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Effect and Kinetics of Microwave Degradation of Pectin on Its Rheological Properties
This paper, by a researcher from the State key Laboratory of Food Science and Technology of Nanchang University, discusses the effects of microwave degradation of pectin on its rheological properties and kinetics, and is published in the important journal Food Science.
Rheological properties and kinetics of pectin solutions of different mass concentrations (0.5, 1.0, 1.5, 2.0 g/100 mL) after microwave treatment at different times (0, 1, 3, 5, 8, 15, 20, 30 min) Inspection. The results showed that the apparent viscosity and intrinsic viscosity [η] of the samples decreased with the decrease of the mass concentration of pectin solution, the prolongation of microwave treatment time and the increase of shear rate. The Newtonian power law equation is used to describe the fluid behavior of the solution. The pectin solution is a shear-thinning pseudoplastic non-Newtonian fluid. At low mass concentrations, microwave treatment has the greatest influence on the fluid behavior of the solution.
The microwave degradation of pectin followed the first order kinetics according to the intrinsic viscosity. The degradation rate of pectin was the fastest at 0.5g/100mL concentration and the slowest at 1.5g/100mL concentration. Compared with the blank group without microwave in boiling water bath, it was found that there was non-thermal effect in the degradation of pectin by microwave.
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The shear rate scanning diagram shows that the apparent viscosity of pectin solution decreases with the increase of shear rate, the decrease of mass concentration and the prolongation of microwave treatment time. The Newtonian power law fitting shows that the apparent viscosity of pectin solution decreases with the increase of shear rate. Under the condition of low mass concentration (0.5g/100mL), microwave treatment of pectin has the greatest effect on the fluid behavior of the solution, and at higher mass concentration (1.5g/100mL), Microwave treatment of pectin makes the fluid behavior deviate from the ideal Newtonian fluid.
The degradation of pectin under microwave condition is not only due to the thermal effect, but also to the non-thermal effect of microwave. What kind of non-thermal effect leads to the degradation of pectin, and the degradation mechanism remains to be further studied.
The pectin was dissolved in 100 mL of distilled water to prepare a pectin solution with a concentration of 0.5, 1.0, 1.5, 2.0 g/100 mL, dissolved completely, transferred to a three-necked flask, and condensed water was turned on at 680 W, 100 ° C. Under microwave conditions (XH-200A, Beijing Xiangyu Technology Development Co., Ltd.), they were treated for 1, 3, 5, 8, 15, 20, 30 min and lyophilized. The boiling water bath was set without microwave, and other pectin solutions with the same conditions were blank control group.