| Starch as an important food raw materials and additives are widely used in allareas of food processing. The characteristic of the original starch is limit and simple.To meet the needs of the different processing and improve the product performance,in actual production, starch is often modified or added exogenous substances.Research shows that adding modified starch in an appropriate ratio can obviouslyimprove the quality of food made with starch. At the same time, it can improve thestability of the product, control water mobility, reduce the production cost andsimplify the process.Raw material of this research is rice starch and hydroxypropyl starchcross-linked tapioca starch (HP-CLTS). In order to promote the quality of riceproducts, improve the products processing and guide rice products development,property of rice starch/HP-CLTS mixed system studied in this study. And discussionmechanism of rice starch/HP-CLTS mixed system change. The main results in thepaper were included as follows.The viscosity property, thermal property, swelling power, solubility index andapperarance of rice starch/HP-CLTS mixed system were determined. The resultsshowed that gelatinization curve of rice starch in the presence of HP-CLTS have noobvious changes. Compared with rice starch system, the pasting curves showedpasting temperature and setback were decreased, while peak viscosity, hot pasteviscosity, cold paste viscosity and breakdown were increased with addition HP-CLTS.The results of the thermodynamic properties showed when the ratio of rice starch toHP-CLTS was10:2, samples had the lowest TO, TCand gelatinization enthalpy value.During gelatinization, swelling power and solubility index of rice starch in differentratio of HP-CLTS were increased with temperature. That’s because theintermolecular force of rice starch and HP-CLTS system is reduced mainly by theinfluence of hydroxypropyl steric hindrance and hydrophilic groups. Gelatinization ismore likely to swell and expand. Adding HP-CLTS, samples particles will lose its polygons structure and starch gel form network structure at low temperature.Meanwhile, the system added HP-CLTS were allowed more water molecules to bepermeated into starch molecules, starch molecules were more likely to be dissolutedand starch particles will be more easily dissolved in solution and form networkstructure. The mixed system G’ decreased, but G’’ increased. In addition, as theproportion of HP-CLTS increased in the mixed system, the consistency coefficient Kwas decreased and fluid behavior index n increased, indicating that the behavior ofstarch gel tended to Newton fluid.Secondly, in the paper, combined texture, amylose leaching, DSC, XRD, FTIR tostudy the short-term and long-term retrogradation of rice starch. Hardness of ricestarch decreased with addition content increased. HP-CLTS could significantly inhibitthe hardness of rice starch increase during storage. Samples which were stored for7days, amylose leaching analysis showed that HP-CLTS could significantly inhibit theformation of hydrogen bonds between inter-and intra-starch molecular chains.Thermodynamic characteristics analysis showed that HP-CLTS could decreaseretrogradation enthalpy of the mixed system. X-ray diffraction and FTIR results alsoshowed that HP-CLTS could inhibit the formation of the crystalline structure duringrice starch aging.This paper was further investigated the moisture distribution of ricestarch/HP-CLTS system during aging. HP-CLTS could improve water-holding ability,and make starch gel keep more water content and water activity. The ricestarch/HP-CLTS system retrograded for7days at4℃after freeze-dryed showed thatHP-CLTS inhibited that water loss from the gel. Low field nuclear magneticresonance relaxation time also suggested that HP-CLTScould inhibite theretrogradation of starch. HP-CLTS delayed the declining of T22and caused areduction in the loss of water. The mixed system remained high liquidity mobility. |
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