FermenteaWhere food goes to change
Traditional method
oncom hideung · oncom hitam
Black oncom is a mould-fermented cake made from defatted peanut cake, pressed to about 2 cm, steamed and then incubated for a day at ambient temperature.
Black oncom is a fermented food traditionally made from the solid residue remaining after peanuts have been pressed for oil.
The residue, or defatted peanut cake, still contains substantial protein, carbohydrates and other nutrients. A mould culture grows through it, transforming the material into a coherent cake with a distinctive flavour and texture.
The Indonesian name is oncom hitam; in Sundanese it is also called oncom hideung, meaning black oncom.
The term black describes the customary category and characteristic appearance. The product may show pale, grey or dark fungal growth depending on the culture and development.
Black oncom is particularly associated with Rhizopus species, including Rhizopus oligosporus, now frequently classified within Rhizopus microsporus.
Other black-oncom traditions include fungi from the genus Mucor.
This means that a visually similar cake does not necessarily contain an identical microbial population.
The preparation is closely related to red oncom in culinary context but differs in substrate and characteristic fungi.
Defatted peanut cake — 1 kg ratio basis
Starter — Approximately 2 g per kg raw material
Culture — Identified Rhizopus oligosporus preparation
Steaming — 45–90 minutes
Cake thickness — Approximately 2 cm
Fermentation — 24 hours
Temperature — Ambient; no numerical value supplied
Final yield — Not reported
Safety classification — High-risk research description; process validation required
The kilogram quantity is a normalization of the reported starter dose. It is not a documented experimental yield.
Black oncom belongs to the culinary culture of western Java, especially areas around Bogor and other Sundanese communities.
Its manufacture demonstrates the importance of turning byproducts of oil extraction into edible food.
Peanut pressing removes a proportion of the original oil, but leaves behind a material rich in protein and other solids.
Fermentation transforms its texture and flavour, making it useful in dishes rather than merely a residue of agricultural processing.
The exact historical invention date is not established.
A 2025 photographic study documented black-oncom production at Cimanggu 2 village in Bogor, emphasizing the continuity of family methods and the work of local processors.
This establishes a living production tradition at a specific location without proving when the technique first developed.
The process also resembles the production of tempeh in some respects.
Both may involve Rhizopus cultures and the binding of plant materials into cakes.
But black oncom is not simply tempeh made from peanuts.
Its principal raw material is defatted peanut residue, and its microbial communities and regional culinary identity can differ.
The starting material is the solid cake left after oil is extracted from groundnuts, Arachis hypogaea L.
It contains residual protein, fibre, carbohydrate and some fat.
Its composition depends on the quality of the peanuts and the oil extraction process.
Research summarizes protein values that can exceed one-third of dry matter for some defatted peanut-cake materials.
These figures are compositional examples, not guarantees for a particular commercial cake.
Food-grade peanut cake is essential.
Material intended solely for animal feed should not automatically be treated as suitable for human fermentation.
The original record specifies an identified starter associated with Rhizopus oligosporus at about 2 g per kilogram of raw material.
The culture grows across the prepared substrate and produces enzymes that modify its constituents.
The exact commercial preparation and viable spore count are not supplied.
Consequently, two grams of an arbitrary starter cannot be assumed microbiologically equivalent.
Water is used as needed to prepare the peanut cake for heat treatment and fungal growth.
The original record does not give an exact quantity.
Some West Javanese black-oncom methods incorporate cassava-processing residue to change texture.
This is a documented variant, not an ingredient specified in the original peanut-only formulation.
The moisture and carbohydrate composition of cassava residue can significantly change the fermentation.
It should not be added casually without an appropriately established process.
The record describes steaming equipment, a surface or mould for shaping the material and an area for incubation.
A clean, food-safe preparation environment is necessary.
The cakes are approximately two centimetres thick.
That dimension matters because fungal growth, oxygen access and internal temperature can vary through a thick mass.
The record gives no exact oxygen-control specification or validated temperature range for incubation.
