way to maintain kefir grains for long periods.
 Storage of kefir grains at 80° or 20°C for 120 days did not change their fermentation properties compared to grains that
had not been stored; however, grains stored at 4°C did not produce acceptable kefir after thawing.

32. SOUR CREAM
PRODUCTION

33. PRODUCTION OF SOUR CREAM
 Sour cream is cultured or acidified light cream.
 Cultured sour cream, which is the more common type, is soured and thickened by adding lactic acid bacteria to pasteurized cream with at
least 18 percent milkfat.
 Acidified sour cream is soured and thickened by the direct addition of an acid, such as vinegar, instead of a fermentation process.
 Early versions of sour cream were created when fresh milk was left to sit at room temperature and the cream rose to the surface. Naturally
occurring bacteria soured it.
 Sour cream is prominent in central and eastern Europe, where it has traditionally been added to soups and stews (goulash, borscht).
 Immigrants brought it to America where it has become a base for dips and salad dressings, a topping for baked potatoes and for use in
baking.
 Souring of cream when producing sour cream butter is usually done with cultures of Streptococcus diacetilactis, Streptococcus
cremoris and Leuconostoc citrovorum.
 Cultures can be used deep frozen, freeze dried or multiplied in a mother culture. The optimal temperature to multiply mother cultures for
buttering lies between 25 and 30°C.

34. PRODUCTION OF SOUR CREAM
 The maximum acidity achievable is ∼1%.
 The base material for such mother cultures is skim milk, which is heat-
treated, cooled, inoculated with the original culture and subsequently
fermented.
 Ripening of the culture is stopped by cooling.
 Soured milk for buttering is prepared by inoculation from this stock
 The amount of souring culture as well as the cooling temperature, the
souring temperature and the ripening temperature depend on the hardness
of the milk fat, which is proportional to the iodine value

35. MANUFACTURE
 Cultured sour cream is made by adding a culture of Streptococcus lactis to pasteurized light cream and
incubating at 72˚F until the desired flavor and thickness is reached.
 The lactic acid produced by the culture coagulates the protein, thickening the cream and adding the
characteristically sour flavour. Non fat milk solids and stabilizers may also be added.
 The milkfat content of sour cream products depends on the milkfat content of the milk or cream from which
they are made.
 Store sour cream in its closed container in the refrigerator, which is typically set at 38˚F-40˚F.
 If separation occurs, gently stir the liquid back into the sour cream.
 If any mold forms on the cream’s surface, discard it immediately

36. BUTTERMILK
PRODUCTION

37. PRODUCTION OF BUTTERMILK
 Drinking of butter after churning dahi in to country butter is a very common habit in India.
 This product has most of the fermented milk solids except fat which goes in butter.
 It also has mixed lactic acid bacteria, especially Lactococci and Leucostocs,which gives it a typical diacetyl
flavour.
 Manufacturing cultured butter milk on industrial scale involve selection of good quality raw material standard
cultures and optimized process of fermentation, packaging and storage.
 True buttermilk is the fluid remaining after cream is churned into butter.
 If butter is made from sweet cream, its buttermilk has approximately the same composition as skim milk.
 Cultured butter milk is prepared by souring true butter milk or more commonly, skim milk with a butter starter
culture that produces a desirable flavor
 Cultured butter milk is prepared with the help of normal mesophilic lactic acid bacteria.
 There should be satisfactory balance between acid and flavor producers in the starter and aroma.

38. PREPARATION
SELECTION OF MILK
 The quality of raw material decides the quality of final product.
 The raw milk selected for CBM manufacture should normal composition, be free
from off flavor and odours and free from inhibitory substances.
 It should have lower microbial count.
STANDARDIZATION OF MILK
 It is usual practice to standardize milk for fat and solids-not-fat content looking to
legal requirements and also as per consumer demands.
 Generally skim milk is the starting material and it may be added with approximately
1.7% fat.
 In certain commercial processes, fat is added as granules in cold fermented butter
milk.
 Sodium chloride at the rate of 0.1 – 0.2% and sodium citrate at the rate of 0.1 –
0.2% may be added for enhancement offlavor

39. PREPARATION
HEAT TREATMENT
 Proper heat treatment of at least pasteurization equivalence is mandatory for CBM production.
 This is to ensure destruction of pathogens and make the product safe for human consumption.
 It also helps in proving suitable environment for the cultures.
 Based on earlier experiences and scientific evidences, it found that heating at 85° for 30 min is the optimum heat
treatment for CMP production which gives best quality product in terms of flavour and shelf-life.
 Heating below 82°C or above 88°C causes a weak body, that allows whey separation in cultured butter milk.
COOLING
 Milk must be cooled down to inoculation temperature as soon as holding period is over.
 Inoculation in hot milk will destroy the culture. It should be 22-25°C for cultured buttermilk.

40. PREPARATION
INOCULATION
 The milk should be inoculated with appropriate mesophilic starter culture just after cooling. Inoculation rate varies from 0.5 to 2.0%,
depending upon the starter activity and time of incubation
 At the time of inoculation,starter should have 0.80-0.85% acidity.
 Over ripe culture are not suitable as the lactic streptococci have passed their peak of acidity. If it is under ripenedi.e. less than 0.8% lactic acid,
it will not have sufficient number of aroma bacteria.
INCUBATION
 The typical incubation temperature for CBM is 21.6°C. There are several reasons for selecting 21-22°C as incubation temperature.
 Any departure of more than a degree or two above or below will cause imbalance in the bacterial mixture and will adversely affect the
product.
 At lower temperature, the starter organisms grow too slowly, and curdling is delayed excessively. At much higher temperature, the
streptococci overgrow aroma bacteria and product lack flavor and aroma. At higher incubation temperature the curd forms at a lower acidity
and it tends to shrink, causing whey separation.
 Use of lowest practicable temperature inhibits the growth of undesirable bacteria that survive the heat treatment given to the milk.

41. PREPARATION
COOLING, AGITATION AND DILUTION
 After desired stage of ripening, the curd must be cooled rapidly to avoid over ripening. Mixing may be necessary to hasten cooling, but it should not
be done in a manner that incorporate air.
 Excessive agitation decreases the stability of butter milk and increases whey separation. Gentle agitation is required to break curd and to have efficient
and quick cooling.
 At the stage dilution of the product may also may be done to adjust solids level to desired level.
 Some manufacturers also add some spices and condiments to flavour it. The final cooling of the product should be to less than 5°C.
PACKAGING & STORAGE
 Bottle or cartons packaging material are commonly used. Packaging material should not excessively increase the microbial load in the product.
 Product will have better shelf-life if stored below 5°C

42. THANK YOU
M.J. AFRA