Oncom
Oncom is a fermented food which is one of the traditional staples of the Sundanese cuisine of Indonesia. There are two kinds of oncom: red oncom and black oncom. The food is closely related to tempeh; both is fermented using mold.
Usually, oncom is made from the by-products of the production of other foods: soy pulp left over from making tofu, peanut press cake residue after the oil has been pressed out, cassava tailings after extracting the starch, coconut press cake remaining after the oil has been pressed out or when coconut milk has been produced. Since oncom production uses by-products to make food, it increases the economic efficiency of food production.
Black oncom is made by using Rhizopus oligosporus while red oncom is made by using Neurospora intermedia var. oncomensis. It is the only traditional human food produced from Neurospora.
Red oncom has been found to reduce the cholesterol levels of rats.
Toxicity
In the production of oncom, sanitation and hygiene are important to avoid contaminating the culture with bacteria or other fungi like Aspergillus flavus. Neurospora intermedia var. oncomensis and Rhizopus oligosporus reduce the aflatoxin produced by Aspergillus flavus. However, aflatoxin-producing molds are often naturally present on peanut press cake. Furthermore, coconut press cake can harbor the very dangerous Burkholderia gladioli, which produces two highly toxic compounds – bongkrek acid and toxoflavin. William Shurtleff and Akiko Aoyagi address toxicity in their .While it is known that soybeans are the best substrate for growing R. oligosporus to produce tempeh, oncom has not been as thoroughly studied; the best fermentation substrates for producing oncom are not yet known.