Extracting and purifying isoflavones from defatted soybean flakes using superheated water at elevated pressures

This paper focusses mainly on improving superheated water extraction conditions using the simulation optimization approach known as “steepest ascent”. The study examines the effect of operating conditions on the amount of five isoflavones extracted from defatted soybean flakes (DSF) using superheated water extraction (SWE), stirred solvent extraction, Soxhlet methanol extraction, and pressurized water extraction (PWE). Amberlite XAD16-HP adsorbent was used to purify five isoflavones obtained by reverse phase solid extraction. HPLC analysis was conducted to quantify these five isoflavones as proportions of the amount of total isoflavones (TIF). The steepest ascent design for SWE revealed that the optimum condition was 110 °C and 641 psig (4520 kPa) over 2.3 h of extraction. Under these condition, 3937 TIF μg/g DSF was produced. Solid phase purification, by Amberlite XAD16-HP absorption, yielded a solid with 37.0 purity and 49.0 de-sorption recovery of total isoflavones.