This is a literature-derived preparation rather than a validated home recipe.
Begin with food-grade defatted peanut cake.
Check the material's source and storage history.
Do not use visibly mouldy, stale or contaminated peanut residues.
Peanuts are particularly important from a food-safety perspective because contaminated raw materials may contain aflatoxins.
Fermentation or cooking should not be assumed to eliminate those toxins.
Steam the peanut cake for 45–90 minutes.
The recorded method gives this range rather than one selected duration.
The purpose is to heat the substrate, modify its physical structure and reduce competing microorganisms.
The record does not state whether all materials in the reported range had identical thickness or initial moisture.
It is therefore not possible to select a universally appropriate time within that range.
Spread the prepared material into cakes approximately 2 cm thick.
Uniform thickness helps make conditions more consistent.
The original record does not give a standard length or width.
Allow the material to cool before adding the starter.
A numerical cooling temperature is not supplied.
The purpose is to avoid exposing the living culture to damaging heat.
Distribute approximately 2 g identified Rhizopus starter per kilogram of raw material.
The aim is to introduce the intended fungal culture throughout the substrate.
The process should not rely on an unidentified wild mould.
Hold the inoculated cakes at ambient temperature for 24 hours.
The published trial does not give a numerical ambient temperature.
Ambient conditions in Bogor differ from those in a cold European kitchen or a hot commercial production room.
The culture is expected to change the cohesion and structure of the cake.
But the recorded method does not establish a validated microbiological endpoint.
A cake should not be considered safe merely because visible fungal growth has appeared.
The final yield and storage interval remain unreported.
Rhizopus fungi produce hyphae that spread through the substrate.
These hyphae bind particles together.
The organism also secretes enzymes that can alter proteins, carbohydrates and lipids.
Peanut proteins are broken into smaller compounds.
The resulting peptides and amino acids influence taste and the accessibility of nutrients.
Some products develop a pronounced savoury flavour.
Fungal enzymes transform available carbohydrates.
If cassava residue is included, the additional carbohydrate may change growth and flavour.
Residual peanut oil may be affected by lipases and oxidation.
This can contribute desirable flavour complexity, but rancidity is a quality problem.
The surface appearance changes as fungal growth develops.
Some species produce darker spores as they mature.
Neither blackness nor whiteness is a reliable test of species identity.
The presence of a white fungal network is not proof that the cake contains only the intended organism.
A defatted cake differs from whole peanuts.
Removing oil changes the ratio of protein, carbohydrate and fat.
It also changes how the material absorbs water.
The mechanical structure of the pressed residue influences how it can be formed into cakes.
This is why direct substitution of whole peanuts or ordinary peanut butter would not reproduce black oncom.
A high-fat material can also present different conditions for microbial growth and oxidation.
Different oil-pressing methods may leave significantly different residual fat levels.
The recorded method does not supply a fixed residual-oil specification.
This is the form represented by the original record.
Peanut residue is the primary substrate, and Rhizopus is the named starter.
Some producers mix defatted peanut cake with cassava-processing residues.
The additional carbohydrates and different moisture properties can influence texture.
Some scientific reviews identify Mucor species alongside Rhizopus in black-oncom production.
This is a microbiological variation, not simply a change of seasoning.
Red oncom generally uses a Neurospora culture and often tofu residue.
It is treated separately because the principal process organism and typical substrate differ.
Black oncom is an ingredient in West Javanese home cooking.
It is usually cooked with aromatics rather than eaten as an isolated raw fermentation cake.
Nasi tutug oncom is rice mixed with seasoned, cooked oncom.
It is a familiar Sundanese dish, often served with vegetables, sambal and additional side dishes.
The oncom contributes savoury flavour and texture to the rice.
Seasoned oncom can be wrapped in banana leaves and cooked.
The filling may include chillies, shallots, garlic and aromatic leaves.
The wrapper helps contain the mixture and contributes its own aroma during heating.
