Abstract:

The effect of cryopreservation conditions (SPI/water ratio, temperature and time) on the structure (sulfhydrylgroup, disulfide bond and surface hydrophobicity) of soybean protein isolate (SPI) was investigated. Results indicated thatthe contents of free sulfhydryl group and disulfide bond were decreased with reducing SPI/water ratio, and the content ofexposed sulfhydryl group and surface hydrophobicity were increased initially and then decreased. The contents of freesulfhydryl group and disulfide bond as well as surface hydrophobicity were reduced with lowered temperature and prolongedfreezing time. SPI was denatured to some extent after freezing and contained significantly higher contents of free sulfhydrylgroup at not too low temperature than the unfrozen one. Moreover, most intramolecular disulfide bonds were transformedinto intermolecular ones during the cryopreservation process.

Key words: cryopreservation, soy protein isolate, sulfhydryl group, surface hydrophobicity