Most foods degrade and decay over time due to reactions with oxygen, decomposition of the food’s structure or flavour compounds, or microorganisms (or “microbes”) causing the food to spoil. The result can be food that is rancid, smelly, slimy, has lost its colour or flavour, or is growing things like mould.
We apply our understanding of spoilage mechanisms to extend the shelf life of foods by slowing the rate of spoilage. We exclude oxygen by packaging, slow reaction rates by refrigerating, gently heat foods (blanching, pasteurisation) to stop enzymes and to kill microbes. Nonetheless, as consumers we want “fresher”, more natural foods but many fresh and lightly preserved foods will degrade quickly.
Food quality can deteriorate before we perceive obvious signs of spoilage. If allowed to grow to high levels, some microbes that may contaminate foods (collectively called “pathogens”) can cause foodborne illness, or “food poisoning”. Often these microbes don’t visibly spoil the food so we can’t tell if a food has become unsafe.
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