Oncom is very popular in West Java, Indonesia. It is less well-known outside of Indonesia and is not as widely available internationally as tempeh. It is traditionally made from by-products of soybean processing and usually mixed with other ingredients like peanut press cake.
With 75 g black oncom starter you can make about 25kg of final oncom. This oncom starter has a shelf life of 1 year and contains only rice and rhizopus oligosporus spores. It is suitable for vegetarians and vegans.
This oncom starter can also be used as soy-free tempeh starter to make soy-free tempeh, because it contains no soy and grows well on non-soy substrates, such as grains, lentils, peas and other legumes. It can produce black spots after about 24 hours of fermentation, hence the name black oncom starter.