The purpose of this study was to determine the effect of ultrasound treatment on the contents of daidzin, genistin, and their respective aglycones, daidzein and genistein, in resultant soymilk. Soybean slurry was exposed to ultrasound treatment, filtered, and placed in an ultrasound cleaning bath set with different frequencies (35and 130 KHz), treatment temperatures (20 and 40 °C), and times (20, 40, and 60 min). Concentrations for these isoflavones were determined using reverse-phase high-performance liquid chromatography. Results indicated that both frequencies significantly (p < 0.05) increased isoflavone content (IC), glycosides, and aglycones in extracted soymilk. These results were attributed to induced cavitation, which increases the permeability of plant tissues. However, the frequency of 35 kHz caused a noticeably higher increase in IC than 130 kHz. Results also revealed significant increases in IC with increased sonication time (from 20 to 60 min) and with increased temperature (from 20 to 40 °C).
Keywords: Daidzein; Daidzin; Genistein; Genistin; Isoflavones; Soymilk; Ultrasound.