Interaction and Stabilization of Acidified Casein Dispersions with Low and High Methoxyl Pectins

The ability of low (LMP) and high methoxyl pectins (HMP) to stabilize acidified sodium caseinate dispersions was evaluated. Samples of 2.5% casein, 1% pectin, and 2.5% casein−1% pectin were hydrated in a 0.1 constant ionic strength buffer and pH was adjusted to 3.8, 4.8, 5.8, and 6.8. Without pectin, casein precipitated at pH 3.8 and 4.8. In single-component dispersions, pH had little influence on turbidity, L values, sedimentation, and apparent viscosity. L values for dispersions of LMP−casein and HMP−casein at pH 3.8 and 4.8 were about twice those at pH 5.8 and 6.8 and were higher than those for pectin. Apparent viscosity of LMP−casein and HMP−casein dispersions was not influenced by pH as were turbidity and L values. At low pH, dispersions were less Newtonian and had greater consistency index. Increased stability and apparent viscosity were consistent with fewer interactive sites between HMP and casein than between LMP and casein.