Abstract:

The objective of this work was to assay the effect of solid-state fermentation (SSF) on the major nutritional
components and antioxidant activity of okara with the aim to obtain value-added fermented okara and to develop it into
functional foods. Individual cultures of Rhizopus oryzae or Rhizopus oligosporus were used to ferment okara in solid-state
cultivation and changes in reducing sugar, soluble protein, cellulase activity, glycoamylase activity, and protease activity
were expored during the fermentation. In addition, reducing power, 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)
diammonium salt (ABTS) scavenging capacity and ferrous ion chelating activity assays were carried out to investigate
the antioxidant activities of fermented okara. Results showed that reducing sugar, soluble protein, cellulase activity,
glycoamylase activity and protease activity increased significantly as fermentation progressed. Fermented okara showed
high antioxidant activities in terms of reducing power, ABTS+· scavenging capacity and ferrous ion-chelating activity.
Compared with the unfermented control, these antioxidant activities increased by 1.63, 1.48 and 2.82 folds for okara
fermented by Rhizopus oryzae for 24 h, and by 1.88, 1.63 and 3.18 folds for okara fermented by Rhizopus oligosporus for
24 h, respectively. Thus, the present study showed that fermented okara with enhanced nutritional properties and antioxidant
capacity can be served as nutraceuticals and functional foods for health promotion.

Key words: okara, solid-state fermentation, nutritional components, antioxidant activities