The influence of high pressure (HP) treatment (200-600 MPa) on the emulsify
ing activity index (EAI) and emulsifying stability index (ESI) on the 7S an
d 11S globulins and soya protein isolate (SPI) at pHs 7.5 and 6.5, at diffe
rent concentrations (0.25-0.75%) was studied. Solubility and surface hydrop
hobicity were used as indices of the degree of denaturation caused by HP. 7
S showed the highest EAI and surface hydrophobicity after treatment at 400
MPa, whereas 11S showed its highest EAI and surface hydrophobicity after tr
eatment at 200 MPa. No significant correlation (P > 0.05) was found between
solubility and EAI or hydrophobicity. SPI showed the optimum value of EAI
after treatment at 400 MPa although its surface hydrophobicity was low. It
is suggested that pressure at 400 MPa dissociated the 7S of the SPI into pa
rtially or totally denatured monomers that enhanced the surface activity bu
t at the same time, the unfolding of the polypeptides of the 11S within the
hexamer led to aggregation, negatively affecting the surface hydrophobicit
y of the: SPI. The ESI values for the nontreated samples of SPI, 7S and 11S
were higher at lower concentrations. At the same pH and concentration, the
ESI decreased with increasing tip, except for the 7S at pH 7.5 and a prote
in concentration of 0.75%. (C) 2001 Elsevier Science Ltd. All rights reserv
ed.