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Low Methoxyl pectin / sodium caseinate complexing behavior studied by isothermal titration calorimetry

Wang, Jian, Dumas, Emilie, Gharsallaoui, Adem
Food hydrocolloids 2019 v.88 pp. 163-169
biopolymers, calorimetry, electrostatic interactions, encapsulation, hydrocolloids, ionic strength, pH, pectins, separation, sodium caseinate, sodium chloride, temperature, titration, transmittance, zeta potential
The formation of Low Methoxyl pectin (LMP)/sodium caseinate (CAS) complexes was studied at different pHs by measuring transmittance, phase separation and ζ-potential. At the different tested CAS/LMP ratios, insoluble complexes, soluble complexes and biopolymer solutions were formed at pH 3.0, 5.0 and 7.0, respectively. In order to study the interactions between CAS and LMP in these three different conditions, isothermal titration calorimetry (ITC) was used. The results showed that there were no significant interactions at pH 7.0 while electrostatic interactions were predominant in both soluble and insoluble complexes. The electrostatic interactions in insoluble complexes were much stronger than in soluble complexes. The effect of ionic strength and temperature on the formation of insoluble complexes at pH 3.0 was also studied by ITC. The presence of sodium chloride was shown to inhibit the electrostatic interactions until a threshold CAS/LMP ratio, and high temperature favored the attractive interactions between CAS and LMP. The data obtained in this study should allow efficient development of encapsulation systems by complex coacervation.