The document discusses the role of microorganisms in milk fermentation. It describes the composition of milk, including the varying percentages of milk fat, lactose, and milk protein in different mammals. It then focuses on the microorganisms involved in milk fermentation, particularly lactic acid bacteria which are important in the fermentation process. Starter cultures including various lactic acid bacteria are used to control and standardize fermentation. Fermentation provides benefits like food preservation, safety enhancement, and nutritional value improvement.

1. ROLE OF MICROBIOLOGY IN MILK
FERMENTATION
Presented By
Amit Kumar

2. Composition of milk
• Milk fat
- Aquatic mammals typically have high milk fat percentage.
- The most variable component of milk
- it ranges from a little over 1%to greater than 50%.
• lactose
- range from only a trace to less than 7%
- Some from have very little lactose in milk , such as bear bear and kangaroo.
• Milk protein
- Ranges from 1% to about 14%.
- Generally milk protein percentage is positively correlated with milk fat
percentage .

3. Microorganisms in Milk
• Lactic acid bacteria
-This bacteria is important to milk fermentation.
The lactic acid bacteria are mesophiles:
– they generally grow over a temperature range of about 10 to 40oC,
– an optimum temp between 25 and 35oC.
– Some can grow below 5 and as high as 45 oC.
• Most can grow in the pH range from 4 to 8. Though some as low as 3.2
and as high as 9.6.

4. • Starter cultures
- Traditionally the fermenting organisms came from the
natural microflora or a portion of the previous fermentation.
- In many cases the natural microflora is either inefficient,
uncontrollable, and unpredictable, or is destroyed during
preparation of the sample prior to fermentation (eg
pasteurisation).
- A starter culture can provide particular characteristics in a
more controlled and predictable fermentation.

5. • Lactic starters always include bacteria that
convert sugars to lactic acid, usually:
– Lactococcus lactis subsp. lactis,
– Lactococcus lactis subsp. cremoris or
– Lactococccus lactis subsp. lactis biovar diacetylactis.
• Where flavour and aroma compounds such as
diacetyl are desired the lactic acid starter will
include heterofermentative organisms such as:
– Leuconostoc citrovorum or
– Leuconostoc dextranicum.

6. • The primary function of lactic starters is the production of lactic
acid from sugars
• Other functions of starter cultures may include the following:
• flavour, aroma, and alcohol production
• proteolytic and lipolytic activities
• inhibition of undesirable organisms

7. Benefits of fermentation
Benefit
Raw
material
Fermented
food
Preservation Milk
Yoghurt, cheese
(Most materials)
Enhancement of safety
Acid production
Acid and alcohol production
Production of bacteriocins
Removal of toxic components
Fruit
Barley
Grapes
Meat
Cassava
Soybean
Vinegar
Beer
Wine
Salami
Gari, polviho azedo
Soy sauce
Enhancement of nutritional value
Improved digestibility
Retention of micronutrients
Increased fibre content
Synthesis of probiotic compounds
Wheat
Leafy veges.
Coconut
Milk
Bread
Kimchi, sauerkraut
Nata de coco
Bifidus milk, Yakult,
Acidophilus yoghurt
Improvement of flavour Coffee beans
Grapes
Coffee
Wine

8. Thank you