Unit 2: Food Processing, Nutrition and Food Safety
What you must understand
Unit 2 moves from food as a system to food as a material. You need to know the main processing methods - thermal (pasteurisation, canning, blanching), low-temperature (chilling, freezing), dehydration, fermentation, irradiation and the use of additives - and explain how each affects nutritional value, shelf life, sensory properties and cost. Be able to distinguish primary processing (e.g. milling, juicing) from secondary processing (e.g. baking, canning a sauce). Know the macronutrients and micronutrients, their functions and food sources, and the concept of nutrient retention and loss during processing (e.g. water-soluble vitamins lost in boiling).
Food safety is central: know the causes of food spoilage (microbial, enzymatic, chemical, physical), the temperature danger zone (5–60 °C), the principles of HACCP as a preventive system, and hygiene practices such as the four C's (cleaning, cooking, chilling, cross-contamination). Be able to explain why a process is chosen for a particular food, not just what it is.
Traps in questions
- Confusing pasteurisation (reduces pathogens, needs refrigeration) with sterilisation/canning (destroys all pathogens, shelf-stable).
- Saying a process "destroys nutrients" without naming which nutrient and why (heat and water-soluble vitamins; light and riboflavin).
- Mixing up HACCP (preventive, hazard-based, whole-system) with end-product testing.
- Forgetting that fermentation is a controlled microbial process, not spoilage.
- Describing additives only as "bad"; questions reward explaining their functional role (preservative, emulsifier, colour).
Worked example
"Why is milk pasteurised rather than canned?" A strong answer: pasteurisation heats to about 72 °C for 15 seconds, killing pathogens such as Listeria and Salmonella while retaining sensory quality and most nutrients; the product must then be refrigerated and has a short shelf life. Canning would give a longer shelf life but would change flavour, colour and some vitamins. The choice reflects a trade-off between safety, sensory quality and shelf life.
Rule of thumb
For any processing question, state the process, the mechanism (heat, water removal, pH, temperature), the effect on microorganisms and nutrients, and the trade-off.