What is Milk
Milk is emulsion with fat globules suspended in the water phase of milk
Composition of milk?
High 80s % of water and rest is SNF (milk solids)
Nutritional and Environmental Factors affecting milk composition?
Nutritionally it is what is the cow eating and quality of the food.
Environmental factors include the age, sex and location of the cow
Physical properties of milk
- Ph – 6.6-6.8 and acidity 0.13%
- Opaque
- Density – 1.028 (same as water)
- Isotonic osmotic pressure – same pressure inside as out
- Freezing point – 0.512
Milk processing steps
Milk comes into the factory and is quality tested before being transferred to silos.
- Separation – separates cream (used for butter and ice cream) and skim milk
- Standardisation – check for legal requirements & protein is added
- Pasteurization
- Homogenisation
- Packaging
Explain Pasteurisation and Homogenisation
Pasteurisation - happens within 72 hours of the milk arriving, and kills the thermosensitive pathogenic microbes
Homogenisation - milk is forced through a high pressure narrow gap to mix the fat and the milk.
Explain the methods of Pasteurisation
LTLT- Low temp, longer time (63D for 30 mins)
HTST - High temp, short time (72D for 15s)
UTH - Ultra High Temp (135D for 2s)
Describe the solids composition of milk
When all the water is extracted and only the minerals are left
Separation of butterfat (streams) and its uses
After separation process, the butterfat is separated into two streams: fat depleted (used for skim milk) and fat rich (used to make cream)
Provide examples for beverage Milk Products?
Full fat 3.2-2.8%, reduced fat 2%, low fat 1.4% and skim 0.15%
List Concentrated & dried dairy products
- Evaporated skim and whole milk
- Sweetened condensed milk
- Condensed Whey
- Milk powder
- Whey powder
- Whey protein concentrate
Steps in yoghurt production
Milk goes through separation and standidation, followed by:
- addition of sugar, gelatin and solids (this is done to fortify the milk and increase SNF)
- pasteurized
- homogenised
- cooled 45D
- inoculate with starter cultures (ST and LB)
- add fruit
- package, store and dispatch
Bacteria’s used in yoghurt production?
- ST (Streptococcus Thermophilus)
- LB (Lactobacillus delBrueckii)
- ABC cultures
(L.acidophilus, Bifidobacteria, L. casei)
Steps in cheese making?
- separation of milk
- standardisation
- pasteurization
- additives (starter culture, colour, CaCl (reduces about of rennet needed for coag), Hydrogen Peroxide)
- coagulation - milk is heat treated to grow bacteria (45-60mins)
- curd treatment - cut into pieces for whey to be released
- whey extraction when curd reaches desired moisture and acidity
(some cheese varieties need curd washing eg. Gouda) - salting - reduces bacterial growth
- ripening - varies between cheeses and is controlled
What is Rennet?
Triggers coagulation and acts on the proteins in the ,milk to curdle it.
Concept of Emulsion
Dispersion of one fluid into another (oil in water)
Describe butters physical structure
- dense
- mostly fat and water
- clean taste
- sweet cream and salt cream
Butter production steps
- cream is pasteurized
- cooled
- aged - allows fat to solidify, 12-15 hrs
- churn and work - breaks down fat globules and then worked (plastisized) to finely disperse fat in water
- salted and packaged
What product is water in fat emulsion?
Butter
Steps in making ice cream
- mixing of white mix at 50D (milk, cream, powders, whey, butter)
- pasteurized HTST
- homogenised
- chilling and aging - fat cooled and crystals form a gel for stabilization (24hrs)
- soft freezing and beating - to incorporate air
- addition of fruits or nuts
- packaged and hard frozen
- distribution
Physical Structure of Ice cream
- water
- milk fat
- milk solids not fat
- sweeteners
- stabilizes
- one half is air
