低酰基/高酰基复合酸性结冷胶凝胶的凝胶特性研究

利用应力松弛模式研究了低酰基结冷胶(LA)/高酰基结冷胶(HA)质量配比、基体总浓度、pH值对低酰基/高酰基复合酸性结冷胶凝胶(L/H-GLG)凝胶特性的影响。结果表明,复合酸性凝胶的应力松弛行为可用Peleg模型进行拟合,平衡模量EA可用来表征复合酸性凝胶的凝胶强度。LA/HA质量配比、pH值和基体浓度对复合酸性结冷胶凝胶的凝胶特性影响显著。随着LA/HA质量配比的增加,EA和k1均表现出先增大、后减小的变化规律,在LA/HA质量配比为50∶50时获得最大值,说明此时LA和HA形成了互穿网络。随着pH值的增加,复合酸性结冷胶凝胶的EA呈现了先增大、后减小的变化趋势,pH值为3时最大。结冷胶总浓度越高,EA越大。相对于高酰基结冷胶,低酰基结冷胶对酸更为敏感。此外,模拟胃液酸环境时,以pH值为2的酸液浸泡可以对复合凝胶的结构与凝胶特性产生影响。

Gelation Properties of Low Acyl and High Acyl Mixed Acid Gellan Gels

Stress relaxation is the result of time-dependent 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/H-GLG)using stress relaxation parameters.Influences of LA/HA weight ratio,gellan concentration and pH value on the gelation properties of L/H-GLG were studied.The results showed that the stress relaxation behavior of L/H-GLG fitted well with Peleg's 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 de-structuring of mixed gellan acid gels can be controlled in acidic environments similar to those that were presented in the stomach after food consumption.