Pectin stabilization of isolated soy protein at acidified pH.

摘要

This thesis focuses on the stabilization behaviour of pectin in soy protein dispersions at pH 3.8. Mixed systems containing laboratory prepared SPI (native SPI) or commercial isolated soy protein (ISP) and high or low methoxyl pectin were studied at pH 3.8. While commercial ISP was not soluble at pH 3.8 and needed 0.1% pectin to form soluble complexes, native SPI was soluble at pH 3.8 in the absence of pectin. Both high and low methoxyl pectins formed complexes with soy protein, however high methoxyl pectin was found to be a better stabilizer. The size of native SPI and its fractions (11S and 7S) was determined using scanning electron microscopy and image analysis, after covalent immobilization of the protein on carbon planchets. The same technique was also used to determine if there were differences in the association behaviour of pectin with soy protein depending on the type of protein present in the isolate. It was concluded that pectin interacts with both major soy protein particles (7S and 11S) via electrostatic interactions, and the stabilization behaviour of the complexes varies depending on their composition.