Study On The Preparation Technology Of Arrowhead Resistant Starch By Synergistic Effect Of Ultrasonic And Enzyme

The starch content of arrowhead is high,accounting for about 50%of the dry matter mass of arrowhead tuber,which is a good raw material for the preparation of resistant starch.At present,there is no report on the preparation of arrowhead resistant starch by coordination of ultrasonic and enzyme method.In this study,arrowhead starch was used as raw material to prepare arrowhead resistant starch.In order to solve the problem of low efficiency of enzymatic hydrolysis in the process of preparing resistant starch by enzymatic method and improve the yield of arrowhead resistant starch,Synergism of multi-mode ultrasonic technology and enzyme hydrolyzed arrowhead starch to prepare arrowhead resistant starch.Optimization of preparation technology of arrowhead resistant starch and study on the structure,physicochemical properties and enzymatic hydrolysis of arrowhead resistant starch were done.The main conclusions are as follows:(1)Single factor experiments were done to investigate the effects of enzyme addition,enzymolysis time,ultrasonic time,ultrasonic power,ultrasonic frequency and ultrasonic interval ratio on the yield of arrowhead resistant starch.The kinetic models for the preparation of resistant starch by two methods were established.Based on the results of single factor experiments,enzyme addition,enzymolysis time and ultrasonic time were selected to design the response surface experiment.The best technological conditions of the preparation of arrowhead resistant starch by enzyme coordinated with ultrasonic method were as follows:27.24 npun/g(starch)of enzyme addition,21.07 h of enzymolysis time and 7.40 min of ultrasound time.The predicted value of the yield of resistant starch is 24.17%,and the measured value of the yield of resistant starch is 24.01%.(2)The molecular weight distribution,particle size distribution,apparent structure,crystal type and crystallinity and short-range order of arrowhead resistant starch were studied.The results of molecular weight distribution analysis showed that a large number of short linear starch molecules were formed due to the breaking of the molecular chain of the treated starch samples.The particle size of arrowhead resistant starch samples was increased.The scanning electron micrographs of arrowhead starch sample showed that particles were small with different sizes.The particles were elliptical or irregular with smooth surface and some bulges and depressions.The scanning electron micrographs of arrowhead resistant starch samples showed that the original particle structure was destroyed,and the particle morphology was rough,irregular and different in size.Arrowhead resistant starch samples showed block and compact structure.The crystal type of arrowhead resistant starch samples was changed from A-type of arrowhead starch to B-type.In the infrared spectrum,the positions of the characteristic absorption peaks of arrowhead resistant starch samples were basically unchanged,without the formation or loss of new chemical bonds and functional groups.The short-range order of arrowhead resistant starch samples was increased.The crystal structure of arrowhead resistant starch sample by enzyme coordinated with ultrasonic method was more stable.(3)The thermal properties,absorbency of the starch-iodin,solubility,swelling power,transparency,water holding capacity and enzymatic hydrolysis of arrowhead resistant starch samples were studied.The results showed that the thermal stability,solubility,transparency and water holding capacity of the treated starch samples were increased,the transition temperature,polymerization degree and swelling power were decreased.The results of enzymolysis characteristics showed that the content of rapidly digestible starch and resistant starch was increased of starch sample prepared by coordination of ultrasonic and enzyme method,while the content of slowly digestible starch was decreased.The k value of resistant starch samples prepared by enzyme method and coordination of ultrasonic and enzyme method fitted to the first-order kinetic equation was larger than arrowhead strarch sample,indicating that the speed of starch digestion in vitro to C_?was faster.The C_?value was decreased.It is possible that a large number of short linear starch molecules were produced by enzymolysis and ultrasonic,and the interaction was enhanced to form a dense double helix structure,which limited the digestion degree.