Changes of isoflavone in soybean cotyledons soaked in different volumes of water

Soybean cotyledons, recently dehulled, were soaked at 50 °C for 12 h as a pre treatment to obtain defatted soy flour enriched in aglycones. Grains of cultivar BRS 213 from the crop years 2004 and 2005 were used and initially had 1.4 and 1.2 mg g−1 of total isoflavones, respectively. The molar mass of malonyl and β-glycosides decreased after soaking (33% and 56.5%, in grains from the crop years 2004 and 2005, respectively), while the aglycones daidzein and genistein, that were previously undetectable, increased to 0.5 and 0.8 μmol g−1 in grains from the crop years 2004 and 2005, respectively. Cotyledons treated with the reduced volume of water had a reduction of 4% of the total isoflavone molar mass while, for the cotyledons treated with higher volume of water, there was a reduction of 14%, due to the leaching of isoflavones to the soaking water.