Decomposition and food preservationSpec 9.17B
Food goes bad because microorganisms (bacteria and fungi) feed on it, grow and respire. The rate of decomposition depends on temperature, water content and oxygen availability. Food preservation slows decomposition by changing these conditions.
| Factor | Effect on decomposition | Preservation method |
|---|---|---|
| Temperature | Warm conditions speed up enzyme reactions in microorganisms, so decomposition is faster. Cold slows these reactions. | Fridges and freezers keep food cold. Heating (for example in canning) kills microorganisms. |
| Water content | Microorganisms need water to grow and reproduce. Less water means slower decomposition. | Drying, or adding salt or sugar, which draws water out of microorganisms by osmosis |
| Oxygen | Most decomposers need oxygen for aerobic respiration. Less oxygen means slower decomposition. | Vacuum packing removes oxygen, and sealed cans keep oxygen out |