Food science and nutrition
Design & Technology · Key Stage 3 · The School
What heat does
DENATURING: protein unravels and sets — an egg white turning white and firm, permanently. GELATINISATION: starch granules absorb water and swell, thickening a sauce. CARAMELISATION: sugars brown above about 160°C. The MAILLARD REACTION between proteins and sugars gives roasted, baked and seared food its flavour and colour. Browning is not just colour; it is hundreds of new compounds.
What ingredients do
In a cake: flour gives structure (gluten), egg binds and enriches, sugar sweetens and holds moisture, fat shortens the texture and carries flavour, raising agent produces gas so it rises. Remove any one and something specific breaks. That is why substitutions in baking rarely work by guesswork.
Spoilage
Bacteria need warmth, moisture, food and time. The DANGER ZONE is roughly 8°C to 63°C, where they multiply fastest — which is why food is kept below or above it, not between. Chilling slows them, freezing stops them without killing them, and thorough cooking destroys most. Preservation methods all remove one of the four things bacteria need.
Mix flour and water and knead for five minutes: it goes from crumbly to stretchy and elastic, because kneading develops GLUTEN — which is what gives bread its structure. Now heat cornflour in cold water and stir as it warms: at around 60 to 70 °C the starch granules absorb water, swell and burst, and the liquid suddenly thickens. That is GELATINISATION, and it is why a sauce thickens all at once rather than gradually.