低酰基结冷胶-果胶复配体系的性能

利用质构仪和流变仪对低酰基结冷胶(low acyl gellan,LA)和果胶复配体系的胶体质构和流变性能进行研究。考察不同种类离子(Ca~(2+)、K~+)、离子浓度(0、2、4、6、8、10、20、40 mmol/L)以及LA和果胶不同质量比(100:0、75:25、50:50、25:75)对复配体系质构特性的影响。结果表明,随着离子浓度的增加破坏应力先增大,当达到临界值后开始减小,二价离子(Ca~(2+))的作用效果要强于一价离子(K~+)。复配胶破坏应力随LA比例降低先增加后减少,质量比在75:25时具有显著协同效应。复配体系的黏度随剪切速率增大而减小;当剪切速率相同时,黏度随LA比例的增加而增加,离子种类和浓度对复配体系黏度的影响与质构特性一致。随着温度的升高,复配体系黏度减小,在相同温度条件下,结冷胶与果胶质量比75:25时,体系的黏度最大。储能模量G’大于相应质量比损耗模量G",且G’和G"随LA比例的增加而增大,说明体系的黏性和弹性随LA比例增加而变大。

Properties of Low Acyl Gellan and Pectin Mixtures

The rheological and gel properties of low acyl gellan (LA) and pectin mixtures were studied using a rheometer and a texture analyzer. The effect of different ions (potassium and calcium), different ion concentrations (0, 2, 4, 6, 8, 10, 20, 40 mmol/L) and different LA-to-pectin ratios (100:0, 75:25, 50:50 and 25:75) on mixed gels was investigated. The results showed that calcium ion had a greater effect on failure stress than potassium ion. Failure stress increased with increasing calcium or potassium ion up to the critical level, and then it decreased with further increase in ion concentration. Failure stress of mixed gels increased with decreasing proportion of gellan gum. The strongest interaction occurred when the ratio of LA to pectin was 75 to 25. The viscosity of mixtures decreased with increasing shearing rate. At a content shearing rate, the viscosity was enhanced with increasing LA ratio. Ion type and concentration had identical effects on the viscosity and texture of LA-pectin mixtures. The viscosity was decreased with increasing temperature. For each investigated temperature, the maximum viscosity was observed at a ratio of 75:25. The dynamic rheological results revealed that the storage modulus of mixed gels was greater than the loss modulus, and both of them rose with the increase in LA ratio, indicating that the viscosity and elasticity of mixed systems increased with increasing LA ratio.