Effects Of Hydrothermal On The Physicochemical Properties Of Starches

Starch is an important plant resourc, is widely used in food, chemical, textile andbuilding industries. By physical, chemical or enzymatic means, the original properties ofstarches are improved, applications of starces are widening. Therefore, it is necessary to studythe structures and properties of modified starch to provide theoretical basis guidance on theexploitation and utilization of modified starch. In this paper, normal maize starch, highamylose maize starch, potato starch and mung bean starch had been selected as the specimensto systematically analyze the effect of heat-moisture treatment and annealing on the particlemorphology, particle size, crystallization properties, gelatinization characteristics, and in vitrodigestibility of different starches, as well as the relationship between structure and propertiesof different starches. The main conclusions are as follows:HMT factors (HMT temperature, time and moisture content) have effect on theproperties of normal maize starch. After HMT, the solubility, swelling and transparency ofmodified starch were less than that of native starch, with the increasing of HMT temperature,transparency was reduced. HMT temperature, time and moisture content significantly affectthe RS (resistant starch) content. Increasing HMT temperature or moisture content, the RScontent of maize increased. Extending HMT time, RS content first increased and then decreased.After HMT (moisture content30%, temperature120℃, time10h), the particlemorphology of different starches (normal maize, high amylose maize, potato and mung bean)have different changes. Granule shape changes happened in some part of potato starch andmung bean starch, potholes and breaking were observed in some starch granules. But afterHMT, polarized cross did not significantly change. After HMT, different starches havedifferent variation on crystal structure. The crystallinity and peak strength of maize starchdeclined, but crystal type has not changed, still A. The crystallinity of potato starch decreased,and crystal type changed from B into A+B. Compared with the native starch, the solubility,swelling and transparency of different starches reduced after HMT. HMT can increase the RScontent of starches, and this is related to the increase of amylose content. After HMT, the Pt ofdifferent starches increased, while PV, TV and Bv decreased. The FV of maize starch andmung bean starch increased, while the potato starch decreased.Annealing factors (annealing temperature, time and moisture content) have effect on the properties of normal maize starch. After annealing, amylose content of modified maize starchwas higher than the original. Increasing the annealing temperature or moisture content, orextending the annealing time, amylose content increased. After annealing, the RS content washigher than nature starch. The RS content was increased as the increasing of annealingtemperature. As the increasing of moisture content or extending of annealing time, the RScontent first increased then decreased. The solubility, swelling and transparency of modifiedstarch were less than that of native starch.There was little change on the particle morphology of different starches after annealing(moisture content75%, temperature50℃, time48h). But potholes were observed on thesurface of mung bean starch. Polarized cross did not change. After annealing, particle sizerange of different starches did not change. The small particles were increased in maize starchand high amylose maize starch, big particles were decreased in mung bean starch and potatostarch, but the rate of increase was not great. After annealing, crystal structures of differentstarches have few changes, but the crystallinity of potato decreased. After annealing, thesolubility, swelling and transparency of different starches decreased. Annealing can increasethe RS content of starches, and this is related to the increase of amylose content. Afterannealing, the Pt of different starches increased, while PV, TV, Bv and FV decreased.The effect of hydrothermal on the physicochemical properties of different starches hasbeen studied in this study. Also, the relationship between the molecular structure andphysicochemical properties of different starches has been revealed. These results will providethe basic theory for developing and using of starches resources.