Oncom (by F.G. Winarno)

A. Product knowledge

Oncom or Onchom is very popular traditional fermented foods particularly in West Java of Indonesia. Although it has been consumed for centuries, biomodifications which contribute to nutritional and organoleptic changes during fermentation are far from being understood.

As a food, oncom is not only interesting, but also important fermented food product in Indonesia. It is interesting because the fermentation is carried out utilizing microbial starter of Neurospora sitophila. As far as we know, Neurospora is not utilized any where else in the world for preparing any food.

The fermented product in the form of a cake are orange pink in colour due to the colour of its conidiospores, which were form on the surface of the cake or finish product.

Oncom is a specific food in West Java and traditionally can be used as raw material in various Indonesia dishes or preparations served as fried or cooked (Gejos oncom, keripik oncom, oblok-oblok oncom, oncom goreng tepung, pepes oncom, sambel oncom, , tauge goreng, dan tumis kangkung oncom, serta tumis oncom).


The raw material used for oncom preparation principally consist of peanut prescake but sometimes mixed (adulterated) with tapioca prescake (onggok) or tofu prescake. The purpose of adding other raw material is to get better texture, despite despite also to increase volume and weight. If the raw material only consist of purely peanut prescake the texture usually is very tough.

Some local people also used tapioca prescake or tofu prescake only as raw material. Strain of  Neurospora sitophila used in this fermentation are quite active in producing enzymes lipase (digesting lipid or fat) and protease (digesting protein) If the fermentation process conducted only utilizing Neurospora sitophila, the final product will appear orange pink colour (called red oncom). However beside Neurospora sitophila oncom may be produced by utilizing other mold (fungi) ie .. Rhizopus oligosporus, or in the combination with Neurospora sitophila. since Rhizopus oligosporus producing black spores or conidiospores on the surface of the product will appear black colour (black oncom) with some dots of orange sport:

B.Method of Preparation

Peanut prescake (or other materials) was soaked in water for 24 hours until become soft. During the soaking period the fatty substance will float at the surface .

The fat was scrapped and discarded, washed to avoid any extraneous and dirt. Drain and added tapioca prescake with ratio of 5 to I, mixed and steamed for ¾ to 1,5 hours or until the product cooked. At the end of cooking colour become brown or grey.

The product then molded or shaped in tin or wooden box, 2 cm thickness and wrapped in banana leaves. After it is cool then incubated with mould starter either with Neurospora  sitophila or and Rhizopus oligosporus. The final preparation was then incubated or fermented at room temperature for 24 hours.

C. Nutrition Value

The chemical composition of black oncom and red oncom varied depend on the nature of the raw material used as substrate. The black oncom using peanut prescake having nutrition composition as follows: 57 percent moisture , 13 percent protein, 6 percent of fat, and 22 percent carbohydrade.

By the activity of enzyme produced by the mold, the protein content in the raw material of oncom was hydrolyzed and degraded into amino acids, the lipase hydrolyzed the fats and glycerol into fatty acids and glycerol. While the carbohydrate, with the activity of amylase kits and other carbohydrate degrading enzymes hydrolyzed the carbohydrates into simple sugars, alcohol or some esters. Which later those compounds will contribute to specific flavour to the oncom.

The optimum temperature for development of characteristic flavour, texture, aroma, and colour is 25º to 30º C.

This particular mold produced orange to orange pink condiospores, this final product having very particular attractive colour. Rhizopus oligosporus  the mold traditionally used to ferment soybean in the preparation of tempe, it produced black spores, resulting in ash-grey coloured oncom, locally known as black oncom.

The flavour of oncom has been described as fruity and somewhat alcoholic, however fried product takes on a mince - meat or almond flavour. The accumulation of free amino acids and peptides in fermented peanut prescake result in the meaty flavor characteristic of other fermented oilseed product.

Van Veen and Schaefer (1950) speculated on the beneficial of tempe on prisoners of war suffering from dysentery. Certain strain of Rhizopus oligosporus are known to produce an antibacterial compound especially active against some Gram positive organims (Wang et al 1969).

This antibacterial activity may be significant for those people whose diet are often nutritionally inadequate. The suggested suppression of intestinal bacterial due to the consumption of tempe (as well as oncom) by people of young ages may well have been due to the presence of anti metabolites secreted by Rhizopus oligosporus.


SUMMARY

Oncom is unique food product consume by many people population of Indonesia and consider delicacy by local people, and have been used for various food preparation and local dishes. Oncom have some beneficial affect against or suppression of intestinal undesired bacteria, particularly for local people where diet are often nutritionally inadequate. The per capita consumption of oncom seem destined to increase in the future, particularly in light of increasingly significant cost advantages in producing food practice in plant versus animal origin.