The effect of sodium hexametaphosphate on the efficiency of pectin in stabilizing acidified milk drinks

The combined effect of sodium hexametaphosphate (SHMP) (0.0125%, 0.025% and 0.05% w/w) and High methoxyl (HM)-pectin (0.06–0.42% w/w) on the stability and physico-chemical properties of acidified milk drinks (AMDs) was investigated. Analytical centrifugation, particle size distributions, zeta potential, steady shear, and oscillatory rheological measurements were used to characterize the AMD samples. Results indicated that the addition of 0.025% w/w was able to improve stability of the samples by a factor of 1.7 or more, depending on the pectin concentration. In the presence of SHMP, pectin-stabilized AMD samples had smaller particle size and polydispersity. Steady shear rheological data showed that the increase in viscosity due to bridging flocculation at the smallest pectin dosages was reduced by SHMP, whereas a synergistic effect was observed when SHMP was added to samples with a higher concentration of pectin. This study revealed that SHMP could numerically increase the zeta potential of AMD to more negative values. Thus higher stability was achieved by boosting the electrostatic interactions and the formation of soluble protein-pectin complexes. The presence of SHMP augmented the viscosity of the AMD samples with the highest pectin dosages, perhaps owing to an extended structure of pectin in the presence of less available calcium ions. Results of this study contribute to the general understanding of protein-polysaccharide interactions in acidified milk drinks and inspire to finding ways to improve the efficiency of stabilizers.