Effects of genotypes, environments and hydrothermal treatments on the isoflavone aglycone concentration in soybean grains

The objective of this work was to assess the effects of hydrothermal treatments and the environmental and genetic variability on the isoflavone aglycones concentration in soybean [Glycine max (L.) Merrill] grains. The study was carried out with the soybean cultivars BR 36, FEPAGRO RS-10, and BRS 155, cultivated in three locals of Parana State (Londrina, Capanema, and Palmas), during 1999/2000 soybean season, submitted to hydrothermal treatments at 40, 50 and 60degreesC for 12 and 18 hours. Higher concentrations of total isoflavones (280 mg/100 g) were observed in grains harvested in Palmas, where the average temperature during pod filling was 19degreesC. In Londrina (23degreesC), there was lower concentration of isoflavones (140 mg/100 g). The cultivar BRS 155 presented the highest content of total isoflavones in Palmas and in Londrina. Non-treated grains of BRS 155 showed in average 4.0 mg/100 g of aglycones, which increased to 52 mg/100 g, after hydrothermal treatments. The treatment at 50degreesC for 12 hours was the most effective in developing isoflavone aglycones. At 60degreesC, there was a decrease of the aglycones, due to inactivation of beta-glycosidases. Malonyl forms, which are thermal unstable, were reduced at higher temperatures.