Synergistic gelling mechanism of RG-I rich citrus pectic polysaccharide at different esterification degree in calcium-induced gelation.

RG-I rich pectic polysaccharide is common in fruit and vegetable and possesses health benefits. However, it is removed during commercial pectin production because of poor gelling properties. Synergistic gelation can improve rheological properties of RG-I pectic polysaccharide and expand its application in functional food hydrocolloids. In the study, RG-I rich pectic polysaccharides at different degree of esterification was extracted from citrus membrane by sequential mild acidic (0.4% HCl, 28 °C) and alkaline (0.6% NaOH, 32 °C) treatment. The pectic polysaccharide from acid water (PA) composes of 41% RG-I and 44% HG with DM of 45%, while the pectic polysaccharide from basic water (PB) composed of 63% RG-I and 19% HG with DM of 15%. PA/PB blend gel under CaCO3-glucono-δ-lactone system showed improved rheological properties compared with pure gels. Ca-bridges connected pectin aggregates and promoted the three-dimensional structure of PA/PB blend gels, while neutral sugar side-chains prompted hydrogen bonds and strengthened gel network.