Oncom can be broken into pieces and sautéed with chilli and other seasonings.
Some preparations dry or fry the material more extensively for a firmer texture.
Cooked oncom can be incorporated into chilli-based relishes.
It provides body and a fermented savoury character.
Peanut-derived foods require particular attention to aflatoxins.
Aflatoxins are toxic compounds produced by certain moulds, particularly some Aspergillus species.
They can contaminate peanuts before processing or during unsuitable storage.
An aflatoxin-contaminated peanut cake is not made safe simply by inoculating it with Rhizopus.
Normal steaming does not reliably remove these toxins.
This is one reason why the source and testing of the raw material matter.
A food-grade starter does not guarantee that competing microorganisms are absent.
Unidentified fungal growth should not be accepted based on colour or a vaguely familiar smell.
Moist nutrient-rich cakes can also support bacterial growth.
The incubation environment must be appropriately managed.
Black oncom made from peanut cake contains peanuts and must be treated as a peanut-allergen food.
Fermentation does not establish that peanut allergens have been eliminated.
The original record provides no validated finished storage interval.
Fresh oncom should be treated as perishable unless a manufacturer has established different storage conditions.
Weak binding may indicate poor fungal growth, unsuitable moisture, inappropriate temperature or poor culture viability.
Uneven growth may reflect inconsistent cake thickness or inoculum distribution.
Strong rancidity can indicate deteriorated peanut oil.
Visible unwanted mould, slime or putrid odours are grounds for rejection.
However, none of these sensory observations can reliably exclude aflatoxins or all microbial hazards.
The research describes what a traditional product can look like, not a complete home quality-control system.
The conversion of peanut-processing residue into edible protein-rich food is important.
It creates value from material that might otherwise be discarded or used for lower-value purposes.
Modern research into food-processing residues has renewed interest in oncom for precisely this reason.
However, sustainability cannot be separated from safety.
Using an inexpensive byproduct is beneficial only when the raw material is food-grade and the resulting fermentation is appropriately controlled.
Black oncom is described as a fermented defatted-peanut-cake product, distinct from okara-based red oncom; the cited source presents a general process description rather than a historical date.
Yield 1 kg peanut cake before starter (normalized ratio basis; source yield not reported) · Scaling: source ratios only
This is a moist mold-fermented cake, and a species name or surface color alone cannot establish the identity or safety of growth.
Hazard sourceUse only a traceable food-production Rhizopus starter and an independently reviewed process; do not identify or backslop wild mold by appearance.
Control sourceThis literature process is not professionally validated for home production. Do not treat visible mold, smell, taste, or heating as proof of safety.
The review associates oncom with West Java; the paper distinguishes peanut-cake black oncom from okara-based red oncom.
Red oncom is a West Javanese cake fermented from pressed soy pulp with a Neurospora starter, a little tapioca starch and vinegar. It is a different food from black oncom, made on another substrate with another mould.
An Indonesian savoury soybean paste built in two stages: cooked beans and roasted flour carry a mould fermentation, then mature in salt brine into a thick, salty seasoning.
This controlled study protocol makes Aspergillus koji from soybeans and then ferments it with 4% salt. It uses a 150 g jar batch and a defined moisture target; the research method is not a validated home process.
Japanese soybean koji: steamed soybeans, loose or formed into balls, grown over with Aspergillus mould to make the enzymes for mame-miso, tamari and regional soybean condiments.
A Chinese fermented soybean condiment from Chongqing and Sichuan, made by growing Mucor-type mould on cooked beans, then salting and maturing them into dark, savoury, soft beans with a concentrated aroma.
A two-cup soybean batch uses one Cultures for Health tempeh starter packet and vinegar. The supplier describes dehulling, a thin vented layer, controlled early incubation and attention to self-heating; it is not a validated home process.
Sufu, or furu, is Chinese fermented tofu: bean curd is salted and ripened, often after a mould stage, into a soft, creamy, intensely savoury condiment.
