The Best of Indonesian Food (Oncom)

Red oncom

Oncom ("on-chom") is one of the traditional staple foods of West Java, 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, as is blue cheese.

Usually oncom is made from the by-products from the production of other foods -- soy bean sediment (okara) left from making tofu, peanut presscake left after the oil has been expressed, cassava sediment when extracting the starch (pati singkong), coconut presscake remaining after oil has been expressed or when coconut milk has been produced.

Because oncom production uses these potential waste streams to make food, oncom production increases the efficiency of human nutrition in unique ways, and in a world with ever-increasing hunger and ever-dwindling cropland, this carries great promise for those of us who could most use help.

Red oncom also reduces cholesterol levels of rats, suggesting effects in humans.

Red oncom is made by using the mold Neurospora intermedia var. oncomensis; it is the only human food produced by Neurospora species.

Black oncom is made by using the mold Rhizopus oligosporus.

Toxicity

In the production of oncom, sanitation and hygiene are important to avoid contaminating the culture with bacteria or other fungi like Aspergillus flavus (which produces aflatoxin). Neurospora intermedia var. oncomensis and Rhizopus oligosporus reduce the aflatoxin produced by Aspergillus flavus. However, aflatoxin-producing molds (Aspergillus spp.) are often naturally present on peanut presscake and coconut presscake can harbor the very dangerous Pseudomonas cocovenenans, which produces two highly toxic compounds - bongkrek acid and toxoflavin. Thus careful attention to sanitation during oncom (and tempeh) production may not be sufficient to ensure the safety of the final product.

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.