How food is processed and produced, including primary and secondary processing, the production of staple foods such as flour, milk and cheese, fortification, and methods of food preservation.

What this dot point is asking

AQA wants you to explain how raw foods are turned into the products we buy through primary and secondary processing, how staple foods such as flour, milk and cheese are made, what fortification is, and how food is preserved to last longer.

Primary and secondary processing

Producing staple foods

• Flour - wheat is milled (ground) and sieved; the bran and germ may be removed to make white flour or kept for wholemeal.
• Milk - it is pasteurised (heated briefly to kill bacteria) and usually homogenised (so the cream does not separate).
• Cheese - rennet (and a starter culture) is added to milk to curdle it into curds and whey; the curds are then processed and matured.

Fortification

Food preservation

Preservation extends shelf life by removing one of the conditions bacteria need (warmth, moisture, time or a suitable environment):

• Freezing - very low temperature stops bacteria multiplying.
• Canning and bottling - heat treatment kills bacteria, then sealing keeps them out.
• Drying and dehydrating - removes the moisture bacteria need.
• Pickling, salting and sugaring - acid, salt or sugar create conditions bacteria cannot grow in.
• Chilling - slows growth but does not stop it.

Each method works by removing one of the conditions micro-organisms need. Low temperature (freezing, chilling) slows or halts multiplication; high temperature (canning, pasteurising, UHT) kills micro-organisms; removing water (drying); and creating a hostile chemical environment (acid in pickling, high salt or sugar concentrations that draw water out of microbial cells by osmosis). Modern methods such as vacuum packing and modified atmosphere packaging remove or replace oxygen so spoilage organisms cannot grow.

Processing has effects beyond shelf life. Primary processing can cause some nutrient loss (milling out the bran and germ removes fibre and some vitamins, which is partly why white flour is fortified by law). Heavily processed (ultra-processed) foods are often high in fat, sugar and salt and low in fibre, which is why nutrition advice favours less processed, whole foods where possible.

Try this

Q1. Give one example of primary processing and one of secondary processing. [2 marks]

• Cue. Primary: milling wheat into flour or pasteurising milk. Secondary: making bread or cheese sauce.

Q2. Explain how drying preserves food. [2 marks]

• Cue. It removes the moisture (water) that bacteria need to grow, so they cannot multiply.