Pectin stabilization of soy protein isolates at low pH

The stabilizing behaviour of pectins in acidified dispersions of soy protein was studied. Objective of this work was to understand if different soy isolates and different pectins show differences in stability. The behaviour of a commercially available isolated soy protein (ISP) was compared to that of a soy protein in the laboratory. At pH 3.8 while suspensions of commercial ISP showed significant precipitation, the native SPI (prepared in the laboratory) was much more stable against precipitation. High methoxyl pectin (HMP) had better stabilization behaviour than low methoxyl pectin (LMP). A higher amount of HMP was needed to avoid protein precipitation of native SPI, compared to that used for commercial ISP. It was demonstrated that at low pH pectin forms soluble complexes with SPI through electrostatic interactions.