The slides contain a brief introduction about Dairy Microbiology and information regarding Milk products and their production.

1. DAIRY MICROBIOLOGY

3. DAIRY : MILK
Milk is extremely perishable and many means have been developed
to preserve it. The earliest one which has been used for many thousands of
years is fermentation. Milk can be fermented by inoculating fresh milk with
the appropriate bacteria and keeping it at a temperature which favors
bacterial growth. As the bacteria grow, they convert milk sugar (lactose) to
lactic acid. You can detect its presence by the tart or sour taste (sour is
how we taste acid). The lowered pH caused by lactic acid preserves the
milk by preventing the growth of putrefactive and/or pathogenic bacteria
which do not grow well in acid conditions.
Milk contains components that are essential to humans such as
proteins, carbohydrates, fat, water, all the B-vitamins, vitamins A and D,
calcium and phosphorus. It also provides energy.
An important protein in milk is casein (in many cases 80% of the
milk protein). This is the base for cheese making. Casein is linked to
calcium phosphate, which is why milk contains a relatively large amount of
this salt that is a very important nutrient for humans and animals.
87% water
13% solids

5. Types of Milk
• Whole Milk (3.25% fat) contains 150 calories and 8 grams
(g) of fat per serving (8 fluid oz). Although not required,
whole milk may be fortified with vitamin D at a level of 400
International Units (IU) per 1 quart. If vitamin D is added,
the label must state this fact.
• 2% Reduced-Fat Milk (2% fat) contains 120 calories and
5 grams (g) of fat per serving(8 fluid oz). Vitamins A and D
are removed with the milk fat. For this reason, these
vitamins must be added to 2% reduced-fat milk so that it
contains at least 2,000 IU of vitamin A and 400 IU of
vitamin D per 1 quart. The addition of these vitamins must
be stated on the label.

6. • 1% Lowfat Milk (also called Light Milk) (1% fat) contains 100
calories and 2.5 grams (g) of fat per serving (8 fluid oz).
Vitamins A and D must be added to a level of at least 2,000 IU of
vitamin A and 400 IU of vitamin D per 1quart. The label must
indicate the addition of these vitamins.
• Fat-Free Milk (also called Skim or Nonfat Milk) (0% fat)
contains 80 calories and 0 grams (g) of fat per serving (8 fluid
oz). Vitamins A and D must be added to a level of at least 2,000
IU of vitamin A and 400 IU of vitamin D per 1quart The label
must indicate the addition of these vitamins.
• Chocolate Milk (fat-free,1% lowfat, 2% reduced-fat, whole
milk) is milk to which chocolate or cocoa and a sweetener have
been added. This milk is just as nutritious as its unflavored
counterpart. Compared to plain milk, chocolate milk contains
about 60 more calories per serving (8 fluid oz).

7. • Evaporated Milk
(6.5% fat) is made by removing about 60% of the water
from whole milk. The milk is then homogenized, fortified
with vitamin D to a level of 25 IU per 1fluid ounce, canned
and heat sterilized. The addition of vitamin A is optional. If
added, each fluid ounce must contain not less than 125 IU
of vitamin A.
Evaporated Fat-Free Milk (0.5% fat or less) is a
concentrated, fortified (vitamins A and D) fat-free (skim or
nonfat) milk that is canned and sterilized
Sweetened Condensed Milk (8% fat or less) is a canned
milk concentrate of whole milk to which sugar has been
added. The sweetener used (usually
sucrose) prevents spoilage. Sweetened condensed fat-free
milk contains no more than 0.5% milk fat.

10. Buttermilk
Buttermilk refers to a number of dairy drinks. Originally, buttermilk was
the liquid left behind after churning butter out of cream. This type of
buttermilk is known as traditional buttermilk.
The term buttermilk also refers to a range of fermented milk drinks,
common in warm climates (e.g., the Balkans, the Middle East, Turkey,
Afghanistan, Pakistan, India, Sri Lanka and the Southern United States)
where unrefrigerated fresh milk sours quickly, as well as in colder climates,
such as Scandinavia, Finland, Ireland, Netherlands, Germany, Poland,
Slovakia and Czech Republic. This fermented dairy product known
as cultured buttermilk is produced from cow's milk and has a
characteristically sour taste caused by lactic acid bacteria. This variant is
made using one of two species of bacteria—either Lactococcus
lactis or Lactobacillus bulgaricus, which creates more tartness.

11. The tartness of buttermilk is due to
acid in the milk. The increased acidity is
primarily due to lactic acid produced by lactic
acid bacteria while fermenting lactose, the
primary sugar in milk. As the bacteria
produce lactic acid, the pH of the milk
decreases and casein, the primary milk
protein, precipitates, causing
the curdling or clabbering of milk. This
process makes buttermilk thicker than plain
milk. While both traditional and cultured
buttermilk contain lactic acid, traditional
buttermilk tends to be less viscous, whereas
cultured buttermilk is more viscous.
Buttermilk can be drunk straight, and
it can also be used in cooking. Soda bread is a
bread in which buttermilk reacts with the
rising agent, sodium bicarbonate, to
produce carbon dioxide.

