The effects of xanthan and KCl on the subunit composition of soy proteins as well as on the formation of high molecular weight aggregates were evaluated from the electrophoretic patterns of the soluble proteins in the different buffers. Fig. 6 shows the electrophoretic patterns using non-reducing conditions for the DW and BU extracts. The results for the B extract were similar to those of the BU (not shown) one. The different components present in the SPI powder were identified by comparison with molecular weight markers and with standards found in the literature (Petruccelli & Añón, 1995c). The bands found in the SPI powder under non-reducing conditions were: α and α′ subunits of β-conglycinin (α− and α′-7S); β subunit of β-conglycinin (β−7S); acidic polypeptides of glycinin (A-11S) and basic polypeptides of glycinin (B-11S) and the AB subunit of glycinin (AB-11S). Low molecular weight peptides (**) and four bands of large soluble aggregates (*) with molecular weights above 115.5 kDa were also observed ( Fig. 6). The α and α′ subunits of the β-conglycinin probably formed the aggregates present in the two first bands (greater intensity). The other two bands contained the latter subunits plus the A polypeptide of 11S ( Petruccelli & Añón, 1995c).