Characterization of gellan gum-chitosan based hydrogel to evaluate as a potential gelatin substitute

Although low-acyl gellan forms a hard and brittle gel, it can be used to replace of gelatin if it is modified according to the required properties of the end product. In this study, the effect of the chitosan on the mechanical, rheological, and structural properties of low acyl gellan gum (GG) hydrogel was investigated. Polyelectrolyte complex interaction of low acyl gellan gum and chitosan (GG/CS) was induced by the addition of salt (potassium citrate) and citric acid. All concentrations were optimized using the central composite design to approach the gel hardness and springiness to those values of high bloom gelatin. The interaction of gellan and chitosan was confirmed by Fourier transform-infra-red spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The TPA results showed that chitosan could increase the springiness of GG hydrogel from 0.705 ± 0.04 to 0.848 ± 0.02 and decrease the hardness from 2849.32 ± 101.90 to 1061.36 ± 20.15 (p < 0.05). In addition, the syneresis of GG hydrogel (1.92%) was decreased to 1.56% in GG/CS hydrogel. Furthermore, the results of zeta potential measurements showed an increase of the value from −24.33 ± 0.45 to −5.1 ± 0.65 for GG and GG/CS hydrogels, respectively. The results revealed that in this method, chitosan could establish electrostatic interaction with gellan gum, which makes it a proper replacer for high bloom gelatin.