Effects Of Enzymatic Modification On Physicochemical Properties Of Waxy Rice Starch

The enzymatic modification was used as a clean label in the starch modification method,and starch structure was modified by a branching enzyme to obtain fine physicochemical properties to obtain economic benefits.Starch branching structure has a significant effect on starch physicochemical properties.The starch product has certain economic benefits.The predecessors have done research of branching enzymes to modify the starch,but it is of great significance to useα-amylase and branching enzymes to modify the glutinous rice starch to improve the transglycosylation efficiency of branching enzymes.In this study,the waxy rice starch was modified byα-amylase co-branching enzyme,and the physicochemical properties of the modified waxy rice starch were studied.wheat amylose,corn amylose,rice amylose and maltose was mixed with waxy rice starch,respectively,and thenα-amylase was used to hydrolyse the mixture to produce some intermediate chains,and finally branching enzyme catalysed the intermediate chains by transglycosylation..The main research results:1、The surface morphology and polarization cross of the modified starch and waxy starch were observed by SEM and polarized light microscopy.The polarized cross of granular modified starch still existed,while the polarized cross of gelatinized modified starch disappeared.The surface of waxy rice starch was smooth and the surface of granular modified starch maintains the basic starch morphology,only the surface was wrinkled.The gelatinized starch surface was cotton-like.2、Fourier transform infrared spectroscopy（FTIR）and deconvolution spectroscopy were utilized to analyze the short-range starch structure changes between waxy rice starch and modified starch.The intensity ratio at 1047cm^-1/1022cm^-1 of the modified starch was higher than that of the original starch,however the gelatinized modified starch in 1047cm^-1/1022cm^-1 peak intensity ratio is lower than that of granular modified starch.Extending branching enzyme action time can improve the short-range order structure of the modified starch.Increasing the hydrolytic enzyme can improve the short-range order structure of the modified starch.3、The degree of branch was analyzed by liquid nuclear magnetic resonance spectroscopy（¹H-NMR）.The degree of branching of the granular modified starch exceeded the gelatinized modified starch and waxy rice starch;Usingα-amylase as the prerequisite enzyme,the degree of branching（DB）of modified starch can be increased.The high degree of branching（DB）of gelatinized modified starch by adding the amylose was wheat amylose,and the high degree of branching（DB）of granular modified starch by adding the amylose was maize amylose.4、The degree of crystallinity of the modified starch is reduced to varying degrees compared to the original starch,and the crystal changed form crystalline A to crystalline V;Granular modified starch was crystalline A,only a characteristic diffraction peak at position 17°and 18°,which changed from a double peak to a single peak;The degree of crystallinity of the starch modified by dual-enzyme method is higher than that by branch enzyme.The high degree of crystallinity of modified starch by adding wheat amylose and maltose.5、The solubility of granular modified starch was lower than that of gelatinized modified starch,and the turbidity of granular modified starch was higher than that of gelatinized modified starch;Increasing Branch enzyme action time,turbidity and solubility have declined to varying degrees;Addition ofα-amylase as a prerequisite enzyme can reduce the solubility and turbidity of modified starch;The low degree of turbidity of gelatinized modified starch by adding maltose,and the low degree of turbidity of granular modified starch by adding rice amylose starch.6、The gelatinized modified starch does not have gelatinization characteristic peaks on the map.While the gelatinization enthalpy（ΔH）of granular modified starch was more than the gelatinization enthalpy（ΔH）of waxy rice starch.Extending the action time of branching enzyme,theΔH occur different degree of increase.Branching enzyme action time was 12h,the high gelatinization enthalpy（ΔH）of modified starch by adding wheat amylose starch.Branching enzyme action time was 24h,the high gelatinization enthalpy（ΔH）of modified starch by adding maltose.7、G’and G"of granular modified starch was higher than original starch,and G’>G";G’and G"of gelatinization modified starch was low than original starch,and G’<G";Granular modified starch loss factor（tanδ）decreases with increasing frequency（ω）.Branching enzyme action time was 12h,as the frequency（ω）increases,the loss factor（tanδ）rises first and then decreases;while branching enzyme action time was 24h,the loss factor（tanδ）increased with increasing frequency（ω）.