Food Spoilage (AQA GCSE Food Preparation & Nutrition)
Revision Note
Written by: Naomi Holyoak
Reviewed by: Lára Marie McIvor
The signs of food spoilage
Food spoilage can occur due to the action of:
enzymes
microorganisms, such as:
mould
yeast
bacteria
Signs of food spoilage due to enzymic action
Sliced fruit may turn brown due to oxidation on exposure to air; this is known as enzymic browning, e.g.
apples
pears
Enzyme activity can result in fruits becoming overripe, e.g.
bananas
avocado
Jason Thibault, via Flickr
Signs of food spoilage due to mould growth
Moulds are fungi that spread by the growth of thread-like filaments; moulds can grow in conditions that include:
acid or alkaline
high sugar
high salt
moist or quite dry (e.g. on hard cheeses)
warm temperatures
Moulds often grow on foods such as:
bread
cheese
jam
fruit
Visible mould can be green, black or white in colour and may have a furry appearance
Mould that is visible on the surface of food is a sign that microscopic moulds are present within the food
NotFromUtrecht, via Wikimedia Commons
Signs of food spoilage due to yeast
Yeasts are single-celled fungi; growth conditions include:
either in the presence or absence of oxygen
high enough moisture levels
warm temperatures
Yeasts often grow on or in acidic, sweet foods such as:
fruit, e.g. grapes, strawberries and tomatoes
fruit juice, e.g. orange juice
honey
jam
sweetened yoghurt
Yeasts that grow in the absence of oxygen can ferment the sugars in food; signs of this include:
gas bubbles that contain carbon dioxide forming on the surface of liquids
an alcoholic taste
a slightly fizzy mouthfeel
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