Regulation on gel textures of Nicandra physalodes (Linn.) Gaertn. pectin by its synergistic interaction with sodium alginate

Abstract

Synergism between different types of polysaccharides is important to imparting textural preferences and decreasing product costs. In this study, Nicandra physalodes (Linn.) Gaertn. pectin (NPGP) was found to synergistically interact with sodium alginate (SA) under an acidification process by glucono-δ-lactone (GDL) addition. This synergistic interaction led to the formation of much stronger NPGP/SA mixed gels than the pure NPGP and SA gels. During the acidification process, the pH values corresponding to the onset of the synergistic gelation slightly varied depending on NPGP to SA mixing ratios, but in all systems, the synergistic gelation was initiated at pH < 3.6, indicating that sufficient electrostatic suppression on NPGP and SA chains is required for the synergistic gelation. To this end, the addition of a small amount of Na + (0.1%, w/v ) slightly promoted the gelation process. Moreover, the optimum synergistic ratio in the mixed gels was unchanged irrespective of Na + addition, always located at NPGP:SA = 4:6. In order to reveal the network type, theoretical simulations including “iso-strain”, “iso-stress” and “additivity” models were further performed, which suggested that the network structure in mixed NPGP/SA gels is synergistic network rather than phase separated or interpenetrating networks. Further measurements on gel stability suggested that the synergistic NPGP/SA gels showed good freeze-thawing stability, while heating at 80 °C significantly decreased the gel strength, especially at high SA ratios. Overall, these results highlight the potential application of NPGP and SA mixtures in formulations of acidic gel foods. • NPGP can synergistically interact with sodium alginate (SA) under acidic media. • The optimum synergistic ratio between NPGP and SA is 4:6. • Addition of Na + did not change the optimum synergistic ratio. • The network type in the mixed gels was recognized as synergistic network.