Influence Of Amylose To Cross-linking Reaction And Its Application In Characterization Of Starch

Amylose is one of the most important componenet of starch,which has significant influence to the birefringence of the starch granules,the crystalline pattern,the viscosity of the starch slurry,and the extent of the modification.With the increase of the amylose content,the birefringence,relative crystallinity,and the viscosity decrease,in addition,starches with higher amylose content(>50%)do not show any viscosity.Maize starches are important starch sources for their genetic diversity,and are usually used as the raw materials studied to analyze the influence of amylose content to the experimental phenomenon of the modification Due to the cost effective of cross-linking reaction,it is widely applied in the modification of the physicochemical properties of starches,and it also provides theoretical basis for the preparation of cross-linked starch by studying the effect of amylose content to the cross-linking reaction.Moreover,by analyzing the physicochemical properties of the cross-linked starch and applying it into the determination of properties of the cross-linked starches is of great significance,because studies concerned the cross-linked maize starches are mainly centered on the mechanism of the reaction of normal types,the development of the analytical detection methods and the study of granular polymorphism of maize starches are limited.The different amylose content not only existed in the starch origins,but among the starch granules,therefore,the application of the maize starches' granular polymorphism to the analysis and determination of the physicochemical properties of maize starches,the thermal stability of the cross-linked starches,as well as the factors influencing the viscous behavior of starch paste like degree of chemical modification,concentration,mechanical shear,and gelatinization temperature,which would be very important for the increase of the expansion of starch utility and processing,and also for the development of the cross-linking of starch in practice and theoriesThe present dissertation will focus on the influence of amylose content to the cross-linking reaction,maise starches of genetic and polymorphic diversity are applied as the raw material,the analysis of optical images,thermodynamic analysis,viscous behavior,molecular structure,the interaction of several concerned factors affecting the physicochemical properties of the cross-linked starches are also considered.These researches will broaden the cross-linking reaction and give some new depth into the determination of amylose content and the cross-linking degree of cross-linked starch,additionally,we improved the separation and purification efficiency of irregular granules in high amylose maize starches and get some significative consequence.The main conclusions are listed as followsIn the firtst section,comparisons were made among several ways of determining the cross-linking degree of cross-linked starches and a new way,starch-iodine method,based on the mechanism of the cross-linking reaction,was also carried out.Starches of three crystalline patterns(A,B,and C)were applied as the raw materials to prepare cross-linked starches of varied cross-linking reagent levels(0.01,0.05,0.1,0.5,1,5,10%).With the increase of the cross-linking reagent added,the amylose molecules were cross-linked to the amylopectin,as a result,the free amylose decreased.The starch-iodine method can be applied to characterize the cross-linking degree of the cross-linked starches,based on the ratio of the differences between the absorbance of the native starch and the modified starches to the naticve starch,CL%=(A-?)/?×100%,the results showed that this method had a wide detection range and is of higher simplicity,wide utility.In the second section,normal maize,normal potato,waxy maize,waxy potato of A and B crystalline patterns and normal and waxy genes were studied as the raw material,sodium trimetaphosphate and sodium tripolyphosphate used as the cross-linking reagent,we studied we studied the starch-iodine method in the characterization of the cross-linking degree of waxy starches.In addition,the influence of amylose to the efficiency of the cross-linking reaction(DE=CL%/RL,the ratio of cross-linking degree to reagent level).The results showed that the waxy starches with lower amylose content was found to have higher reaction efficiency,and the starches of A ccystalline pattern with short amylose molecules had a lower reaction efficiency,starch-iodine method can also be applied into the characterization of the cross-linking degree of the waxy starches.The effect of cross-linking reaction was more prominently displayed on the waxy starches,if higher viscosity was needed,the cross-linked waxy potato starches should be a more fascinating choice.Moreover,the destruction of the hydrogen bond energy and construction of the cross-linking bond energy were different,which caused the difference of the enthalpy change between the native and the cross-linked starches.For the normal starches,the destroyed hydrogen bond energy was lower than the newly formed cross-linking bond energy.In the third section,we studied the thermal stability of the chemical bonds and the viscous stability of the cross-linked starches prepared by starches of different amylose content,respectively.Firstly,we studied the thermal stability of the two cross-linking bonds(amylose-amylopectin,and amylopectin-amylopectin)constructed in the cross-linked starches prepared by two different cross-linking reagents(sodium trimetaphosphate,and phosphorous oxychloride).The results showed that,after the cross-linking treatment,the absorbance of the cross-linked starch-iodine decreased with the increase of the water bath temperature.Moreover,at boiling temperature,the absorbance of the cross-linked starch-iodine of all the cross-linked starches were similar to the native maize starch,In the meantime,all the cross-linked starches can still keep a granular outer shapes,indicating that the amylose-amylopectin was thermally unstable and the amylopectin-amylopectin was stable.Then,we studied the joint effects of amylose content,chemical substitution,concentration of the starch slurry,mechanical speed,and the gelatinization temperature to the viscous stability of the cross-linked starches slurries.The starch of lower amylose content(waxy maize)was more inclined to gelatinize and develop a homogeneous starch solution.With the increase of the cross-linking reagent added,the viscosity of the cross-linked starches increased first and then decreased.Native starch gelatinized at proper temperature showed a higher peak and final viscosity than the cross-linked starch.In the fourth section,based on the polymorphic of starch granuels,a method of measuring amylose content by a polarized microscope was developed,and the irregular granules were aloso separated and furified by heat and enzyme treatment.Firstly,the amylose determination involved shooting images of the chosen fields both under normal and polarized light with the same parameter settings(magnification 200 ×,exposure time 400 ms).After processed by IPP-6.0,the statistic results can be obtained quickly by two computer processings,and the amylose content of the waxy maize was considered 0,an equation(ACIOD=ID*/IA*-IOD/IA/IOD*/IA*×100%)was constructed to characterize the amylose content of other maize starches.The results showed a good correlation with the results of the ISO method,which was applied to modify the optical method,Y=-1.433-0.146X+0.018X2,R2=0.9703.Then,the maize starches of different genotypes including waxy maize,normal maize,and two high amylose maize starches(HYLON V and HYLON ?)were treated with boiling water bath for different time periods(10,30,60 min)and then starch hydrolyzing enzymes(mixture of a-amylase and glucoamylase).The irregular starch granules of heat resistant and enzymatic resistant starches were collected.Then the irregular granules was cross-linked and compared with the cross-linked starches prepared by the native high amylose maize starch,the swelling power of the irregular granules was higher than the native granules and its cross-linked starches,however,with the increase of the corss-linking reagent level,the swelling power also increased.The results showed that there were two different mechanisms influencing the swelling power of the cross-linked high amylose maize starches that operate in opposite directions.On the one hand,after the random cross-linking of the cross-linking bridge inside the amorphous region of starch granules,the swelling of the granules became difficult and will diminish the swelling power.On the other hand,the increase of the phosphate groups caused the increase of the hydrophilicity of the modified starch granules,this was for the reason of the negative electric charge of the phosphate groups.