Pronunciation - Tempeh [tem-pay] in the west, and Tempe [tèm-phè] in Indonesia.
Tempeh is a staple food in Indonesia, where it is traditionally prepared with soy beans or a certain variety of peanut fermented with mold, Rhizopus oligosporus. The cultured soybeans or nuts are bound together by a thick white mycelium of new mold-growth, to form a cake. Although in some western countries, a variety of legumes and cereal grains are sometimes used to prepare tempeh, soy bean is the common legume used in the preparation of tempeh.
Fresh tempeh has an earthy aroma, resembling a cross between mushrooms and fresh yeast. Deep-fat-fried tempeh [tempeh goreng] fried in coconut oil, is widely consumed in Indonesia. Tempeh goreng has a delicious slightly nutty flavour with subtle mushroom-like overtones. The texture of tempeh goreng has a desirable mouth feel. In Indonesia, tempeh based dishes are prepared in a variety of ways to create many wonderful nutritious meals. Tempeh is also used in a variety of dry food products. One product in particular, Tempeh Krupuk [kroo-pook], is similar to prawn chips, but which includes small pieces of tempeh distributed throughout each fluffy crisp-chip.
Traditional tempeh is said to be rich in Vitamin B-12 and natural antioxidants. One antioxidant in particular bio synthesized by organisms, is referred to as factor 2, which is said to be 600 times more potent than Vitamin E. Some three natural occurring antibiotics produced by the mold have been discovered in tempeh. Some of the B group vitamins increase in comparison to unfermented soybeans. Tempeh also contains enzymes and free amino acids. Vitamin B-12 found in Indonesian tempeh is believed to be bio synthesized by a non pathogenic strain of Klebsiella pneumoniae and quite possibly, there are other strains of organisms which produce Vitamin B-12 in symbiosis with molds and other bacteria during the tempeh fermentation process. Research suggests that the Vitamin B-12 of tempeh is the bio-active form, while other research suggests that it is the analogue [non bio-active form]. The bio synthesis of the particular form of Vitamin B-12, may depend on the culture and culture-conditions e.g., traditional procedure Vs commercial methods.
Traditionally, tempeh is prepared by initially boiling whole dry soybeans in fresh water. The heat source is removed and the beans are left to stand for approximately 16 hours. A natural fermentation process acidifies the beans. The soy beans are taken to a local river and the beans are placed in large woven bamboo basket. The baskets are submerged in shallow waters. The soy beans are then stomped under the feet, similar to squashing grapes in traditional wine making of former days. However, in this case, the procedure is performed to de-hull the beans, and the water current simultaneously takes away the floating hulls. The de-hulled soybeans remaining in the basket, are boiled for approx. 60 minutes in fresh water to partially cook the soybeans. The beans are strained, cooled and excess moisture is removed by spreading the beans over a table. Biang ragi [mother-culture], consisting of mold spores mainly from the Rhizopus oligosporus species, is mixed well with the beans to inoculate. Fresh banana leaves, which are pierced with long needles, to from small holes throughout the leaves, are first laid down on the surface of a table, rendered from lengths of bamboo strips. The inoculated soy beans are spread over the banana leaves to form approx. 10 cm [4 inch] layer. More pierced banana leaves are laid over the beans to seal the bed of inoculated soybeans and then weights are placed over the leaves, ensuring that the leaves are in direct contact with the inoculated beans.
After a 24 hour fermentation at room temperature at approx. 30° to 32°C [86° to 90° F], the soybeans become covered with a rich white mycelium, due to vigorous mold growth. The mold binds the beans together, forming a large bed of beans as a cake of fresh tempeh. The tempeh is cut into small workable pieces, which are ready for consumption, or sold at a local market. Heat is naturally generated during the maturation process, making tempeh a unique culture-food product. So when a fresh piece of tempeh is held, it feels warm with evidence of life.
Through modern intervention, today, perforated plastic bags are used to ferment tempeh replacing the banana-leaf technique of former days. Although, smaller tempeh producers may still use the lauru contact-leaf method, to inoculate partially cooked soy beans or peanuts, modern starter-cultures are often employed instead.