Food Science
The Food Science domain tests the composition of foods and the physical, chemical and biological changes they undergo during storage, preparation and preservation. Questions often ask you to explain why a recipe behaves as it does, or to choose a preservation method and justify it.
Spoilage
Food spoils through microbial growth (bacteria, moulds, yeasts), enzyme action (browning, ripening), chemical oxidation (rancidity) and physical damage. Controlling moisture, temperature, pH, oxygen and time slows all four.
Preservation
- High temperature: pasteurisation (63 °C for 30 minutes, or 72 °C for 15 seconds), sterilisation/canning, drying.
- Low temperature: refrigeration slows microbes; freezing stops growth but does not kill them.
- Removal of moisture: sun drying, dehydration, addition of sugar or salt.
- Chemical: vinegar, benzoic acid, sulphur dioxide; fermentation (curd, idli batter).
- Irradiation and modified atmosphere packaging.
Cooking changes
Starch gelatinisation needs heat and water; dextrinisation occurs on dry heating of starch; caramelisation is sugar browning; the Maillard reaction needs sugar plus protein and gives the brown crust of baked foods; protein coagulates on heating (egg white).
Worked example. Lemon juice curdles hot milk. Acid lowers the pH to the isoelectric point of casein (about pH 4.6), where the protein carries no net charge, repels less and clumps. Reasoning with pH, not "sourness", earns the mark.
Traps. Caramelisation is not Maillard browning; freezing preserves but does not sterilise; pasteurisation does not make milk sterile; and gelatinisation is not the same as gelation.