The primary purpose of proper storage is to prevent food from spoiling. There are three main agents that cause food to deteriorate: moulds, yeast, and bacteria. Although they all act quickly on all foods containing moisture, each has its own characteristics.
Moulds are easily detected by their bluish-green colour and hair-like fungal structure. Mould commonly grows on bread, fruit, and cheese when these items are stored in a warm, dark, and slightly moist environment.
Yeast are plant micro organisms that are present in the air at all times. In order to grow and reproduce, yeasts require air, a source of food, and warm temperatures. Yeasts cause fruit and vegetables to ferment and rot by changing the natural sugars of the fruit into alcohol and carbon dioxide. This process of fermentation is used deliberately to make wine and beer, and the production of carbon dioxide during fermentation causes bread dough to rise. Yeasts can be detected by the formation of slime in the foods in which they are present.
Bacteria, although they are usually the first agents to begin the decomposition process, are the hardest to detect. Their presence usually only becomes noticeable after decomposition has advanced to the stage where unpleasant odours are produced.
When food is deteriorating, you will notice changes in its colour, odour, and taste. Examples include:
- Fruit goes soft, gets darker, and quickly rots.
- Vegetables start wilting and then become slimy and rotten.
- Butter, cheese, and dairy products get darker and develop a sour smell.
- Eggs become darker and acquire a foul aroma.
- Meat changes gradually at first, but then becomes darker and begins to smell “off.”
- Slime and mould appear.