The Research On Thermal Analysis Determining Starch Content In Corn And Rice

Thermal analysis is a technique for studying the physical and chemical changes ofsubstance in the process of heating or cooling.The advantage of quick analysis speed,simplesample pre-treatment and diverse information makes it a common analytical testing means.Inrecent years,the development of science and technology,especially the continuous innovationand improvement of thermal analysis techniques,has made the applications of thermalanalysis constantly widen and objects increased.The samples studied in the food systeminclude water,starch,lipids and proteins and other biological macromolecules,as well as itscomposite system,food organization system is also included.The purpose of this thesis is toestablish a new method which can fast and accurate determination starch content in corn andrice.1.By thermal analysis,the characteristic decomposed range curve of corn is250~370℃,and the rice is250~330℃,then verified by infrared spectroscopy.The endothermic peak incorresponding temperature interval of differential thermal curve is starch,the contentpositively correlated with the peak area.In addition,starch content of rice is also positivelycorrelated with the weight loss rate in the decomposed temperature range of the TG curve.2.The starch content of corn was determined by differential thermal analysis.Optimalexperimental conditions are as follows:heating rate is10℃/min,the filling sample is10mg,theparticle size is80mesh.Measured the starch content and peak area of20corn samples by thenational standard method and the DTA method,The result shows that the correlation equationbetween starch content and the peak area of DTA curve is Y=3.082X-197.6,the coefficientr=0.996.Based on the result of the precision and accuracy experiment, the model built fromthe20samples has a higher accuracy which the error is less than1%.3.Under the optimized conditions,the correlation equation,which is built using the ricestarch standard between pure starch content and the peak area of DTA curve,isY=1.179X+22.99,the coefficient r=0.997.Measured the starch content and peak area of21rice samples by the national standard method and the DTA method,The result shows that the correlation equation between starch content and the peak area of DTA curve isY=14.48X-1114,the coefficient r=0.999.Based on the result of the precision and accuracyexperiment,the value of starch content is lower than true value from the pure starchmodel.The revised DTA measurement results in the allowable error range,and the model builtby the sample measurement error is less than0.5%.4. The starch content of rice was determined by thermogravimetric analysis.The weightloss rate in the range of250to330℃can be obtained on the TG curves by measuring thedifferent concentration of rice starch.The pure starch content and the weight loss rate is builtcorrelation equation:Y=0.5397X+3.598,the coefficient r=0.999.Measured the starch contentand weigh loss rate in the range of250to330℃of21rice samples by the national standardmethod and the DTA method,The result shows that the correlation equation between starchcontent and the weight loss rate in TG curve is:Y=0.5234X+4.683, the coefficient r=0.999.The results of precision and accuracy experiment,we can conclude that the rice starch contenthas no significant difference with the true value by using pure or sample model.Therefore,according to the relevant equations,under the same experimental conditions thestarch content of rice can be measured by the weight lose rate in characterize range.Thismethod is accurate,fast,and has a better practicability.