# _Oncom_: A Nutritive Functional Fermented Food Made from Food Process Solid Residue
## 2 What Is \"Oncom\"? _Oncom_ is a native Indonesian fermented food made from various agricultural byproducts [4]. _Oncom_, which is primarily consumed in West Java, is used in various dishes such as _pepes oncom_, seaweed _oncom_, fried _oncom_, _sambal oncom_, or snacks such as _oncom_ chips, or used as an ingredient in several other cuisines such as added into _asinan_, laksa, _taoge goreng_ sauce, and as a filler for _combro_. Crispy fried _oncom_ is the most well-known snack product in the Bandung area under the name of _oncom_ chips and is available in various snack shops throughout West Java [26]. _Oncom_ is typically divided into red _oncom_ (Figure 1A) and black _oncom_ (Figure 1B) based on the different raw materials and moulds. Red _oncom_ is produced using _Neurospora_ sp., namely _N. crasa_, _N. intermedia_ var. _oncomensis_, and _N. sitophila_. Black _oncom_ is produced using _Rhizopus oligosporus_ and various varieties of _Mucor_ sp. [3; 21; 27]. Red _oncom_ is the fermented product of tofu dreg (_okana_) or peanut press cake with a thick layer of living conidia. The colour of red _oncom_ might be due to the conidia of the microorganisms that give a brilliant orange hue [3; 27]. The economic value of this product increases due to its conidial layer thickness. _Oncom_ is known as the only human food created by _Neurospora_ sp. In contrast to the pink and microscopic macroconidia of the natural _N. intermedia_, _N. intermedia_ var. _oncomensis_ has vivid yellow macroconidia [21]. The research by [PERSON] et al. [3] highlighted the role of ready-to-cook _oncom_ in the fermentation process. The types of inoculum growth in _oncom_ significantly influence its chemical characteristics (Table 1). For instance, _oncom_ fermented by pure _Neurospora_ sp. shows no significant difference in water content, but the total nitrogen content increases slightly, along with its soluble nitrogen content. Similarly, _Mucor_ sp. leads to a slight decrease in the total nitrogen content of Bandung red _oncom_, but an increase in the soluble nitrogen and reducing sugar content. _Rhizopus_ sp., on the other hand, increases the reducing sugar and soluble nitrogen content of the product. _Rhizopus_ sp. produced more soluble nitrogen compared to other two fungi types, especially _R. oligosporus_, which has been reported to have the ability to degrade protein. Soluble nitrogen and reducing sugars were said to contribute to taste, especially in _oncom_ fermented by _Rhizopus_ sp. [3]. It is important to note that _oncom_ is typically made using ready-to-cook _oncom_ from the previous day, a traditional practice that remains relevant in modern research. As mentioned previously, the raw materials of _oncom_ are mainly the waste of agricultural products, such as peanut press cake, tapioca solid waste, and tofu dreg (_okara_). The community mostly uses these raw materials as livestock additives or throws them away [26]. This is a pity since the materials still contain a high amount of protein, suitable as a nutrient source [3]. Black _oncom_ is usually made from peanut press cake mixed with tapioca solid waste. In contrast, the materials used to make red _oncom_ vary among regions; for instance, in Subang West Java, the producers use all three materials and wheat flour to make the red _oncom_, while in Bandung, only peanut press cake and tapioca solid waste are used [21]. Most traditional food fermentations in Indonesia are carried out naturally or spontaneously. This process, which relies on a variety of advantageous microorganisms from common ingredients and the environment, is a key element of the cultural heritage and authenticity of the product. These fermentations are often prepared on a small scale at home using old techniques that have been passed down from generation to generation. The use of natural fermentation and the lack of sterility mean that pure and single cultures are not engaged, and natural contamination and unstandardized product quality may result [21].