Brassicaceae oilseeds provide feedstocks for the biofuels industry, but value-added coproducts are necessary to supply financial incentives for increased production. Our objective was to use high-intensity ultrasound to optimize extraction of antioxidants from mustard (Brassica juncea) seed meal. The ultrasound-assisted extraction (UAE) variables included temperature, solvent-to-material ratio, sonication duration, and EtOH concentration. Extracts were analyzed for total phenolics content (TPC), antioxidant activity, and sinapine content. Conventional extraction using water and 70% EtOH (v/v) at 80 °C for 3×30 min yielded 7.83 ± 0.07 and 8.81 ± 0.17 mg sinapic acid equivalents (SAE)/g meal, respectively. UAE extraction at 40 °C for 30 min yielded similar phenolics content (8.85 ± 0.33 mg SAE/g meal) as conventional hot ethanolic extraction, but required less time and lower temperature. The highest TPC (13.79 ± 0.38 mg SAE/g meal) was in the 7-d aqueous extracts. Sonicated solutions of pure sinapine and sinapic acid showed 1st-order reaction kinetics with greater degradation of isolated compounds than those present in extracts. Sinapine contained in extracts showed insignificant (P < 0.05) degradation after 30 min of sonication. Our research indicates that ultrasound treatment can assist the extraction of antioxidants from B. juncea meal by reducing both the temperature and time requirement without significant degradation of the primary antioxidants present.
Brassicaceae seed meals contain residual compounds with antioxidant and antimicrobial properties that may be incorporated in various food products to extend their shelf life. Ultrasound-assisted extraction can potentially enhance the extraction of these compounds for the development of value-added products.