Inoculation fermentation improves the nutritional quality and flavor profile of Chinese traditional fermented okara (Meitauza): a comparison with a commercial benchmark.

INTRODUCTION

This study compared the effects of inoculated fermentation with pure Mucor racemosus (MMtz), Bacillus subtilis (BMtz), or Actinomucor elegans (AMtz) strains or a mixed culture of M. racemosus and B. subtilis (MBMtz) on the transformation of soybean residue (okara) into Meitauza relative to a commercially sourced traditional Meitauza (TMtz) used as an industry benchmark.

METHODS

Inoculated fermentation markedly improved nutritional quality. The BMtz sampled exhibited the highest soluble protein (31.25 g/kg) and free amino acid contents (141.00 g/kg). The MBMtz samples exhibited synergistically increased reducing sugar levels (38.20 g/kg) and the highest antioxidant capacity with a 57% hydroxyl radical scavenging rate and stable iron-reducing power. Gas chromatography-mass spectrometry analysis identified 242 volatile compounds that contributed to differential flavors.

RESULTS

The MBMtz samples exhibited the most complex and desirable aroma, which was characterized by fruity esters (12.77%) and fresh alcohols (14.86%). The pyrazines were abundant in BMtz samples (23.00%), conferring roasted and nutty aromas. A. elegans maintained a slightly alkaline environment and contributed unique volatiles, while M. racemosus was an effective single inoculum.

DISCUSSION: These findings indicate that targeted inoculation is a useful strategy to standardize and optimize Meitauza production, promoting soybean processing waste into a nutritionally enhanced, flavor-rich, and functional food product.