Food processing

Overview

Food processing is the transformation of raw ingredients into food products through physical or chemical means. For your Edexcel GCSE, you must understand the entire journey, from a wheat field to a loaf of bread on a supermarket shelf. This topic is central to the specification, as it connects food science, nutrition, and food safety. Examiners expect candidates to differentiate clearly between primary and secondary processing, explain the scientific principles of preservation methods, and evaluate the impact of processing on the nutritional, functional, and sensory properties of food. High-level responses will consistently link processing techniques to their effects, such as the trade-off between extending shelf life and the loss of heat-sensitive vitamins. Mastering this area is key to achieving top-band marks, particularly in extended response questions that require evaluative skills (AO4).

Key Concepts in Food Processing

Primary vs. Secondary Processing

What it is: This is the most fundamental distinction you must know. Primary processing involves converting raw agricultural products into basic ingredients. Secondary processing takes these ingredients and combines them to create finished food products.

Why it matters: Marks are frequently awarded for correctly identifying and giving examples of each. A common error is misclassifying a process, for example, stating that cheese production is primary processing. It is secondary, as it uses milk (a primary-processed ingredient).

Specific Knowledge:

• Primary Examples: Milling wheat into flour, extracting oil from seeds, pasteurising milk, refining sugar from sugar cane.
• Secondary Examples: Baking bread from flour, making cheese or yoghurt from milk, producing sausages from meat, manufacturing a ready-meal.

Food Preservation

What it is: A set of processes designed to prevent food spoilage by inhibiting microbial growth or destroying harmful microorganisms. This extends shelf life and improves food safety.

Why it matters: Examiners require precise scientific explanations. You must be able to state the exact temperatures and times for heat treatments and explain the underlying principles (e.g., denaturation of enzymes, removal of moisture).

Specific Knowledge:

• Pasteurisation: Heating to 72°C for 15 seconds. Reduces pathogenic bacteria to safe levels but does not sterilise the food.
• UHT (Ultra-High Temperature): Heating to 135°C for 1-4 seconds. Sterilises the food, giving it a long shelf life, but can degrade heat-sensitive vitamins like Vitamin C.
• Dehydration: Removing moisture to prevent bacteria and moulds from multiplying.
• Freezing: At -18°C, microbial reproduction and enzyme activity are paused (not stopped).

Fortification

What it is: The addition of nutrients to a food that were either not originally present or were lost during processing. In the UK, the fortification of white wheat flour is mandatory.

Why it matters: This is a guaranteed area for marks if you can recall the specific nutrients and their purpose. It is a key example of how processing can be used to improve public health.

Specific Knowledge:

• Mandatory Nutrients: Calcium, Iron, Thiamin (Vitamin B1), Niacin (Vitamin B3).
• Mnemonic: Use CITN to remember them.
• Purpose: To replace nutrients lost during the milling process (when the bran and germ are removed) and to prevent deficiency diseases like anaemia (Iron) and rickets (Calcium).

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