CONICET | Buscador de Institutos y Recursos Humanos

The effects of several modifications to soybean protein isolate (SPI) production on genistein seriescomposition and content were analyzed. Combined variations of protein extraction pH and proteinprecipitation pH revealed that the maximum content of total genistein series was obtained with proteinextraction at pH 8.0 and protein precipitation at pH 3.5. When protein extraction was carried out at pH11.0, the saponification of malonylgenistin, resulting in genistin production, led to a decrease in isoflavonecontent. This fact was attributed to the low affinity of genistin for b-conglycinin. Malonylgenistinexhibited a high level of association with both glycinin and b-conglycinin at precipitation conditions.When temperature was reduced from 20 to 0 C during protein precipitation, the genistein series contentincreased if the b-glucosidase activity was inhibited. This increase was at the expense of glucosilatedforms. The nature of the interaction between soybean proteins and malonylgenistein and genistinseemed to be e at least in part e enthalpic in nature. In particular, malonylgenistin at pH 3.5 establishesanother kind of interaction with protein, besides enthalpic ones. Glycinin exhibited higher affinities forgenistein series components than b-conglycinin, the interactions being more stable at acidic than atalkaline pHs.