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Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: Pectin was de-esterified by U-PME or B-PME, pectinesterases that differed in cationic character and peptide composition. Pectin fractions of unmodified (O-Pec) and Valencia PME modified pectins (B-Pec and U-Pec) were separated by ion exchange (IEX) chromatography and characterized for calcium sensitivity by ζ-potential, texture profile analysis (TPA), and viscoelastic properties. U- and B-Pec had more negative ζ-potential than O-Pec, and became increasingly negative at higher pH values. Without CaCl2, viscosity of O-Pec was higher than B- and U-Pec. With 35mM CaCl2, B- and U-Pec gelled, but O-Pec did not gel. TPA values were not significantly different between B-Pec and U-Pec. The G'' values of O-Pec was 20–50-fold lower than G'' for B-Pec or U-Pec. After separation with ion exchange chromatography, later eluting fractions formed stronger gels than earlier eluting fractions. However, pectin fractions had lower viscosity and G'' values than unfractionated pectin, which is likely related to molecular weight differences. Results show that U-Pec forms stronger gels than B-Pec that is related to length of charge block and numbers of de-esterified pectin molecules. [Copyright &y& Elsevier]

Abstract: The molecular weight (MW) distribution of whey proteins (WP) mixed with various pectins was investigated using size exclusion chromatography (HPSEC) combined with multi-angle laser light scattering (MALLS). Samples were prepared with 1, 2, 5, 8% WP and 1% pectin. Mixtures were studied at pH 6.0 and CaCl2 concentrations of 0, 5, 10mM. Aggregate formation was determined after heating at various temperatures. The interactions between WP and low methoxyl pectin were observed before heat treatment. In the absence of calcium, mixing pectins with WP increased the average molecular weight of the aggregates, but the degree of methoxylation of pectins did not affect the MW distribution of the aggregates. On the other hand, in the presence of calcium, low and high methoxyl pectins generated different molecular weight distributions. In addition, the presence of low methoxyl pectin seemed to have a protective effect on WP, as the aggregates showed a smaller molecular weight and a smaller peak. [Copyright &y& Elsevier]