Abstract:Stress relaxation is the result of timedependent decay of intermolecular forces under a constant imposed strain. A stress relaxation experiment is one of the most important evaluation tools to study the viscoelastic properties of materials and it reflects indirectly the microstructure changes without disrupting them during the processing. Aiming to investigate the gelation properties of low acyl (LA) and high acyl (HA) mixed acid gellan gum gels (L/HGLG) using stress relaxation parameters. Influences of LA/HA weight ratio, gellan concentration and pH value on the gelation properties of L/HGLG were studied. The results showed that the stress relaxation behavior of L/HGLG fitted well with Pelegs empirical model. Meanwhile, LA/HA weight ratio, pH value and gellan concentration had a pronounced effect on the stress relaxation behavior of mixed acid gellan gum gels. The values of equilibrium modulus (EA) correlated well with gel hardness, indicating that EA could represent the gel strength. EA and k1 were increased firstly and then decreased with the increase of LA/HA weight ratio, reaching a maximum at around 50% high acyl gellan variant. This suggested that the biopolymers were now forming an interpenetrating network structure. The higher the gellan concentration was, the larger the EA was. In addition, high acyl gellan was less sensitive to changes in pH values, and subsequently no evidence of acid gelation was observed with high acyl gellan at higher proportion. The findings demonstrated that structuring as well as destructuring of mixed gellan acid gels can be controlled in acidic environments similar to those that were presented in the stomach after food consumption.