Green extraction of antioxidants from Brewer's spent grain using Ohmic-accelerated steam distillation with NaCl electrolytes

This study proposed an Ohmic-Accelerated Steam Distillation (OASD) process and systematically evaluated the effects of electric-field strength (0-40 V/cm) and NaCl concentration (0-0.10 M). The key findings demonstrate that the combined electric field and ionic enhancement significantly accelerated mass transfer and markedly improved the recovery of major bioactive compounds. An optimal synergy was found at 15 V/cm with 0.01 M NaCl, which yielded extraction efficiencies of 41% for antioxidants and 30% for phenolics while substantially reducing extraction time from > 5.5h (without electric field and/or NaCl) to 50-60 min. Scanning electron microscopy and confocal laser scanning microscopy revealed increased cell-wall permeability with moderate structural disruption, consistent with enhanced mass transfer. Under these conditions, HPLC quantified recoveries of key bioactives-caffeic acid 48%, ferulic acid 69%, vanillic acid 67%, and tannins 75%. CLSM fluorescence analysis revealed a significant decrease in antioxidant-related regions (from 7899 to 1252 px²), further confirming enhanced extraction efficiency. Compared to conventional thermal extraction approaches, the optimized OASD method significantly improved bioactive recovery while preserving cellular integrity and reducing thermal degradation. This approach offers strong potential for applications in functional foods and health-related products, contributing to by-product valorization and the advancement of the circular economy in the food industry.