12. Cultured Sour Cream
• Sour Cream (cultured sour cream) is
the product resulting from adding lactic
acid bacteria to pasteurized cream at
least 18% milk fat.
• Acidified Sour Cream results from
souring pasteurized cream with safe and
suitable acidifiers, with or without lactic
acid-producing bacteria. One tablespoon
of sour cream contains about 26 calories
and 2.5 grams (g)
of fat.
• Reduced-Fat Sour Cream and Acidified
Sour Cream contain at least 25% less fat
per serving than a serving (2
tablespoons) of sour cream or acidified
sour cream, respectively. Reduced-fat
sour cream contains 20 calories and 1.8
grams (g) of fat per tablespoon.

13. Bulgarian milk
Bulgarian milk refers to a fermented
milk product obtained with Bulgarian
symbiotic starter from L.bulgaricus and
S.thermophilus by an original technology
without any additives.
Heat the fresh (skimmed) milk to boiling
point, stirring all the time. Cool it down to 18 –
20°C, for instance in a large pan with cold water.
Add 10 – 30 ml of sour milk or buttermilk or a
starter culture per each litre of milk (1%). Leave
for it 18 - 24 hours at room temperature (18 –
20°C); if the surrounding temperature is higher,
fermentation time will be somewhat shorter. After
this the milk is ready. Store it in a cold place (cool
basement or a refrigerator), if you want to keep it
for some days.

14. Acidophilus milk
Acidified buttermilk is a related product made by adding a food-grade acid (such as
lemon juice) to milk. It can be produced by mixing 1 tablespoon of vinegar or
lemon juice with 1 cup of milk and letting it sit until it curdles, about 10 minutes.
Any level of fat content for the milk ingredient may be used, but whole milk is
usually used for baking. In the process which is used to produce paneer such
acidification is done in the presence of heat.

16. Yoghurt is produced when milk is
soured by certain lactic acid bacteria, which
prefer growing temperatures far above room
temperature: 37 – 45°C. The milk should first
be heated to 85°C or higher. A high
pasteurisation temperature (above 72°C)
gives a better consistency (thickness) to the
final product. After the milk has been soured,
the resulting yoghurt can be used to make
more fresh yoghurt by adding it to fresh milk.
Heat the milk to 85°C or higher and
keep it at this temperature for 3 minutes. Cool
the milk to 45°C. Add 30 ml (2 - 3 tablespoons)
of fresh yoghurt to each litre of milk; the
yoghurt should not be more than 2 days old.
Instead of fresh yoghurt you can use a yoghurt
starter culture. Mix the milk and the starter
and leave it to ferment. The time required for
the milk to turn sour depends on the
temperature.

17. The Lactobacillus bulgaricus bring
acidity to the milk.
The Streptococcus thermophilus
develop aroma

18. Yogurt Nutrition
Nonfat Yogurt/1 cup
Calories 100
Total fat (g) 0
Saturated fat (g) 0
Monounsaturated fat (g) 0
Polyunsaturated fat (g) 0
Dietary fiber (g) 0
Protein (g) 10
Carbohydrate (g) 19
Cholesterol (mg) 5
Sodium (mg) 135
Calcium (mg) 300
Low-fat Yogurt/1 cup
Calories 155
Total fat (g) 3.8
Saturated fat (g) 2.5
Monounsaturated fat (g) 1
Polyunsaturated fat (g) 0.1
Dietary fiber (g) 0
Protein (g) 13
Carbohydrate (g) 17
Cholesterol (mg) 15
Sodium (mg) 172
Riboflavin (mg) 0.5
Vitamin B12 (mcg) 1.4
Calcium (mg) 448
Phosphorus (mg) 353
Potassium (mg) 573
Zinc (mg) 2.2

19. Types of Yogurt
Set Yogurt- this type of
yogurt is incubated and
cooled in the final
package. Firm “jelly
like” texture.
Stirred Yogurt- incubated
in a tank and final
coagulum is broken by
stirring before cooling. Less
firm then set yogurt (like a
thick cream). A little
reformation of coagulum
will occur after packaging.
Drinking Yogurt-also
has coagulum
broken before
cooling. Very little
reformation of
coagulum will occur.

