Food processing and production Flashcards
What is primary processing?
- Prepares raw food to be eaten, cooked immediately or used as an ingredient
How is wheat processed to produce flour?
- A wheat grain is made of bran (mostly fibre), endosperm (mostly starch) and germ (vitamins, protein and fat)
- Wheat grains are harvested and then cleaned to removes any stones or dust
- Water softens the outer layer (bran) of the grain
- It’s blended with other types of wheat in a process called gristing
- The grist is passed through fluted break rolls rotating at different speeds so the wheat is sheared open
- The fragments of the wheat are separated by sieves
- The endosperm go through reduction rolls for final milling
- Coarser pieces of bran are passed through the rolls again
- In the end, wheat is separated into flour, germ and bran
What are 3 different types of flour, their components and extraction rates?
- Wholemeal flour contains all of the parts of wheat grains, and so has an extraction rate of 100%
- Brown flour does not contain the bran, so it had an extraction rate of 85-90%
- White flour has an extraction rate of 70-75% as it doesn’t contain the germ or the bran
What is milk like, and what is done to it as a result?
- Milk is an emulsion of oil in water, so the fat rises to the top and creates a cream line
- Homogenisation is the process of forcing milk at high pressure through small holes, which breaks up fat globules
- This spreads them out evenly in the milk
Why is milk heat-treated, and list 3 ways this is done.
- To destroy pathogenic bacteria
- Pasteurised: heated to at least 72°C for 15 seconds, then cooled below 6°C
- Sterilised: heated at 110°C for 10-30 minutes, then cooled
- Ultra heat treatment (UHT): heated to 135°C for 1 second and put into sterile, sealed containers
List 2 issues with heat-treated milk.
- All of the bacteria in sterilised milk is killed, so it tastes different and many group B and C vitamins are lost
- UHT milk has slightly less nutritional value and a different taste to pasteurised milk
How are fruits and vegetables processed to become a food product?
- Fruits and vegetables are washed with water to remove dirt, insects and chemical sprays
- They’re sorted into different sizes and shapes
- Pits are removed
- They’re squeezed for juice/ dried/ crushed or pressed to extract oils
How is meat processed?
- Some (like beef) are hung and dried to make them more tender and improve their flavour
- The feathers and internal organs of poultry are removed
- The wings and legs of poultry are tied so it cooks evenly
- Meat is chopped, sliced or cut
How is cream made?
- The fat in milk rises to the top as it is less dense, and can be ‘skimmed off’ (to aid the separation, milk is rotated at a fast speed)
- The cream is then pasteurised to kill pathogenic bacteria and enzymes that affect its taste and would shorten its shelf life
- Different types of cream have different amounts of milk fat (single cream has 18%, and double cream has 48%)
How is butter made?
- Cream is churned to remove more liquid
- This agitates the cream until the fat droplets stick together
- The cream gets thicker until it forms a solid mass of butter
- Butter has a fat content of between 80 and 90%
How is cheese made?
- The milk is pasteurised to kill pathogenic bacteria
- Bacteria is added to turn lactose into lactic acid to help coagulate the protein in milk, preserve the cheese and to develop a sour flavour
- Rennet is added and the mixture sets into solid cheese curds
- The whey (remaining liquid) is removed
- In soft cheese it is allowed to drain away naturally, but in hard cheeses the curds are heated and piled on top of each other to remove more whey
- The cheese is milled, salt added for certain types, and pressed into moulds
- It is left to mature
- Bacteria or mould may be added to change the flavour
How is yoghurt made?
- The milk is pasteurised and homogenised
- Bacteria are added that that change lactose to lactic acid, which causes it to coagulate (thicken) and gives it a sour taste
- The yoghurt is left until it reaches the correct level of acidity
- Fruit and flavourings are added
How is pasta made from flour?
- It is mixed with eggs or water
- The dough is shaped by forcing it thorugh a metal die, and it is then folded or twisted
- Colourings may be added
- Pasta is then sold either fresh or dried
How is bread made from flour?
- Flour is mixed with water and yeast to make a dough
- The dough is kneaded to develop the gluten
- The dough is proved to let the yeast ferment
- The dough is baked in the oven
How are foods canned?
It’s a from of sterilisation.
- Food is either packed into a can and then sterilised
- Or it can be sterilised and placed in aseptic cans
- They’re then sealed to prevent leakage and contamination
What are 2 disadvantages of caning foods?
- Their texture might change
- Canned foods lose B group vitamins and vitamin C
List 5 low temperature methods of preserving food. Why do they work?
They slow down the speed that bacteria reproduce at, and freezing food makes bacteria dormant.
- Chilling
- Freezing
- Cook-freeze
- Blast chilling
- Accelerated freeze- drying (AFD)
How are foods chilled?
- They’re cooled to between 0 and 5°C
How are foods frozen?
- They’re cooled to -18°C
What does it mean to cook-freeze a food?
- The food is cooked, then rapidly frozen
What is blast chilling?
- Blast-chillers rapidly cool cooked food to below 5°C within 90 minutes
What is accelerated freeze-drying (AFD)?
- Food is rapidly frozen and dehydrated to remove moisture
- Adding water to the food restores the food to its original texture and taste
Describe drying foods.
It works as microorganisms need moisture, so without it they cannot grow.
- Hot or warm temperatures are used to remove the moisture
- Dried foods need to be stored in a cool, dry place
- Their colour, taste, texture and nutritional value can be affected
What impact does smoking foods have?
- The food is dipped in salt or an acid solution first
- Chemicals in the wood being burnt give it flavour and help preserve it
How do acids, salt and sugar preserve food?
- They either kill bacteria or stop them from reproducing
- Bacteria cannot survive beneath a pH of 4.5 (vinegar’s pH is 3.5)
- Salt reduces moisture by osmosis
- In high enough concentrations (over 60% of the product) sugar makes water unavailable, so bacteria cannot grow
What is monitored/ controlled atmosphere packaging (MAP/ CAP)?
- It slows down the growth of microorganisms as they use oxygen for growth, which increases the shelf life
- Fresh foods are packaged
- The air around it is replaced through ‘gas flushing’ (different proportions of oxygen, nitrogen and carbon dioxide according to the food)
- Sealed with a plastic bag or lid to make the container airtight
- As a result once the container is opened, the food has a regular shelf life
- It is used for chilled meat, fruits and vegetables
What is vacuum packing?
- Air is removed from the package and it is sealed
- The food is kept in anaerobic conditions, which prevents bacteria from growing
- Once opened it has a regular shelf life
- The food maintains its colour and texture
