This document discusses the scope and application of microbiology in the dairy field. It describes how microorganisms like bacteria, yeasts and molds are used in fermenting milk to produce foods like yogurt and cheese. Specific bacteria, including strains of Streptococcus, Lactococcus, Lactobacilli and others are commonly used as starter cultures to control fermentation and impart desired flavors. Enzymes are also discussed and used for processes like coagulating casein in milk for cheese production. Overall the document provides an overview of microbiology's role in the dairy industry through controlled use of microbes and enzymes.

1. Scope and
Application of
microbiology in field
of Dairy

2. Introduction:
 Dairy microbiology can be defined as the branch of
microbiology, which deals with the activities of the
microorganism in the milk and milk products.
 It includes the study of the morphology, classification and
the chemical activities of the microorganism in the milk
and milk products.
 Dairy starter cultures are carefully selected
microorganisms, which are deliberately added to milk to
initiate and carry out desired fermentation under
controlled conditions in the production of fermented milk
products.

3. Introduction:
 These are the bacteria, yeasts, molds are seldom
encountered in fermented milk production.
These microbes are of two types
i.e. favorable : which bring favorable changes in flavor &
appearance
Unfavorable: while other pathogenic – which may cause
diseases.
 The favorable are carefully propagated while pathogenic
(unfavorable) are destroyed to make the milk & its
products safe for human consumption.

4. Beneficial Microorganisms Used in Dairy
Products:
Bacteria : Bacteria are the most common and probably the
most numerous of the microorganism with which the dairy–
processing industry is concerned.
 Bacteria are microscopic unicellular which occur in the form
of spherical, cylindrical, or spiral cells, and which reproduce
by transverse fission.
 Some bacteria cause trouble in the dairy industry because
of their resistance to pasteurization and sanitation process.
Some commonly found bacteria are: Streptococcus,
Micrococcus, Lactococcus, Pediococcus, Sarcina, Bacillus,
Bacterium, Pseudomonas, Lactobacillus, Escherichia,
Aerobacter and Spirillum etc.

5. Types of bacteria found in milk and milk
products:
The acid producing: Those bacteria, which are responsible
for conversion of lactose to lactic acid, are included in this
group.
Streptococcus lactis, Streptococcus cremoris, Lactobacillus
acidophilus, Lactobacillus bulgaricus
Aroma producing bacteria: These bacteria are responsible
for the production of desirable aroma and flavor in milk
product. By utilizing citric acid and lactic acid they produce
volatile acid such as acetic acid as well as diacetyl and
other compound, which gives flavor and aroma.
Eg. Streptococcus citrovorus, Streptococcus paracitrovorus,
Streptococcus diacetilactic.

6. Types of bacteria found in milk and milk
products:
Gas producing bacteria: These are undesirable type of
bacteria that ferment lactose and produce acid and gas i.e.
lactic acid and co2.
E. Coli, Aerobacter acrogens
Peptonizing type of bacteria: These bacteria show
tendency to break down the casein by a proteolysis or
peptonization, which gives off flavor and unpleasant odors
in milk.
Eg. Bacillus subtilis, Bacillus mesentericus, Bacillus
mycoides, Bacillus noves
Ropiness type of bacteria: These organism form gum like
substances.
Eg. Alligenes viscosus, Alcaligenes viscolactis

7. Types of bacteria found in milk and milk
products:
Toxin producing bacteria: Salmonella,
Staphylococcus produce poisonous substances which are
toxic to man and animals.
Yeast
Yeast are also microscopic, unicellular, non-chlorophyll bearing
plants but are larger in size than bacteria. The yeast most
frequently encountered in milk and milk products act upon
the lactose to produce acid and carbon dioxide.
Yeast of significant importance imparts flavour and aroma in
dairy products. Genera of yeast like Saccharomyces, Torula
,Mycoderma, Candida etc.

8. Types of bacteria found in milk and milk
products:
Mold: Molds are multi cellular organism, which are not visible
to our naked eye, at maturity they may observe as
mycelium. Generally aerobic moulds are significant to dairy
products.
It is used in mould ripened cheese varieties. Moulds are
black, blue, green, gray or white.
It causes discoloring of milk along with producing smell and
odors. Common genera are Penicellium, oospora,
Aspergillus , mucor, Monilia etc.
 Some genera of moulds are of significant importance in
different types of cheese production while others work for
spoilage of dairy products under their favourable
conditions.

9. Types of bacteria found in milk and milk
products:
Viruses:
In dairy industry, only those viruses that are parasitic on LAB
and known as starter Bacteriophage is of importance.
The lactic phages are usually not destroyed by normal
pasteurization of milk employed for cheese and cultured
buttermilk, but they can be destroyed by higher heat
treatment.

10. The major roles of starter culture during
fermentation of milk are:
a) Production of primarily lactic acid and few other organic
acids, such as formic acid and acetic acid.
b) Coagulation of milk and changes in body and texture in
final products.
c) Production of flavouring compounds, e.g., diacetyl,
acetoin and acetaldehyde.
d) Help in ripening of cheeses by their enzymatic activities.
e) Produce antibacterial substances in the finished product.
f) In addition, they may possess functional properties.

