微波降解果胶对其流变性质的影响及动力学

摘要

对不同质量浓度(0.5、1.0、1.5、2.0 g/100 mL)的果胶溶液微波处理不同时间(0、1、3、5、8、15、20、30 min)后的流变性质及动力学进行考察.结果表明,随着果胶溶液质量浓度降低、微波处理时间延长、剪切速率增大,样品的表观黏度和特性黏度[η]均降低.用牛顿幂律方程描述溶液的流体行为,果胶溶液是剪切稀化的假塑性非牛顿流体,在低质量浓度时,微波处理对溶液的流体行为影响最大.根据特性黏度对样品进行反应动力学拟合,发现果胶的微波降解遵循反应一级动力学,在质量浓度0.5 g/100 mL时降解速率最快,质量浓度1.5 g/100 mL时降解速率最慢.经与沸水浴无微波的空白组对比,发现微波降解果胶的过程还存在非热效应.%The rheological properties and degradation kinetics of pectin at various concentrations (0.5,1.0,1.5 and 2.0 g/100 mL)subjected to microwave treatments for different time periods (0,1,3,5,8,15,20 and 30 min) were assayed.The results showed that both the apparent viscosity and intrinsic viscosity [η] of the samples decreased with the reduction of pectin concentration,and with the increase of microwave processing time and shear rate.Using power law equation to describe their rheological behaviors,the pectin solutions were a share-thinning non-Newtonian fluid.Microwave treatment had the greatest impact on fluid behavior at low concentrations of pectin.The microwave-induced degradation of pectin was fitted based on [η] to a first-order kinetic model,and pectin at 0.5 g/100 mL was degraded fastest and at 1.5 g/100 mL slowest.Compared with the samples subjected to boiling without microwave treatment,microwave treatment also had non-thermal effects in pectin degradation.