Effects Of Low Molecular Weight Sugars On Propetries Of Tapioca Starch

Effects of low molecular weight sugars (sucrose, glucose and trehalose) on the properties of tapiocastarch (TS) were studied; Structure and energy changes of the low molecular weight sugars-amylose-watersystem were optimized with Hyperchem8.0in this thesis.Pasting, rheological properties and gelatinization kinetics of tapioca starch in the absence or presenceof sugars were investigated by RVA, rheometer and DSC methods. Results showed sugars increased theviscosity and decreased the solid-like characteristics of starch paste; sugars increased the gelatinizationtemperature and the Eavalues, but decreased the rate constants during starch gelatinization and the effectsof disaccharide were more obvious than monosaccharide. Kinetic parameters from the study ofgelatinization kinetics revealed the regulars of the gelatinization of tapioca starch with sugars.This paper described the effects of sugars on the properties of starch gel in freeze-thaw (FT) andrefrigerated cases. The FT stability of TS gels could be improved by sugar addition, according to the sugartype and concentration. And the improvement of syneresis%was in the order: trehalose＞sucrose＞glucose,so trehalose was a good candidate for improving the FT stability of TS gels. The results were also provedby SEM and DSC experiments. Druring cold storage, FTIR showed that sugars restrained theretrogradation of starch and the resisting ability consistented with the FT case. The retrogradation kineticsrevealed the rate constant of recrystallization decreased and the time of half retrogradation increased. Theresults of TPA, light transmittance, DSC, FTIR and kinetics were coincident.Due to the different treatments under the effects of microwave, the pasting and gelatinizationproperties were different with one another. The samples experienced mixing prior to microwave displayedhigher viscosity than the samples experienced microwave prior to mixing. The former had highergelatinization temperature, less gelatinization enthalpy than the latter. The yield stress, consistencycoefficient, loss factor of the former was higher than the latter, but the thixotropy was reduced. Theseresults indicated the interactions of sugars-microwave-starch alerted the mode of interaction between starchand sugar.Through simulating the change of energy and structure of starch-sugar-water system, the effects ofsugars on the gelatinization and retrogradation processes were discussed. Single point energy showedsugars restrained the gelatinization process, and the order of restraint was trehalose>sucrose>glucose; Incooling process, starch with sugar released less energy, and the energies decreased according to the order oftrehalose>sucrose>glucose, which indicated sugars could prevent the ordering of starch structure(recrystallization). QSAR showed that in heating process, the volume and surface areas increased, and thestructural parameters decreased when sugars were added into the system, indicating sugars prevented thechaos of the system; In cooling process, the structural parameters of starch system reduced, and theparameters of starch-sugar systems reduced less, indicating sugars could prevent the ordering of starch, andthe order was still trehalose>sucrose>glucose. These calculated results agreed with the experimental resultsin chapter2-4.