Fermentation is a metabolic process converting sugar to acids, gases and/or alcohol using yeast or bacteria. In its strictest sense, fermentation is the absence of the electron transport chain and takes a reduced carbon source, such as glucose, and makes products like lactic acid or acetate. No oxidative phosphorylation is used, only substrate level phosphorylation, which yields a much lower amount of ATP. Fermentation is also used much more broadly to refer to the bulk growth of microorganisms on a growth medium. The science of fermentation is known as zymology.
In the food context, fermentation is a process in which microorganisms, such as bacteria, yeast, and fungi, break down carbohydrates and convert them into other compounds, such as alcohol, organic acids, and gases. This process can transform the flavor, texture, and nutritional value of foods, and is used in many cultures around the world to create unique and delicious dishes.
Some examples of fermented foods include:
- Yogurt: Made from fermented milk, yogurt contains beneficial bacteria known as probiotics that can improve gut health.
- Kefir: A fermented milk drink that is similar to yogurt, kefir is also rich in probiotics and has a tangy flavor.
- Sauerkraut: A traditional German dish made from fermented cabbage, sauerkraut is high in vitamins C and K and has a distinctive sour taste.
- Kimchi: A Korean staple made from fermented cabbage and other vegetables, kimchi is spicy, tangy, and packed with probiotics.
- Miso: A Japanese seasoning made from fermented soybeans, miso is rich in umami flavor and can be used in soups, marinades, and dressings.
- Tempeh: A vegetarian protein source made from fermented soybeans, tempeh has a nutty flavor and a meaty texture.
Other examples of fermented foods and beverages include kombucha, sourdough bread, pickles, cheese, beer, and wine.
Fermentation is similar to other processes that involve the breakdown of food compounds by microorganisms, such as pickling, curing, and aging. However, these processes may involve different types of microorganisms, different ingredients, or different methods of preparation, and can result in different flavors and textures in the final product.