Supercritical fluid extraction of isoflavones from soybean flour

This study evaluated the use of supercritical carbon dioxide (SC-CO2) for the extraction of soybeans isoflavones (genistin, genistein and daidzein), where different temperatures, pressures and modifier percentages were tested and compared with conventional extraction methods (soxhlet and ultra-sonification) conducted in parallel. The extraction conditions were 40–70 °C, 200–360 bar, adding 0, 5 and 10 mol% of methanol 70% in water (v/v−1) as modifier. The HPLC analysis of the obtained extracts revealed that extraction of genistin and genistein at 70 °C/200 bar using a mixture of carbon dioxide (55.2 g) and modifier (10 mol%), resulted in lower values than conventional methods. The analytical results additionally showed a predominant effect of temperature in the amount of genistin and genistein extracted by SC-CO2. Extraction of daidzein at 50 °C/360 bar resulted in higher values than conventional methods and a predominant effect of the pressure was observed. A strong interaction between temperature and pressure was observed in the extraction of the tested isoflavones. The maximum amount of total isoflavonoids extracted by each method were: ultra-sonification (311.55 μg·g−1), soxhlet (212.86 μg·g−1) and SC-CO2 (86.28 μg·g−1).