Abstract: 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.

Key words: pectin, microwave, degradation, rheological properties, intrinsic viscosity, kinetics, non-thermal effect