Dairy Products

• To destroy/remove any harmful bacteria which will cause rapid spoilage of the milk

• Pasteurisation- short term method (HTST)
  • heating milk lower then boiling point but at a temperature high enough to kill harmful bacteria/organisms and reduce spoilage organisms (99% killed)
  • 72C for 15 seconds
  • 'use by' and stored in a fridge
  • Half vitamin C lost
• Sterilisation
  • canning at 120C for minutes or hours
  • destroys all microorganisms and spores
  • strong cooked milk flavour
  • colour and flavour change- orangey/ yellow

• It is carried out to prevent separation of the cream layer
• it is essential when milk is subjected to high temperatures
• warmed to 60C and forced through a small gap in a pressure homogenises (reduces fat droplets)
• small fat droplets are very stable and doesn't separate out into a cream layer

• Vitamin C content is halved
• 10% thiamine and B12 lost
• Protein around the fat globules slightly denature causing fat gloubles to stick together and rise to the surface forming a cream layer

• Varies according to the breed (most important), age, stage of lactation, season, feed
• Contains Carbohydrates, Lipids and Proteins
• Milk is an emulsion -> fat in water 

• It is saturated fatty acid -> triglyceride
• held in a suspension (as globules) - fat in water emulsion
• fresh milk will produce a 'cream layer' on standing where fat globules rise to the surface (homogenisation prevents this)
• milk is a stable emulsion
• milk contains a natural emulsifier which is in the protein of milk

• The protein in milk is catergorised into two groups
  • Casein (a curd precipitated by acid or enzyme rennin)
  • Whey (liquid - lactoglubulin and lactalbumin)
• Casein is a mixture of phosphoproteins -80% of milk - rest from whey
• Casein is in to parts - a-casein (can be coagulated by calcium), k-casein (insensitive to calcium) 
• the k-casein surrounds the a-casein
• k-casein is destroyed by the action of rennin, which then allows calcium to react with a-casein
  • this caused the formation of curd
  • proteins left after this are known as whey

• Consists of the disaccharide lactose
  • formed for glucose and galactose
    • also called milk sugar
• Absorption of lactose depends on presence of an enzyme lactase
• the amount of lactase defines the amount of lactose absorbed
  • lactose intolerance
• curdling and clotting are not the same chemically

• milk can sour easily, even when under a chilled condition
  • contains bacteria known as lactic bacilli
    • which brings the breakdown of lactose into lactic acid
• soured milk pH drops to 5.2 and so the milk curdles 
  • casein is broken down to form curds

• this happends naturally from lactic acid produces
• has the same affect when any acid added

• (Rennin is added and the milk is warmed)
• The enzyme rennin is resposibile for milk clotting
• It breaks down the k-casein
• which allows the calcium to react with a-casein
• this then forms a curd
• leaving the liquid whey
• this happens naturally in the stomach and in cheese making

Full fat = 3.9%

Semi Skimmed = 1.6%

Skimmed = 0.1%

• Vitamins
  • It contains all the minerals needed for a baby
  • particularly rich in calcium and phosphourus
  • iodine
  • chlorine
  • iron
  • sodium
• Minerals
  • Vitamin A and D - found in milk fat (very low in skimmed)
  • Vitamin B - riboflavin/ thiamin
  • Vitamin C
  • both thiamin and vitamin C are destroyed by heat treatment