Fermentation
Tempeh is a fermented food. So what is
fermentation exactly?
The scientific meaning of fermentation is the energy-yielding anaerobic metabolism of a nutrients, such as sugars, without oxidation. Fermentation converts these nutrients mainly into lactic acid, acetic acid, and ethanol.
These are fermentation end product 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 meaning, fermentation refers to the growth of microorganisms on food. Here no distinction is made between aerobic (oxygen is used) and anaerobic (no oxygen is used) metabolism. We will here use this broader meaning of fermentation. Fermentation will gradually change the characteristics of the food by the action of enzymes, produced by some bacteria, molds and yeasts.
Safety of fermented food
Fermented foods have a very good safety record, even in developing countries where food is produced under poor hygienic conditions. Fermented foods are overgrown by desirable and edible microorganisms, thereby reducing the risk of contamination with pathogens such as salmonella and Clostridium. During the tempeh fermentation ideal conditions are created for the
Rhizopus mold: rather dry substrate, low pH and high amounts of
Rhizopus spores. The low pH of the soybeans is obtained by a natural lactic acid fermentation in the soaking water or by an artificial addition of acids (lactic or acetic acid) after the soaking process.
