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Soybean is an important Brazilian agricultural commodity that contains a high concentration of isoflavones. Many studies showed that isoflavones are active in the prevention of many human diseases. However, the correct processing techniques used to prepare the soy foodstuffs are important to maintain the active forms. The objective of this study was to evaluate the effect of gamma irradiation on the isoflavone contents of the defatted soybean flour when compared with soybean molasses, a derivative from the soybean food production. After extracting phenolic compounds with methanol aqueous solution (80%), isoflavones were detected by reverse-phase high-performance liquid chromatography/diode-array detector. The radiation doses of 2 and 5 kGy presented a small effect on the isoflavones content of defatted soy flour. Samples irradiated at 50 kGy showed lower isoflavone contents. The observed reduction in the concentration of isoflavones-daidzein, glycitein and genistein-induced by gamma radiation in soy molasses was not significant in defatted soy flour, thus suggesting that isoflavones in defatted soy flour were not eliminated by gamma radiation at rates up to 50 kGy.

Traditionally, food is associated with energetic and nutritious characteristics such as sources of carbohydrates, proteins and lipids. Recently, however, foods with bioactive substances such as isoflavones have received great attention. The objective of this study was therefore to evaluate the presence of the isoflavones daidzein, glycitein, genistein and their conjugated forms in grains and leaves of several leguminous plants utilized largely in Brazilian cuisine. Grains used in Peruvian cuisine were also analyzed. After extracting phenolic compounds with methanol (80%), isoflavones as detected by reversed-phase high-performance liquid chromatography/ diode-array detector were only found in chickpeas and soybean. Chickpea extracts showed only the isoflavone genistein at 31 microg/g defatted flour. Detection of these isoflavones was confirmed by electrospray ionization mass and tandem mass spectrometric experiments. For soybean, a distinct distribution of isoflavones was found in hypocotyls and cotyledon. The highest concentration of isoflavones found was approximately 5.9 mg/g for hypocotyls, whereas the total concentration of isoflavone was around 0.4 mg/g for the cotyledons (dry matter). These results indicate that isoflavone concentrations vary within the different tissues of the leguminous species tested.