Tempeh/Tempe is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form.
It originated from Indonesia, invented by the Javanese, where it is most popular, although it is common in other parts of Southeast Asia as well, introduced by migrated Javanese.
It is especially popular on the island of Java, where it is a staple source of protein.
Like tofu, tempeh is made from soybeans, but tempeh is a whole soybean product with different nutritional characteristics and textural qualities. Tempeh's fermentation process and its retention of the whole bean give it a higher content of protein, dietary fiber and vitamins compared to tofu, as well as firmer texture and stronger flavor.
Tofu, however, has a higher concentration of protein per carbohydrates, and is thought to be more versatile in dishes. Because of its nutritional value, tempeh is used worldwide in vegetarian cuisine; some consider it to be a meat analogue.
Even long ago before people found and realized the rich nutrition fact of tempeh, tempeh was referred to as “Javanese meat.”
Tempeh begins with whole soybeans, which are softened by soaking and dehulled, then partly cooked. Specialty tempehs may be made from other types of beans, wheat, or may include a mixture of beans and whole grains.
A mild acidulent, usually vinegar, may be added in order to lower the pH and create a selective environment that favors the growth of the tempeh mold over competitors. A fermentation starter containing the spores of fungus Rhizopus oligosporus is mixed in. The beans are spread into a thin layer and are allowed to ferment for 24 to 36 hours at a temperature around 30°C (86°F). In good tempeh, the beans are knit together by a mat of white mycelia.
Under conditions of lower temperature, or higher ventilation, gray or black patches of spores may form on the surface -- this is not harmful, and should not affect the flavor or quality of the tempeh. This sporulation is normal on fully mature tempeh. A mild ammonia smell may accompany good tempeh as it ferments, but it should not be overpowering. In Indonesia, ripe tempeh (two or more days old) is considered a delicacy.