The Study On The Degradation Of Pectin By Microwave And Microfluidization

As a natural additive,pectin often used in the food industry as gels,thickener,stabilizer and emulsifier.Pectin has been widely used in medicine and cosmetics industry,but the complicated and varied processing environment will lead to the degradation of pectin which changes its functional properties and affects its application.Therefore the degradation of pectin draw public attention of scholars at home and abroad.This article mainly study rheological properties and kinetics of apple pectin treated by microwave,and research the effect of its conformation.Treated citrus pectin by DHPM at different pH,discusses the influence of pH on the DHPM degradation pectin.The rheological properties and kinetics of pectin that microwave treated at various mass concentrations(0.5,1.0,1.5 and 2.0 g/100 mL)for different time period(0,1,3,5,8,15,20,30 min)were assayed.The results showed that both apparent viscosity and intrinsic viscosity [η] of samples decreased with the reduction of pectin mass concentration,and increase of microwave processing time and shear rate.Using Power law equation to describe the rheological behaviors of solution,pectin solution was share-thinning,non-Newtonian fluid.At low mass concentration of pectin solution,microwave processing has the greatest influence on fluid behavior.Reaction kinetics was fitted based on [η] of pectin.It was found that the microwave degradation of pectin followed first order kinetics reaction,the rate of degradation was fastest at mass concentration of 0.5 g/100 mL,and the slowest at 1.5 g/100 mL.After comparing with the samples that was boiled but without microwave,it was found that there was nonthermal effect in the process of microwave degradation of pectin.Studying the effect of microwave treated on conformation of the apple pectin,through the intrinsic viscosity and SEC-MALLS measured that the chain conformation of apple pectin is random coil in NaCl solution.Treated a short time by microwave has no effect on the chain conformation,when processing after 30 min,the conformation turn to a rigid rod.The effects of pH on the degradation of citrus pectin induced by DHPM were investigated,the degree of degradation of pectin induced by DHPM increased with the increased of acid and alkali.It was found that at acid condition,the molecular weight,intrinsic viscosity and particle size value decreased with decreasing pH,at alkali condition,molecular weight has no changed nearly,intrinsic viscosity rose before reduced,particle size value increased with increasing pH.Environmental scanning electron micrograph showed that the addition of acid and alkali destroyed the microstructure of pectin,with holes and filaments,the structure is more dense.However,the amount of reducing sugars increased with increasing of acid and alkali,it indicated that glycosidic bond ruptured during DHPM processing pectin,and at acid condition,along with disaggregation.By UV scanning,the absorption peak at 285 nm removed,may occur to the modification of the degree of esterification or the ester hydrolysis.