4.1.1

Microorganisms & Signs of Food Spoilage

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Microorganisms

Yeasts, moulds and bacteria are all examples of microorganisms. Pathogenic (disease causing) microorganisms can cause someone to suffer from food poisoning and cause food to go off.

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Conditions for growth and multiplication

  • Food.
  • Warmth.
  • Moisture.
  • Optimal pH.
  • Time (bacteria tend to split every 10-20 minutes).
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Slowing or stopping growth

  • Factors to change for controlling microorganism growth:
    • pH - e.g. pickling food as the vinegar will alter the pH.
    • Time - prepare food as quickly as possible and chill after preparation.
    • Water availability - e.g. salting food as the salt will absorb some of the moisture.
    • Temperature - e.g. putting food in a fridge to cool it.

Moulds and Yeasts

Yeasts and moulds are examples of fungi. Just like other microorganisms, they'll rapidly grow and multiply if the conditions are right.

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Moulds

  • Moulds can alter the appearance, smell and flavour of foods, like fruit, cheese and bread.
  • Mould is a furry growth, so it's very visible on foods.
  • Moulds excrete waste products that can give a person food poisoning. Toxins may stay on foods even after the mould has been wiped off.
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Yeasts

  • Fruits like plums and strawberries often develop yeasts on their surfaces.
  • Yeasts ferment the sugars in fruits and convert them into carbon dioxide and alcohol.

Jump to other topics

1Food Preparation Skills

2Food, Nutrition & Health

3Food Science

4Food Safety

5Food Choice

6Food Provenance

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