Tempeh is mold
There is different fermentation processes : mold (aerobic), yeast and bacteria (anaerobic). Tempeh is part of the mold fermentation. The use of mold to ferment tempeh can be compared to the use of yeast in the bread making.
You are more familiar with molds that you think. Humans have a long tradition of eating molds in all over the world. In the West, the most familiar mold ferments are cheeses.
Tempeh is made by growing mold usually on soybeans but it can be made from any local legume such as lentils, chickpeas, black beans or peanuts. The mold of tempeh is actually the mycelium (the white hyphaes) that are the roots of a specific fungus called Rhizopus Oligosporus.
Tempeh is plant protein-rich
During the fermentation, the fungus feeds on the soybeans and grows in the space around them, binding them together with pure white molds (mycelium). This processs breaks down the molecules of the beans and this pre-digestion allows us to absorb many more nutrients from them. That makes tempeh as rich in protein and iron as meat. It is also higher in fibre and calcium while being lower in saturated fat and salt.
Tempeh was discovered in Indonesia (more precisely from Java island) hundred of years ago as a cheap alternative to meat, but more recently tempeh has been adopted by the vegan communities all over the world for its great properties. In the West, tempeh is already well known in the United States and the tempeh-loving community is growing in Europe. We personally discovered and felt in love with tempeh when we lived in Amsterdam. Since Indonesia is a former colony of the Netherlands, tempeh was well represented in grocery shops or street food shops. We then got interested and learned a lot about the super powers of tempeh (and other ferments) from Deshima/ Kushi Institute.
Since then, we aim to promote this plant protein-rich superfood (aka tempeh) as a key solution to the climate crisis, but also as a key solution to malnutrition.