Food Science
What this domain tests
Food science asks why food behaves as it does during preparation, cooking and storage - the chemistry and physics behind a method, not just the recipe steps.
Core rules
- Heat transfer: conduction (pan base), convection (fan oven, boiling water), radiation (grill, microwave - microwaves excite water molecules).
- Protein first denatures (structure unfolds through heat, acid or whisking), then coagulates (sets). Overheating causes syneresis, the weeping of liquid.
- Starch gelatinises between about 60 and 80 °C: granules absorb water, swell and amylose leaches out, thickening the liquid. Dry heat causes dextrinisation (browning, shorter chains). Cooling causes retrogradation, seen as staling.
- Sugars caramelise alone from about 160 °C. Maillard browning needs a reducing sugar plus an amino group, a dry surface and heat above about 140 °C.
- Emulsions: oil-in-water (mayonnaise, with lecithin from egg yolk as emulsifier) and water-in-oil (butter). Stability comes from small droplets plus an emulsifier.
- Others: aeration (egg-white foam, stabilised by acid and sugar), gluten development by kneading, enzymic browning by polyphenol oxidase (blocked by acid, heat or blanching), pectin gelation (sugar plus acid).
- Nutrient retention: water-soluble vitamins leach, and vitamin C is heat- and oxygen-labile - use little water, cook briefly, keep the lid on.
Worked example
Why a white sauce stays thin. The roux must cook long enough for fat to coat every flour granule; liquid is then added gradually with stirring so granules separate and hydrate. Boiling hard for a long time shears the swollen granules so the sauce thins, and adding dry flour to hot liquid clumps. A 1 flour : 1 fat : 10 milk ratio gives a coating sauce.
Traps that cost marks
- Confusing caramelisation (sugar only) with Maillard (sugar plus protein).
- Saying denaturation "kills" protein, or placing coagulation before denaturation.
- Claiming salt speeds yeast - it slows it by osmosis.
- Over-whisking egg whites after sugar is added, giving a grainy, unstable foam.