Food Chemistry and Nutrition Basics
2. Food Chemistry and Nutrition Basics
This domain checks your grasp of the chemical components of food, their reactions during processing, and basic nutrition labelling. Questions often ask you to classify nutrients, explain browning or rancidity, and calculate energy from macronutrients.
Core rules
- Water is the largest component of many foods; water activity (aw) predicts microbial growth better than moisture content alone.
- Carbohydrates include sugars, starch and fibre; starch gelatinises on heating with water and retrogrades on cooling.
- Proteins denature on heat, acid or shear; enzymes can cause browning or softening and may be inactivated by blanching.
- Fats oxidise (rancidity), especially with heat, light, metals and oxygen; antioxidants slow this.
- Micronutrients are vitamins and minerals. Fat-soluble vitamins A, D, E and K; water-soluble B-complex and C are heat-labile.
- Maillard browning occurs between reducing sugars and amino groups; caramelisation is sugar-only browning.
Worked example
A 100 g snack contains 10 g protein, 20 g carbohydrate, 5 g fat and 2 g fibre. Using Atwater factors (protein 4, carbohydrate 4, fat 9, fibre 2 kcal/g): energy = (10×4) + (20×4) + (5×9) + (2×2) = 40 + 80 + 45 + 4 = 169 kcal per 100 g. Reasoning: multiply each gram value by its factor, then sum; do not count water or ash.
Traps
Do not use 9 kcal/g for carbohydrate. Maillard needs protein or amino acids, so it is not caramelisation. Water activity is not the same as percentage moisture. Vitamin C losses are not due to fat oxidation.