11. An ideal starter culture should be
selected for the preparation of various
fermented milks with the following
characteristics:
 It should be quick and steady in acid production.
 It should produce product with fine and clean lactic
flavour.
 It should not produce any pigments, gas, off-flavour and
bitterness in the finished products.
 Should be associative in nature in product development.

12. Enzymes Used in the Dairy
Industry:
In the field of biotechnology, there are many industrial
applications that result in biotech products that we use
every day at home.
Some of these are food science applications that utilize
enzymes to produce or make improvements in the
quality of different dairy products.
In the dairy industry, some enzymes are required for the
production of cheeses, yogurt and other fermented dairy
products while others are used in a more specialized
fashion to improve texture or flavour.

13. Enzymes Used in the Dairy
Industry:
Proteases:
 Milk contains a number of different types of proteins, in
addition to the caseins.
 Cow milk also contains whey proteins such as
lactalbumin and lactoglobulin.
 The denaturing of these whey proteins, using proteases,
results in a creamier yogurt product.
 Destruction of whey proteins is also essential for cheese
production.

14. Enzymes Used in the Dairy
Industry:
Rennet:
Milk contains proteins, specifically caseins that maintain its
liquid form.
Proteases are enzymes that are added to milk during
cheese production to hydrolyze caseins, specifically
kappa casein which stabilizes micelle formation
preventing coagulation.
Rennin and pepsin are general terms for any enzyme used
to coagulate milk.
Technically rennet is also the term for the calf's fourth
stomach.

15. Enzymes Used in the Dairy Industry:
Lactase: Lactase is a glycoside hydrolase enzyme that cuts
lactose into its constituent sugars, galactose and glucose.
Without sufficient production of lactase enzyme in the small
intestine, humans become lactose intolerant, resulting in
discomfort (cramps, gas and diarrhea) in the digestive tract
upon ingestion of milk products.
Lactase is used commercially to prepare lactose-free
products.
It is also used in the preparation of ice cream, to make a
creamier and sweeter tasting product. Lactase is usually
prepared from Kluyveromyces spp. of yeast
and Aspergillus spp. of fungi.

16. Enzymes Used in the Dairy Industry:
Catalase:
The enzyme Catalase has found limited use in one
particular area of cheese production.
Hydrogen peroxide is a potent oxidizer and toxic to cells.
It is used instead of pasteurization, when making certain
cheeses such as Swiss.
In order to preserve natural milk enzymes that are
beneficial to the end product and flavor development of
the cheese.

17. Enzymes Used in the Dairy Industry:
Lipases: Lipases are used to break down milk fats and give
characteristic flavours to cheeses.
Stronger flavored cheeses,
Example: the Italian cheese, Romano are prepared using
lipases.
The flavor comes from the free fatty acids produced when
milk fats are hydrolyzed.
Animal lipases are obtained from kid, calf and lamb while
microbial lipase is derived by fermentation with the fungal
species Mucor meihei.

18. Some of the most popular and common cultured dairy
products are yogurt and cheese:
Records of yogurt preparation as food date back to
centuries BC.
Classic yogurt is the result of the fermentation of two main
bacterial species: Lactobacillus
bulgaricus and Streptococcus thermophilus.
Sometimes other lactic acid bacteria are added as well.
Yogurt is most often made of cow’s milk although milk from
sheep, goat, buffalo, camels and yaks is used as well
depending on the region of cultivation.

19. Yogurt has been traditionally consumed in cultures as a
cold drink after mixing with water (e.g., lassi, ayran,
doogh).
After the industrialization of yogurt production in the
twentieth century, yogurt with added sweetener and fruit
or fruit jam has become popular in the Western world.

20. The research has been focused on curing or preventing a
number of diseases like diarrhea, intestinal
inflammations, urogenital infections, allergies, etc.
Some species have been prepared and sold as nutritious
supplements.
However, so far there has not been enough evidence to
establish a definite cause and effect relationship about
any of the marketed products.

21. Food fermentation has been said to serve five main
purposes:
 Enrichment of the diet through development of a
diversity of flavors, aromas and textures in food
substrates.
 Preservation of important amounts of food through lactic
acid, alcohol, acetic acid and alkaline fermentations.
 Biological improvement of food substrates with protein,
essential amino acids, essential fatty acids, and
vitamins.
 Removal of anti-nutrients.
 A decrease in cooking time and fuel requirement.

24. LAB's commonly found in dairy products include strains
Streptococcus,
Lactococcus,
Lactobacilli,
Bifidobacteria,
Enterococcus, and
Pediococci.
Within these species there are numerous strain types
which can be used in fermentation processes to give
specific acidification and flavour profiles to the final
product.

25. Microorganisms and its uses:
 Production of dairy products and other industries:
Bacteria are the key players here. ...
 Bread Baking: ...
 Alcoholic Drinks: ...
 Organic acids: ...
 Enzymes: ...
 Steroid production: ...
 Help in sewage treatment: ...
 Used as insecticides:

26. The End…