Food Production, Processing and Preservation Technologies
Why food is processed
Understand processing aims: extending shelf life, improving safety, improving palatability, adding convenience, enabling transport and reducing waste. Preservation works by removing or inhibiting the agents of spoilage: microorganisms, enzymes, oxygen, moisture and pests. Know the hurdle concept, where several mild preservation methods combine to control spoilage more effectively than one severe method.
Preservation methods and their principles
Know that heat treatments differ in intensity: pasteurisation (about 72°C for 15 seconds) kills pathogens and reduces spoilage organisms but requires refrigeration, while sterilisation and canning destroy all viable organisms and allow ambient storage. Understand refrigeration and freezing (lower temperature slows microbial growth and enzyme activity), drying and dehydration (removing water lowers water activity), salting and sugaring (reducing available water), acidification (lowering pH), fermentation (beneficial microorganisms produce acid or alcohol), vacuum packaging (removing oxygen), modified atmosphere packaging, irradiation and the use of chemical preservatives.
Processing effects on nutrients
Know that heat destroys heat-labile vitamins, that water-soluble vitamins leach into processing water, and that milling removes fibre and micronutrients from grains. Traps include confusing pasteurisation with sterilisation, and assuming freezing kills microorganisms (it does not; it only stops or slows growth).
Rule of thumb
For every preservation method, state the spoilage agent it targets and the principle by which it acts.
Worked example
A question asks why dried fruit keeps longer than fresh fruit. Drying removes water and lowers water activity, so microorganisms cannot obtain the moisture they need to grow; enzymatic browning is also reduced. The principle is moisture removal, and the hurdle concept explains why sulfite dipping or acid treatment may be added alongside drying.