Eduqas GCSE Food Preparation and Nutrition: Student Book

244 COMMODITIES Types of milk Milk is bottled according to its fat (cream) content. Most milk has a fat content of about 4%. However, during processing the fat may be reduced or removed. Channel Island milk comes from the Jersey or Guernsey breed of cows. Their milk has a higher fat content compared to other cattle breeds. Secondary processing of milk By law all milk must be heat treated to destroy any pathogenic bacteria and ensure that it is safe to drink. This heat treatment takes place at the milk processing plant and is called ‘ pasteurisation ’. Pasteurised milk ‘Raw’ (untreated) milk must be pasteurised. Pasteurisation is the process of heating the milk to 75  o C for 25 seconds and rapidly cooling it to 5  o C. This level of heating is enough to destroy most pathogenic bacteria , making the milk safe to drink without affecting its overall flavour and giving it a longer shelf life. The pasteurised milk is then sealed into containers ready for sale. Pasteurised milk, if left to settle, will form a cream layer at the surface. To prevent this from happening milk can be homogenised . Homogenised milk Homogenisation is a process that forces pasteurised milk under pressure through a very fine mesh. This action breaks up the large fat (cream) globules into smaller particles so that the cream is evenly distributed throughout the milk. This gives a uniform consistency and creaminess. Key point Cream is the fat element of milk. MilkType Fat%per 100g Channel Island Milk 5.10% Whole Milk 3.9% Semi-skimmed Milk 1.7% 1%Milk 1% Skimmed Milk 0% - 0.5% Filtered milk 0% - 3.9% The fat content of different types of milk Unhomogenised milk Homogenised milk Sterilised milk Sterilised milk is treated with much higher temperatures to destroy nearly all the bacteria in it. The milk is heated to around 50  o C, homogenised, then poured into glass bottles which are closed with an airtight seal. The filled bottles are carried on a conveyor belt through a steam chamber where they are heated to a temperature of between 110-130 ºC for approximately 10-30 minutes. The bottles are then cooled and are then ready for sale. Unopened bottles or cartons of sterilised milk will keep for approximately six months without the need for refrigeration. Once opened, sterilised milk must be treated as fresh milk and used within five days.  The sterilisation process causes a change to both taste and colour and also slightly reduces the nutritional value of the milk. The heat destroys some of the water soluble B and C vitamins. What is pasteurisation? Check it Seat Impact ring Homogenised product Valve Feed MOST MILK SOLD IN THE UK IS HOMOGENISED HOMOGENISATION PROCESS Large fat globules Small fat globules