Effect of extraction conditions on the composition of
soy protein isolates
Table 3 shows the effects of the protein extraction conditions on
the chemical composition of the resulting isolates. The “Standard
Method” SPI had the highest protein content followed by “Acid
Pre-Treatment” and “Heat Precipitation” SPIs. The samples that
were resolubilized at pH 5 and 6 exhibited lower protein
(u:P < 0.001) and ash content (P < 0.001). It is unclear why the protein
contents of these samples decreased. The lower ash content
could be explained by the smaller amount of salt formed during the
adjustment of the protein dispersion to these pHs compared with
neutral pH 7.0. The acid pretreated SPI had the fluffiest texture
and the lightest color among other SPIs (visual observation), probably
due to the fact that most pigments and carbohydrates were
removed with the supernatant after the 1st centrifugation.