Taste characterization of okara and okara-derived substrates fermented by Pleurotus ostreatus mycelium

Given its degradative capacity, mycelium may valorize okara, an underutilized agro-industrial by-product. This study aimed to conduct solid-state fermentation of okara and mixtures (okara with sawdust or wheat bran) using Pleurotus ostreatus mycelium and explore the potential of fermented okara as an alternative food, focusing on its taste characteristics. The fastest mycelial growth with dense cultures was achieved on non-dried okara, followed by wheat bran (11-12 days). Fermentation enhanced the nitrogen content in okara, indicating an improved protein level. Following biotransformation, substrates obtained higher concentrations of glucose (2.78- to 6.39-fold rise), free amino acids (2.16- to 6.58-fold rise), and 5'-nucleotides (3.24- to 6.31-fold rise), with succinic acid being the predominant organic acid. Electronic tongue measurement revealed reduced sourness and enhanced umami taste and richness of okara. This work demonstrated the potential of P. ostreatus for the bioconversion of okara and mixed media to acquire products with a palatable taste.