Charge domain of modified pectins influence interaction with acidified caseins

The interaction of non-fat dry milk, caseinate and casein (CSN) fractions with charge modified pectins (B-Pec and U-Pec) and unmodified pectin (O-Pec) in acidified dispersion systems was investigated. U-Pec led to more precipitation of proteins than O-Pec or B-Pec. Casein dispersions with pectin had larger particle size, especially U-Pec and B-Pec, than dispersions without pectin. Dispersions with charge modified pectins showed more negative ζ-potential than dispersions with unmodified pectin or dispersions without pectin. U-Pec enhanced negative ζ-potential of β-CSN more than B-Pec. There was no significant difference in flow behavior among non-fat milk samples regardless of pectins added. In contrast, non-Newtonian behavior, shear thinning behavior was observed in modified pectin added κ-CSN. Analysis by light microscopy of non-fat milk and κ-CSN showed that sizes and shapes were changed by addition of O-Pec and U-Pec. The results suggest a specific affinity between pectin and κ-CSN, which is related to the charge distribution of pectin.