Sustainable Valorization of Soybean Husk via Green Extraction Technologies: Bioactive Compound Recovery and Formulation of Fiber-Enriched Scones

Soybean husk (SH), a major processing by-product, is a rich source of fiber and antioxidants. This study characterized SH and optimized bioactive compound recovery using green technologies: ultrasound-assisted extraction (UAE) and pressurized liquid extraction (PLE). Raw SH contained high fiber (67.98%) and moderate protein (10.56%). Experimental designs evaluated temperature, power, and solvent composition (EtOH/H2O). In UAE, yield increased with longer time and 50% ethanol. However, PLE significantly outperformed UAE; optimal conditions (140 °C, 50% EtOH) yielded 19.97% extract, with 17.1 mg GAE/g total phenolics and 167.6 µmol TE/g antioxidant capacity. Isoflavone profiling identified daidzin, genistin, and their malonyl/acetyl derivatives as predominant. The optimal extract and raw SH were incorporated into scone formulations to evaluate functional potential. Results showed that scones containing extract (alone or with SH) exhibited significantly higher phenolic content and antioxidant activity (≈36 µmol Trolox/g) than controls. SH addition increased dietary fiber, qualifying the product as a “source of fiber” under current regulations. This research demonstrates that SH valorization through PLE enhances the nutritional and functional quality of bakery products.