Use of soybean residue (okara) as a substrate component for oyster mushrooms

Abstract

The applicability of soybean residue (okara) as a growing medium component for oyster mushroom cultivation was studied. Sawdust was used as the base media with a total of 30 % supplementation (mixture of okara and wheat bran; okara%: 0 %, 10 %, 15 %, 20 %, 30 %) or without supplements (control). Growing periods and mushroom quality varied depending on the medium compositions. Fresh weights of first flushes from supplemented media were about two-fold higher than the control. Supplementation using 20 % okara + 10 % wheat bran resulted in the maximum biological yield (199.58 g mushrooms/kg substrate) and bioefficiency (39.92 %). Substrates containing 10 %, 20 %, or 30 % okara provided mushrooms with higher protein contents (29.15–30.39 %). With supplementation, ash levels expanded from 5.90 to 9.79 %, but fat levels were not much affected. Supplementation enhanced the total phenolic content of mushrooms from 272.59 mg/100 g to 374.01 mg/100 g. 30 % wheat bran-added media contributed to the highest DPPH radical scavenging activity (226.70 mg/100 g). Based on electronic tongue measurement, 30 % okara supplementation elevated the mushroom umami taste from 11.71 to 12.02. Higher richness (9.84–9.91) was associated with either 30 % wheat bran or 20 % okara supplementation levels. Overall, this study demonstrated the potential of okara as a low or no-cost supplement to increase oyster mushroom yields. This work suggested an approach to substitute or reduce the usage of a commercial supplement (wheat bran), which may be costly or not locally available. Furthermore, this study revealed several desirable nutritional, antioxidant, and taste attributes in mushrooms that can be improved via okara or mixed supplementations.