Soy protein isolate (SPI) fractions were produced by isoelectric precipitat
ion based on results of isoelectric focusing carried out on the crude soy e
xtract. The fractions were produced from crude protein extract (pH 9.0) seq
uentially and non-sequentially at isoelectric points (pIs) of 5.6, 5.1 and
4.5. Emulsions stabilised by soy proteins with pIs between 5.6 and 5.1 had
the highest (P <0.01) emulsion stability index (ESI), while those stabilise
d with proteins having pIs between 5.1 and 4.5 resulted in the lowest ESI f
or sequentially precipitated fractions. Non-sequential fractionation at pI
5.1 produced fractions with higher emulsifying activity index (EAI) than se
quential fractionation. SDS-PAGE profiles indicated that the fractions exhi
biting high functionality in terms of ESI and EAI were also richer in 7S gl
obulin protein subunits. (C) 2001 Society of Chemical Industry.