# _Oncom_: A Nutritive Functional Fermented Food Made from Food Process Solid Residue
## 3 From Waste to a Nutritious Food
### Oncom and Nutrient Digestibility  
Soybeans, as the raw material of _oncom_, are known to contain antimutrient factors such as phytic acid, trypsin inhibitors, lectin, and soybean oligosaccharides (SBOSs) [29; 61], which reduce the digestibility of nutrient and mineral absorption [62]. Soybean oligosaccharides (SBOSs) are soluble oligosaccharides in soy or other legumes [63; 64]. SBOSs consist mainly of raffinose, stachyose, and sucrose [64]. Raffinose and stachyose are the major bioactive components of SBOSs [63; 65], used in fermentation in soybean fermented products such as _oncom_, tempeh, and soy sauce [9].  
_Oncom_ is a source of potential nutrition for society, since during fermentation, complex chemical components will break down into simpler chemicals that are easier for the body to digest and utilize [56; 66; 67]. Raffinose and stachyose may be hydrolysed during fermentation, thus contributing to increased digestibility. It was found that within the first 21 h of fermentation, _N. sitophila_, the mould most frequently employed to ferment peanut press cake in making _oncom_, almost eliminated sucrose and the intestinal gas-forming sugars raffinose and stachyose. The enhanced digestibility of _oncom_ that has been suggested may be caused by _N. sitophila_ utilizing carbohydrates that cause flatulence [68]. Because of the fermenting process, it has a higher protein digestibility (89.9%) than peanuts [69].  
Antinutrients are reduced or inactivated by soaking, boiling, and fermentation methods, mainly controlled fermentation [29; 62]. During fermentation, lactic acid bacteria (LAB)-mediated fermentation reduces phytates, trypsin inhibitors, and lectins [70]. _R. oligosaccharides_ has vigorous phytase activity to reduce phytic acid content during the _oncom_ fermentation process for 72 h of _oncom_ fermentation [19]. [PERSON] et al. [71] reported that fermentation with _A. oryzae_ and _N. intermedia_ increased protein digestibility by 24-47% depending on the optimum length of the fermentation period and the type of mould (_N. sitophila_ and _R. oligosaccharides_). The moulds produce proteolytic enzymes that can hydrolyse proteins of raw products into peptides and free amino acids during fermentation [23]. Free amino released from the amino acids can then bind to antimutrients [46]. In addition, the moulds can produce the invertase enzyme, which can break down sucrose into fructose and glucose, and also produce the enzyme alpha-galactosidase, which can break down raffinose and stachyose into galactose and sucrose [56], which can then enhance nutrient and mineral digestibility and bioavailability [62; 72]. However, the effect of these two fungi in degrading SBOSs still needs further investigation.  
The moulds involved in the _oncom_ manufacturing process produce lipase and protease enzymes to degrade the starch into sugar during fermentation [56]. [PERSON] et al. [73] reported that _R. oligosporus_ has been found to produce lipases in solid-state fermentation and has the highest productivity of lipases among other mould samples.