20. Types of Yogurt (continued)
Frozen Yogurt- Incubated
like stirred yogurt.
Cooling is achieved by
pumping through a
freezer like ice cream.
Has a texture like ice
cream.
Concentrated Yogurt-incubated
like stirred
yogurt. After coagulum
is broken, some water is
boiled off. Produces
rough and gritty
textures.
Flavored Yogurt-
Flavors are added
just before yogurt
is poured into pots.
Add in usually
contain about 50 %
sugar.
http://www.cip.ukcentre.com/yogurt.htm

21. 10 Reasons Yogurt is a Top Health Food…
1. Easier to digest then milk
2. Contributes to colon health
3. Increases the absorption of other nutrients such as calcium
4. Boosts immunity
5. Aids in healing process after infections in the intestines
6. Decreases yeast infections
7. A rich source of calcium
8. Good source of protein
9. Lowers cholesterol
10. It is a “grow food” meaning it helps children to grow

22. Kefir
Kefir, like yoghurt, is a milk product
first discovered by the nomadic tribes living
in the cold areas of the Caucasus. When
making kefir, acid, gas and some alcohol are
produced. Like sour milk and buttermilk, it
has a special aroma which is different from
that of yoghurt. Kefir is made by using a
'yoghurt plant', which is actually a misleading
name as it is not a plant and it has nothing to
do with yoghurt.
The 'yoghurt plant' is in fact a cauliflower-like
lump of chalky crystals and micro-organisms
consisting of yeasts and bacteria. The yeasts
produce alcohol and gas, while the bacteria
convert the milk sugar into lactic acid. You
may be able to obtain a piece of this from
someone who regularly makes kefir. If not,
get some dried kefir granules at the local
market.

23. Boil the milk and put it into a bottle,
which has been thoroughly cleaned and
rinsed with hot water. Do not fill the
bottle completely; let the milk cool down
to 20°C (use a thermometer). Add one
tablespoon of kefir granules soaked in
water to each half litre of milk in the
bottle and cover it loosely so that the gas
produced can escape. You can use a fresh
yoghurt plant instead of the soaked
granules. Keep the bottle at a
temperature of 16 to 18°C. After 24
hours the milk will have become a little
thicker, forming some froth: this is kefir.
Sieve the kefir and use the (washed with
clean water) granules, which remain in
the sieve to make fresh kefir again. The
kefir is now ready for consumption or
can ripen for some days to get more
flavour.

24. Ripening of the kefir
The kefir can be left to ‘ripen’, during which time further
fermentation takes place. This is essential to create kefir’s
characteristic qualities. Pour the kefir into a well-cleaned bottle,
which can be closed, or a bottle with a clip fastening and do not fill
more than 3/4 because gas forms during ripening.
Leave the bottle at about 15°C, but do not store it for more
than 3 days. Towards the end of the ripening process the whey
separates and can be incorporated again by stirring or turning the
bottle. The end product is a thick, creamy, frothy drink with a sour
taste and smell and the produced carbon dioxide is perceivable. If the
kefir is left to ripen for more than 3 days, the milk may curdle and the
drink becomes too sour. The temperature and the time are important
as they determine the flavour. The kefir can be kept in a refrigerator
or a cellar for a few days.

25. Koumiss
Koumiss is a sour milk product similar to Kefir. It is
manufactured from mare milk.
Koumiss often called "milk wine" or "milk brandy" as
it is a fermented drink of milk beralkhohol.The name of
koumiss obtained from asia tribes in ancient times, namely
kumanes or komans.
Traditional koumiss made from mare's milk from
grazing horse races kumanes that sustain life on the steppes
of Central Asia until 1235.
Koumiss fermentari result is a product of the
bacterium L.Bulgaricus and yeast talura alcohol producer.
Due to lack of milk production of koumiss horse is now often
made from cow's milk, but the milk has a composition that is
not the same.

27. Cheese
Cheese is a product made from curd obtained from the whole,
partly fat free/non-fat, or fat-free/non-fat milk of cows or from
milk of other animals, with or without added cream, by
coagulating with rennin, lactic acid or other suitable enzyme or
acid and with or without further treatment of the separated
curd by heat or pressure, or by means of ripening ferments,
special molds, or seasoning.

28. There is a huge assortment of cheeses. They can have
various compositions; we make a rough distinction between
fresh cheese and matured cheese, and between soft cheese and
hard cheese.
Fresh cheese can be consumed immediately after
production, whereas matured cheese has to be stored after
processing to develop flavour and a good consistency.
Soft cheese has a higher water content than hard cheese;
moreover hard (or semi-hard) cheese generally has a clean, dry
rind. Soft cheeses and hard cheeses can be matured for some
weeks or even up to a number of years.

29. Production
• Coagulation: enzyme or acid
• Curd treatment involves:
• Cutting: to increase surface area- to remove more whey
• Heating: to evaporate water, to destroy bacteria
• Salting: to dehydrate curd, to control bacterial growth,
flavor, texture
• Knitting: the use of heat to combine curd
• Pressing to create more solid mass before ripening
• Curing or ripening: exposure of cheese to controlled
temperature and humidity conditions to promote chemical
and physical changes in cheese.

35. Spoilage of Milk
Milk should be handled with care. There are several factors that can make milk go
off and become unsuitable for further consumption. These include:
The presence of too many micro-organisms in the milk
contamination by diseased animals (tuberculosis, brucellosis) and/or
people.
Bacterial and/or chemical conversion of certain substances in the
milk contamination of the milk with antibiotics (used for treatment of
diseased animals), disinfectants, pesticides and so on.