Oncom is one of the staple foods of Indonesia. In Indonesia, there are two kinds of oncom: red oncom and black oncom. Oncom is closely related to tempeh; both are foods fermented using molds, traditionally made in Indonesia. Oncom is particularly associated with West Java.
Oncom is made from the sediment left behind as a by-product form other foods -- soy bean sediment when making tofu, peanut sediment left when extracting peanut oil, cassava sediment when extracting the starch (pati singkong), coconut sediment left after extracting coconut milk.
Red oncom is made by using the mold Neurospora sitophila; it is the only human food produced by Neurospora species.
Black oncom is made by using the mold Rhizopus oligosporus.
In the production of oncom, sanitation and hygiene are important to avoid contaminating the culture with bacteria or other fungi like Apergillus flavus (which produces Aflatoxin). The molds used, Neurospora sitophila and Rhizopus oligosporus, are identified to be able to reduce the aflatoxin produced by Apergillus flavus.
While it is known that soya beans are the best substrate for growing R. oligosporus to create tempeh, oncom has not been as thoroughly studied; the best types of sediment for producing oncom are not yet known.
- "Production of High-Quality Oncom, a Traditional Indonesian Fermented Food, by the Inoculation with Selected Mold Strains in the Form of Pure Culture and Solid Inoculum", D. D. Sastraatmadja et al., J. Grad. Sch. Agr. Hokkaido Univ., Vol. 70, Pt. 2: 111-127 (2002), at