Food Processing And Production Flashcards
Examples of primary processing
- milling wheat into flour
- heat treating milk
Etc
Processing of wheat
- Stones and other grains like barley are removed
- Water softens the bran layer
- The wheat is blended with other types of wheat (gristing)
- Stage 1: grist passes through the ‘break rolls’ (separate the inner portion from the outer skins)
- Stage 2: the wheat grains are separated by sieving
- Coarser bran pieces with endosperm repeat stage 1 and 2 until all flour, bran and wheat germ are separated
Types of flour
Strong flour: has a higher gluten content
Soft flour: used for cake and pastry making and has a lower gluten content
Self-raising flour: this has a chemical raising agent added to it
Gluten-free flour: has had the protein removed from it (for those with coeliac disease)
Processing of milk
- milk is mainly water and an emulsion with tiny fat droplets -> as oil and water don’t mix, the fat rises to the top
- most of the milk is homogenised -> involves forcing the milk at high pressure through small holes
Effects of pasteurising milk
- kills harmful bacteria
- little effect on nutritional value
- extends the milks shelf life
Effects of sterilising milk
- destroys nearly all the bacteria
- changes the taste and colour
- destroys some vitamins
Effects of UHT milk
- have long shelf life when unopened
- little effect on flavour or nutritional value
Examples of secondary processing
- making wheat into pasta, bread etc
- making milk into cheese, butter and yoghurt
Main ingredients of bread
- flour -> strong plain flour, as the gluten content is higher
- yeast -> to make the bread rise
- salt -> to add taste and help proving
- vegetable fat -> to make loaf lighter and extend its shelf life
- water
How bread is made
- Flour and other ingredients are delivered to bakery
- Ingredients are mixed at high speed, the dough mixture is removed then passed along a conveyor belt and is left to prove
- The dough is continuously kneeded for about 2 minutes then passed along a belt and swapped into pre-greased baking tins
- The second proving stage takes place
- The loaves pass in a belt slowly through an oven for 20 minutes at 230*C
- The baked loaves come out of the oven in the cooling area and left to cool then sliced and bagged
How flour is made into pasta
- Flour is mixed with liquid
- A lumpy dough is formed
- The dough is put into an extruded where the gluten is developed and forced through different shaped dies or rolled
- The pasta is then dried
- It is packed to be sold
How butter is made
Made by churning cream to remove even more liquid
How is cream made from milk
- cream is the fat found in milk
- the cream is separated by rotating it at a fast speed
- the cream is then pasteurised to kill any harmful bacteria (this also destroys enzymes which can affect the flavour and shorten shelf life
How is yoghurt made from milk
- milk is pasteurised
- the milk is homogenised
- milk is incubated and the harmless bacteria are added
- the yoghurt is left to set until it reaches the correct acidity level
- fruit or flavourings are then added
How is cheese made from milk
- milk is pasteurised and cooled to 30*C
- started culture of bacteria is added
- rennet is added and the mixture is left to set
- the curd is cut so the whey is released
- for soft cheese the whey is left to drain away naturally but for hard cheese the curds are heated and liked on top of each other to release more whey
- the cheese is then milled and for many salt is added
- curd is pressed into moulds
- the cheese is left to ripen
Advantages of preserving food
- prevents the action of enzymes
- lasts longer
- can buy products when they’re not in season
- prevents microorganism from multiplying
- increases the range of foods available
- increases shelf life of food
Disadvantages of preserved food
- often contains a lot of fat, sugar and salt
- doesn’t contain a lot of fibre
- texture may change
- can be more expansive than fresh foods
- additives may be added to restore colour lost in processing
- some nutrients are lost when it is processed
Pasteurisation
- food is heated to 75*C for 15 seconds
- destroys pathogenic microorganisms
- shelf life is extended
Sterilisation
- food is heated for a long period of time at higher temps
- destroys nearly all microorganisms and enzymes
UHT (ultra heat treatment)
- uses very high temperatures for up to 5 seconds
- destroys all bacteria
- extends shelf life
- little loss of nutrient content
Canning
- form of sterilisation
- texture may change
- there is some loss of B vitamins and C
Low temp methods
Slow down the speed at which bacteria reproduce but don’t destroy bacteria
Blast chilling
Foods cooked as quickly as possible
Cook-chill foods
- This is a short term way of preserving fresh food
- short shelf life
Advantages of cook chill foods
- very little change to nutritional value
- easy to prepare
- saves energy in the home
- fewer additives needed during manufacture
- consistent quality
- little waste
Freezing
- food is stored in a freezer between -18C to -29C
- no water is available for the microorganisms to grow
- little change to nutritional value
- longer shelf life
Dehydration (in preserving food)
- water is removed so microorganism can’t grow
- have longer shelf life
- flavour, colour, texture and nutritional value are affected
Other methods of preserving
Chemicals: destroys harmful bacteria or stops them reproducing
Vinegar: low pH which bacteria can’t survive in
Salt: used to coat foods like ham, bacon to reduce moisture content
Sugar: prevents bacteria from growing
Smoking: give food flavour and help preserve it
MAP (modified atmosphere packaging)
- food is packaged in peak condition
- air is replaced by ‘gas-flushing’ a combination of gases around the food
Vacuum packaging
- done by removing air and sealing the package
- the food is kept in anaerobic conditions
- food maintains colour and texture
