Preparation for PFA

Dairy Technology
Definition:
Milk is a lacteal secretion of mammary glands

Milk Composition:
1. Water 85-90%
2. Fat ( Triglycerides ) 4.0%
3. Fat ( Mixed Milk) 4.25%
4. Protein ( Casein and Whey ) 3.3%
5. Lactose ( Disaccharide, Reducing sugar ) 4.6%
6. Vitamins Trace amount
 Lacks Vitamin C
7. Minerals 0.7%
 Lacks iron

Structural elements:
1. Fat Globule:
 Macro molecules
 Complicated structure
 Crystallized at temperature below 35C
 When fat globules are removed, the remaining milk is called milk plasma
2. Casein Micelles:
 Consist of water, protein and salts
 Milk in which fat globules and casein micelles are removed is called milk serum
3. Serum Protein:
 Small aggregates
4. Lipoprotein particles:
 Microsomes
5. Cells:
 Leukocytes
 0.01%
 Rich in enzyme i.e. Catalase

Milk Excretion:
 Alveoli
 Lumen
 Cistern
  Teats

Properties of Milk:
1. Boiling point 100-101C
2. Water activity 0.995
3. Freezing point -0.54C
4. Specific gravity 0.93

Changes in Milk:
1. Physical
 Air incorporated
 Fat globule may damage
2. Chemical
 Due to oxygen, some substances may oxidized
 Light may induce reactions, leading to off flavors
3. Biochemical:
 Due to enzymes
 Lipase
 Proteinase
 Phosphatse
4. Microbial:
 Lactic acid production
 Reduction of pH
Lifeline: Cooling of milk at 4C after milking can prevent these changes

Heat Treatments:
1. Low Pasteurization
 74C for 15 seconds
2. High Pasteurization
 90C for 15 seconds
3. Sterilization
 118C for 20 minutes
4. UHT
 145C for few seconds
Microbiology of Milk
 Diameter of Bacteria is less than 1um
 Many bacteria are rod shaped, spherical, spiral
 Reproduction occurs by binary division/ fission
 Bacillus and Clostridium form endospores
 Some lactic acid bacteria produce exopolysaccharides during growth in milk, it may
affect the structure of fermented product
 Locomotion due to flagella
 Geotrichum candidum is a milk fungus
 Molds in the genera Aspergillus and Penicillium form conidiospores
 Test for bacterial count are Standard plate count and Bactoscan
 Psycrophiles 0-20c
 Mesophiles 20-45C
 Thermophiles 45-60C
 Bacterial inhibitors are Lysozyme and Lactoferrin
 Pencillin is given to treat Mastitis
 Bacteria cannot survive <4.5 pH

 Mostly filtration membranes are made up of Polyether sulfone

 Fermentation
1. Lactic acid Bacteria:
 Total 12 genera, 4 genera are responsible for dairy fermentation ( Lactococcus,
Leuconostoc, Streptococcus, Lactobacillus )
 Gram positive
 Non spore formers
 Non motile
 Anaerobes
 Require B vitamins for growth

Genera Temp. Range Ferm. Mode

Lactococcus Mesophilic Homo-fermentative

Leuconostoc Mesophilic Hetero-fermentative

Streptococcus Thermophilic Homo-fermentative

Lactobacillus Thermophilic Homo-fermentative

2. Biochemistry:
 Bacteria convert lactose to lactic acid
 They convert citric acid to Diacetyl ( Flavoring compound )
 Bacteria use casein as a source of Nitrogen
3. Bacteriosins:
 Bacteria produce proteins that inhibit the growth of other bacteria
 Nisin is a bacteriosin and produced by Lactococcus lactis
 Nisin is also called lantobiotic because of the amino acid lanthionine
 Nisin inhibits Bacillus, Clostridium, Staphylococcus and Listeria
 Clos. Tyrobutyricum causes late gas production in semi hard cheese

