Study On Mechanism Of Pectinase Modification And Pectin Degradation By Pulsed Electric Fields

The pulsed electric fields is considered to be one of the most innovative and controllable non-thermal processing technologies.The processing effect is excellent,the processing cost is relatively speaking,and it has broad prospects.There have been quite a lot of findings in bactericidal inactivation enzymes and modification of food macromolecules.In the process of enzyme inactivation,it was found that certain action conditions can enhance enzyme activity,but more in-depth research is less.In order to further study the effect of pulsed electric field technology on the modification of biological macromolecules and the production of new modified pectins,this article focuses on the modification of pectinase properties,conformation and promotion mechanism of pectinase activity by pulsed pulses,and proposes PEF-enzyme linkage Use the method of degrading pectin to study the structure of its degradation products,which are mainly embodied as follows:(1)Mild treatment conditions can increase the pectinase activity.The best conditions are an electric field intensity of 7.5 k V/cm and 45 pulses.The enzyme activity of the PEF treatment group was higher than that of the control group within the set temperature and p H range.The modification effect of activation of enzyme activity can be maintained for 12 h.The activation energy,enthalpy change,entropy change,and free energy change of the modified pectinase reaction system are all reduced,the enzymatic hydrolysis reaction rate is accelerated,and the thermal stability is improved.It can be seen from the enzyme kinetic parameters that the maximum reaction rate increases,the Michaelis constant decreases,the enzyme catalytic efficiency increases,and the product conversion efficiency increases.(2)As a result of electric field modification,the secondary and tertiary structure of pectinase will change significantly.When the electric field intensity and the number of pulses increase,the endogenous fluorescence intensity decreases,and the maximum absorption peak red shifts;the ultraviolet absorption intensity first decreases around 280 nm and then when it rises,the absorption peak shifts blue;the fluorescence quenching constant and surface hydrophobicity first increase and then decrease,the surface sulfhydryl content increases,and the total sulfhydryl content decreases;the average radius of pectinase and the polydispersity coefficient first decrease and then increase.It is speculated from the conformational change that the reason for the increase of enzyme activity is that electric field polarization and free radical effects lead to unfolding of pectinase,exposing more active sites.(3)With the increase of the electric field intensity and the number of pulses,free radicals accumulate in the modified system;3 m M ascorbic acid solution effectively removes the generated free radicals.The concentration of pectinase does not affect the optimal modification conditions,and the effect is significant when the concentration is low.Under mild treatment conditions,the amount of free radicals generated in the electric field is small,and electric field polarization is the main reason for the increase in activity;under severe conditions,the activity of pectinase is reduced or even inactivated,and the free radical effect plays a leading role at this time.(4)The optimal combined degradation conditions are determined by the enzymatic hydrolysis rate of pectin,and the efficiency of combined enzymatic hydrolysis is more efficient;the molecular weight,esterification degree,viscosity and average particle size of combined degradation of pectin are significantly reduced.Through structural characterization,it is found that pectin exists as a shorter linear fragment after being degraded by PEF-enzyme combination.The electric field modified pectinase enhances the activity and improves the degradation rate of pectin;secondly,the free radicals generated by the electric field act on the glycosidic bonds of the neutral sugar side chain of pectin and the groups on the main chain to further degrade pectin,providing More enzyme sites.