Effect of interaction between sorbitol and gelatin on gelatin properties and its mechanism under different citric acid concentrations

In this study, the effects of citric acid (CA) concentrations on the gelatin/sorbitol gel properties and the interaction mechanisms were investigated. Furthermore, the alternative effect of sorbitol on sucrose was also investigated and compared in gelatin gel systems. The results showed that the gel strength, viscosity and gelling/melting temperatures of gelatin could be “protected” due to the sorbitol addition at a low CA concentration (<0.5%). As the CA concentration gradually increased, the values of these indicators in the gelatin/sorbitol group were close to those of the gelatin/sucrose group, showing no obvious difference. The SDS-PAGE results indicated that this “protective” effect of sorbitol on gelatin was mainly reflected in the reduction of polymer subunit components degradation of gelatin. The X-ray diffraction (XRD) results showed that the sorbitol addition promoted the triple helical structure formation of gelatin at a low CA concentration (<0.5%). However, the high CA concentration not only destroyed the hydrogen bonds formed by sorbitol, but also destroyed the structure of the gelatin. The increase in the yellowness value of the gel color and the peak shifts of the amide I and II bands probably implied the occurrence of the Maillard reactions between sucrose and gelatin, which is not found in gelatin/sorbitol group. Hence, sorbitol can be used as a good alternative to sucrose in gelatin sweet products.