Desired chemical breakdown of a food by a microorganism (bacteria or yeast), and occurs when making foods such as bread, yogurt, sauerkraut, kimchi, or wine.
Fermentation is the term for yeast and bacteria converting sugar in foods to acid, gas, or alcohol. This process is used for a number of kinds of foods, such as:
- sauerkraut and kimchi
- wine and beer
One key characteristic about fermentation is that it is microorganism activity that does not render food unsafe to eat. Any questions about an undesired or dangerous change in foods due to microorganisms should be tagged with spoilage.