Principles of nutrition — WJEC GCSE Food Preparation and Nutrition Revision
The science of food covers the theoretical and practical understanding of how preparation and cooking affect the sensory and nutritional properties of food
Topic Synopsis
The science of food covers the theoretical and practical understanding of how preparation and cooking affect the sensory and nutritional properties of food. It includes heat transfer methods, the role of microorganisms, functional and chemical properties of ingredients (carbohydrates, fats, proteins, fruit/vegetables), food spoilage, and food safety principles.
Key Concepts & Core Principles
- Macronutrients: Carbohydrates (simple and complex), proteins (high and low biological value), and fats (saturated, unsaturated, and trans) – their sources, functions, and energy yields (17 kJ/g for carbs and protein, 37 kJ/g for fat).
- Micronutrients: Vitamins (fat-soluble A, D, E, K and water-soluble B group, C) and minerals (calcium, iron, sodium, etc.) – their roles in the body and deficiency diseases (e.g., scurvy from vitamin C deficiency, anaemia from iron deficiency).
- Dietary Reference Values (DRVs): Understanding Estimated Average Requirements (EAR), Reference Nutrient Intake (RNI), and Lower Reference Nutrient Intake (LRNI) for different age groups and genders.
- Energy balance: The relationship between energy intake (from food) and energy expenditure (basal metabolic rate + physical activity), and consequences of imbalance (weight gain/loss).
- Dietary guidelines: The Eatwell Guide proportions (fruit and veg, starchy carbs, proteins, dairy, oils) and current UK health recommendations (e.g., <70g fat/day, <20g saturated fat, <6g salt).
Exam Tips & Revision Strategies
- Use specific scientific terminology (e.g., gelatinisation, denaturation) in all responses.
- When discussing cooking methods, always link the method to the desired sensory or nutritional outcome.
- Ensure you can explain the 'why' behind food safety rules, not just the 'what'.
- Practice drawing links between the chemical properties of ingredients and the results of practical experiments.
- Use the provided stimulus material in Section A to ground your scientific explanations.
Common Misconceptions & Mistakes to Avoid
- Confusing the different methods of heat transfer.
- Failing to link chemical changes (e.g., coagulation) to the specific ingredient being used.
- Inaccurate use of technical terminology regarding food science.
- Lack of detail when explaining the causes of food spoilage.
- Inability to justify why a specific cooking method was chosen to conserve nutritional value.
Examiner Marking Points
- Understanding of heat transfer: conduction, convection, and radiation.
- Knowledge of functional and chemical properties of ingredients: gelatinisation, dextrinisation, shortening, aeration, plasticity, emulsification, coagulation, foam formation, gluten formation, denaturation, enzymic browning, and oxidisation.
- Ability to explain why food is cooked: digestion, taste, texture, appearance, and safety.
- Understanding of microbiological food safety: storage, date-marks, growth conditions of bacteria/mould/yeast, and cross-contamination prevention.
- Knowledge of food preservation methods: jam making, pickling, freezing, bottling, vacuum packing.
- Ability to remedy failed results (e.g., lumpy sauce, sunken cake).
- Understanding of the positive use of microorganisms in food production (e.g., cheese, yoghurt, fermentation).