Microorganisms & Signs of Food Spoilage
Food Preparation & Nutrition: AQA GCSE, topic 4.1.1
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.
Conditions for growth and multiplication
- Food.
- Warmth.
- Moisture.
- Optimal pH.
- Time (bacteria tend to split every 10-20 minutes).
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.
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.
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.
Test yourself on Microorganisms & Signs of Food Spoilage
What type of organisms are yeasts, moulds and bacteria?
What conditions are important for the growth and multiplication of microorganisms in food?
What type of organism are yeasts and moulds?
What does yeast convert the sugars in fruits into?
Which foods are more likely to go mouldy?