An Okinawan fermented tofu: dried tofu cubes matured in rice koji, awamori and salt, traditionally with red Monascus koji, until the curd turns smooth and intensely savoury.
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Journal of Food ScienceProcess · History
Umami fractions obtained from water-soluble extracts of red oncom and black oncom—Indonesian fermented soybean and peanut productsBlack oncom substrate is defatted peanut cake; the reported process steams raw material 45–90 min, forms 2 cm cakes, cools, inoculates at about 2 g/kg, and incubates 24 h at ambient temperature.
Cited in: What is black oncom?; Recipe at a glance; A West Javanese food tradition; Defatted peanut cake — 1 kg; Rhizopus starter — approximately 2 g; Water; Optional cassava residue; Equipment; Method: documented black-oncom process; Stage 1 — Inspect the substrate; Stage 2 — Steam; Stage 3 — Form cakes; Stage 4 — Cool; Stage 5 — Inoculate; Stage 6 — Incubate; Stage 7 — Assess; The microbiology of black oncom; Protein transformation; Carbohydrate metabolism; Lipid changes; Spore formation and colour; Why substrate composition matters; Peanut-cake black oncom; Peanut and cassava residue; Mucor-associated black oncom; Red oncom; How black oncom is eaten; Nasi tutug oncom; Pepes oncom; Fried or sautéed oncom; Sambal oncom; Unintended mould growth; Bacterial contamination; Allergens; Storage; Black oncom as a sustainable food
Journal of Agriculture and Food ResearchGeography · History
The nutritional and economic potential of tofu dreg (okara) and its utilization for high protein food products in IndonesiaRed oncom is an okara-based West Javanese food, supporting the distinction from peanut-cake black oncom.
Cited in: The microbiology of black oncom; Spore formation and colour; Why substrate composition matters; Bacterial contamination
BC Centre for Disease ControlSafety
Fermented Foods Safety Guidance: Section 1, Introduction to Fermented FoodsThe guide discusses starter identification and risks in fermented foods; it does not validate oncom.
Cited in: Recipe at a glance; Equipment; Method: documented black-oncom process; Stage 1 — Inspect the substrate; Stage 2 — Steam; Stage 3 — Form cakes; Stage 4 — Cool; Stage 5 — Inoculate; Stage 6 — Incubate; Stage 7 — Assess; How black oncom is eaten; Food safety: the peanut problem; Storage; Troubleshooting
OncomReference
Oncom: A Nutritive Functional Fermented Food Made from Food Process Solid Residue — Applied Sciences, 2024Cited by the written account of this record.
Cited in: Recipe at a glance; Equipment; Method: documented black-oncom process; Stage 1 — Inspect the substrate; Stage 2 — Steam; Stage 3 — Form cakes; Stage 4 — Cool; Stage 5 — Inoculate; Stage 6 — Incubate; Stage 7 — Assess; The microbiology of black oncom; Spore formation and colour; Why substrate composition matters; How black oncom is eaten; Bacterial contamination; Storage
Black-Oncom Production Photo Story, Cimanggu 2, BogorReference
Black-Oncom Production Photo Story, Cimanggu 2, Bogor — Polimedia, 2025Cited by the written account of this record.
Cited in: Recipe at a glance; Equipment; Method: documented black-oncom process; Stage 1 — Inspect the substrate; Stage 2 — Steam; Stage 3 — Form cakes; Stage 4 — Cool; Stage 5 — Inoculate; Stage 6 — Incubate; Stage 7 — Assess; The microbiology of black oncom; Spore formation and colour; Why substrate composition matters; How black oncom is eaten; Food safety: the peanut problem; Bacterial contamination; Storage; Troubleshooting
pmc.ncbi.nlm.nih.govReference
Neurospora intermedia from a Traditional Fermented Food Enables Waste-to-Food Conversion — Nature Microbiology, 2024Cited by the written account of this record.
Cited in: The microbiology of black oncom; Spore formation and colour; Why substrate composition matters; Bacterial contamination