Impact of oat pretreatment on okara composition and its upcycling using a filamentous fungus for food applications: A biorefinery approach

Oat milk production generates a substantial amount of a byproduct, named oat okara, which holds promise in advancing circular economy practices in the food industry when upcycled into food products or ingredients. In this study, filamentous fungus, Rhizopus oligosporus was employed to enhance nutritional properties, including a reduction of antinutritional factors. The fermented oat okara food product showed a modest increase in protein content, improvement in amino acid profiles, and reduction in phytic acid and saturated fatty acids relative to raw okara. In the second phase of the study, oat okara was produced through various enzymatic (α-amylase) and acidic (HCl, H₃PO₄) pretreatments to assess their impact on okara composition. The results demonstrated substantial starch reduction, especially under high enzyme load, and notable increase in protein and fiber contents. Overall, the results underscored that controlling processing parameters—particularly enzyme dosage and acid type—can significantly alter oat okara’s nutritional and functional properties, making it more suitable for incorporation into functional food products.