Cleaning
1. CIP steps:
 Water
 Alkali
 Water
 Acid ( Nitric or Phosphoric acid)
 Water
Milk Products
1. Pasteurized milk:
 Raw milk 4% fat
 Filter
 Cooling 4C
 Centrifuge 60C (Cream, 40% fat)
 Skim Milk (Cream, 12% fat, Homogenize 10 MPa)
 Standardized milk
 Pasteurize (75C for 20 seconds)
 Cooling 4C
 Packaging
 Storage (Dark 4C)
Note: Plasmin is not inactivated by Pasteurization
2. Whipping cream:
 Milk
 Pasteurize (72C 15 seconds)
 Centrifuge (50C)
 Cream
 Standardize (36% fat)
 Pasteurize (85C for 30 mins.)
 Cool (5C)
 Pack
 Cold storage (24 hrs. 4C)
3. Ice Cream:
 Milk
 Centrifuge (40-50C)
 Cream
 Standardize (Additives and sugar added)
 Mix
 Pasteurize (80c for 25 seconds)
 Homogenize (15 MPa)
 Cool (4C)
 Ripening (4-24 hrs.)
 Freezing (-5C)
 Ice cream
Say Cheese!
1. Definition:
Cheese is the fresh or matured solid or semisolid product obtained by coagulating milk,
skimmed milk, partly skimmed milk, cream, whey cream, or buttermilk, or any
combination of these materials, through the action of rennet or other suitable coagulating
agents, and by partially draining the whey resulting from such coagulation.

 Fresh cheese has a shelf life of 2 weeks under refrigeration

 If raw milk is used for cheese, Coliforms and propionic acid bacteria will grow and
off flavors are produced by Lactic acid bacteria
2. Milk Treatment for cheese preparation:
 Thermalization, if milk is to be kept for sometime
 Pasteurization (inactivate alkaline phosphatase)
 Bactofugation (To reduces the spores of Clos. tyrobutyricum)
 Addition of Calcium chloride (To speed up clotting)
 Addition of potassium or sodium nitrate (Control coliform and butyric acid
bacteria)
3. Enzymes used:
 Chymosin (Endopeptidase)
 Rennet
 Porcine pepsin
Note: Heating milk more intensely than low pasteurization causes an increased clotting
time, a weaker curd, and impaired syneresis
4. Process flow (Cheddar cheese):
 Milk
 Pasteurize (71C for 15 seconds)
 Pre-acidify (Starter 2%) (30C for 40 mins.)
 Renneting (35 mins.)
 Cutting (10 mins.)
 Scalding
 Stirring
 Sedimenting
 Cheddaring
 Milling
 Mixing
 Resting
 Filling
 Pressing
 Drying (4days 12C)
 Packing
 Curing (8C)
Definitions
Milk:
Milk is a lacteal secretion of mammary glands
Milk plasma:
Milk minus fat globule
Milk serum:
Milk minus fat globules and casein micelles
Homogenization:
Reduction in fat globule size
Skim milk:
Milk having very low fat content or Milk from which fat is removed
Mastitis:
When pathogenic bacteria enter a mammary gland, a severe inflammation can result, called
mastitis.
Test for mastitis:
The somatic cell count (number of cells per milliliter) is taken as a
measure of the severity of the mastitis and of the change in milk composition.
Food infection:
Food acts as a carrier for microbes, which enter the human body through the food
Food poisoning:
Microbes form toxin in the food and the ingestion of toxin results in food poisoning.
Centrifugation:
Separation of solid particles (fat) from milk
Bacteriophage:
A virus that can infect and kill bacterial cells
Reconstituted milk:
It is made by dissolving whole milk powder in water to obtain a liquid that is similar in
composition to whole milk.
Recombined milk:
It is made by dissolving skim milk powder in water, generally at 40 to 50°C, then adding liquid
milk fat (preferably anhydrous milk fat of good quality), making a coarse emulsion by vigorous
stirring or with a static mixer, and then homogenizing the liquid.
Whipping Cream:
This involves cream of, say, 35% fat. It is mostly available as a pasteurized product in small bottles,
plastic cups, or large cans. It is also sold as in-can sterilized cream.
Evaporated milk:
Milk with reduced water content, having fat content 7.8% and concentration factor is 2.1
Sweetened Condensed Milk:
Milk with reduced water content (27%), fat content (8%) and lactose content (10.3%).
Deterioration usually occurs by osmophilic yeasts, most of which belong to the genus Torulopsis
Probiotics:
Live microbial cultures that influence the health of the host by improving its indeginous
microflora.
Prebiotics:
Non-digestible food ingredient that stimulate the growth of one or limited number of bacteria in
cosslon.
Mozzarella cheese:
The cheese contains 35 to 45% fat in the dry matter, 52 to 56% water, and about 1% salt.