Value-adding Okara via Monascus purpureus solid-state fermentation: Microstructural remodeling, metabolite...

Area of Science:

• Food Science and Technology
• Biotechnology
• Nutraceuticals

Background:

• Okara, a soybean processing by-product, is rich in bioactive compounds but underutilized due to sensory and digestibility issues.
• Current disposal methods for okara raise environmental concerns.
• Valorization of okara is crucial for sustainable food systems and resource efficiency.

Purpose of the Study:

• To upcycle okara into a valuable nutraceutical ingredient through solid-state fermentation with Monascus purpureus.
• To investigate the structural, chemical, and functional transformations of okara during fermentation.
• To develop a sustainable and citrinin-free process for okara upcycling.

Main Methods:

• Solid-state fermentation of okara using Monascus purpureus for 25 days.
• Scanning Electron Microscopy (SEM) for structural analysis.
• Ultra-Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS) and Gas Chromatography-Mass Spectrometry (GC-MS) for chemical profiling.
• Functional assays including antioxidant activity, α-glucosidase inhibition, and lipid accumulation studies in 3T3-L1 cells.

Main Results:

• Fermentation enhanced okara's porosity, water-holding, water-swelling, oil-absorption, and cholesterol-binding capacities.
• Significant increases in total phenolics (2.27-fold), flavonoids (3.08-fold), and saponins (1.70-fold) were observed.
• Accumulation of ergosterol (688.85 mg/kg), monacolin K (24.96 mg/kg), and L-carnitine (332.21 mg/kg) occurred, with no detectable citrinin.
• β-glucosidase activity converted isoflavone glycosides to bioactive aglycones, improving antioxidant and α-glucosidase inhibitory properties.
• Reduced lipid accumulation in 3T3-L1 cells indicated potential anti-obesity effects.

Conclusions:

• Solid-state fermentation with M. purpureus effectively upcycles okara, transforming its structure and enhancing its functional properties.
• The process yields a citrinin-free nutraceutical ingredient rich in bioactive compounds like monacolin K and ergosterol.
• Fermented okara demonstrates potential for use in functional foods and health supplements due to improved nutritional and bioactivity profiles.