Journal of the Science of Food and Agriculture
Soy protein isolate (SPI) fractions were produced using two different pore size micro®ltra-
tion membranes. Micro®ltration was carried out on SPI produced by isoelectric precipitation of a
crude protein extract. Five fractions were obtained: two retentates and two permeates from the two
membranes plus an intermediate fraction obtained as the retentate on the small-pore-size membrane
using the permeate from the larger-pore-size membrane. Emulsions stabilised by the retentate
fractions exhibited higher values (P < 0.01) of emulsion stability index (ESI) and emulsifying activity
index (EAI) than those stabilised with fractions made from the permeates. The intermediate fraction
gave intermediate ESI values, while the EAI values were not signi®cantly different from those for SPI
and one of the retentates. SDS-PAGE pro®les indicated that the fractions exhibiting high functionality
in terms of ESI and EAI were also richer in 7S globulin soy protein subunits