Oncom (IPA: ɔnˈtʃɔm) is a fermented food which is one of the traditional staples of the Sundanese cuisine of Indonesia.

[3] 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).

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 book section on oncom.

[5] Oncom is also a selected filling for comro, lontong and arem-arem rice dumplings.