Yeasts can cause foods to ferment. They are destroyed, however, at temperatures between 140 degrees F and 180 degrees F. Bacteria grow and multiply rapidly on food. Each type of bacteria varies as to the temperatures at which it can grow. They may grow at cold, warm or hot temperatures. Some bacteria need oxygen to grow, others don't.
Most bacteria grow best on low acid foods, such as vegetables or meats.
Most bacteria are destroyed by heat. Physical changes also cause food to spoil. Bruising and punctures not only physically damage the food, but in fruits and vegetables, for example, they also provide places where microorganisms can start to grow. Water loss and wilting are other physical ways food spoils. Enzymes are the substances in foods that help them grow and mature.