Mould is a type of fungus, typically characterised by visible white or green dust-like spots that grow on the surface to foods. They are often found on meat or poultry, as well as fruits and vegetables. Yeast is a single-celled fungus that breaks down carbohydrates into carbon dioxide and alcohol (fermenting them). They are characterised as pale brown colonies on fruit and are often found in yoghurts, fruit juices and fruits.