Fermentation

You know that tempeh is a fermented food, but what exactly is fermentation? The scientific meaning of fermentation is the energy-producing anaerobic metabolism of a nutrient, such as sugar, without oxidation. Fermentation converts these nutrients primarily into lactic acid, acetic acid, and ethanol.

These are the fermentation end products of some microorganisms:

Saccharomyces: ethyl alcohol and carbon dioxide
Streptococcus and Lactobacillus: lactic acid
Propionibacterium: propionic acid, acetic acid, and carbon dioxide
Escherichia coli: Acetic acid, lactic acid, succinic acid, ethyl alcohol, carbon dioxide, and hydrogen
Enterobacter: formic acid, ethyl alcohol, 2,3-butanediol, lactic acid, carbon dioxide, and hydrogen
Clostridium: butyric acid, butyl alcohol, acetone, isopropyl alcohol, carbon dioxide, and hydrogen

In a broader sense, fermentation refers to the growth of microorganisms on food. It does not distinguish between aerobic (using oxygen) and anaerobic (not using oxygen) metabolism. We will use this broader meaning of fermentation here. Fermentation will gradually change the characteristics of the food through the action of enzymes produced by some bacteria, molds and yeasts.

Fermented soy products are very healthy and are available in several forms: miso, tempeh and natto. Other types of fermentation are lactic-fermentation, alcohol-fermentation and acetic-fermentation.

Safety of fermented foods

Fermented foods have a very good safety record, even in developing countries where food is produced under poor hygienic conditions. Fermented foods are overgrown with desirable and edible microorganisms, reducing the risk of contamination with pathogens such as Salmonella and Clostridium. Tempeh fermentation creates ideal conditions for the Rhizopus mold: relatively dry substrate, low pH, and high levels of Rhizopus spores. The low pH of the soybeans is achieved by natural lactic acid fermentation in the soaking water or by artificial addition of acids (lactic or acetic) after soaking.