| Rice starch has got more and more attention because of its physical and chemical characteristics such as delicate taste,digestible,low allergy.However,as with other cereal starches,rice starch also has weak gel strength,poor thermal stability,intolerance of shear,and easily retrogradation.The study found that the addition of dietary fiber can improve the starch-based food texture,water retention and shear resistance properties,enhancing the stability and water holding capacity of the product,thereby can prolong the shelf life of the storage product.The effect of dietary fiber with starch is closely related to its own structure.The molecular weight of polysaccharide is an important factor which affecting the starch-based product functionality.This paper mainly explore the effect of several different molecular weight soluble dietary fiber(soluble soybean dietary fiber,inulin)on the pasting,rheological and retrogradation properties of rice starch.Soybean soluble dietary fibers with molecular weight of 278 KDa for HSSDF and of 9.3 KDa for LSSDF were significantly affected the pasting,rheological and retrogradation properties of rice starch.Rapid Visco Analyzer(RVA)results showed HSSDF increased peak viscosity of rice starch,while LSSDF had no significant effect on peak viscosity of rice starch.Compared with native starch,both HSSDF and LSSDF can improve the initial gelatinization temperature of the mixed system.Rheological results showed that compared with native starch,the storage modulus G ',value of index n and thixotropic fluid loop area of RS-SSDF composite system were all decreased,which means the composite system more stable.At the same time,this two different molecular weight of SSDF could also reduce the short and long term retrogradation of rice starch.Using rheometer,X-diffraction,Differential scanning calorimetry,Fourier transform infrared spectroscopy(fourier transform infrared spectroscopy,FTIR),scanning electron microscopy to study the effect of two different molecular weights of SSDF on rice starch retrogradation properties.Dynamic rheological results showed that: tan? value of all samples decreased with time,however,compared with the starch,tan? value of SSDF have increased,indicated that SSDF could inhibit short term retrogradation of rice stach,and RS-HSSDF's tan? value increased more pronounced.With the extension of days,RS-SSDF's retrogradation enthalpy becomes larger.However,its enthalpy were significantly less than the original starch group,especially of the RS-HSSDF composite system.X-Diffractometer and infrared spectrum further showed SSDF can restrain retrogradation of rice starch.The microstructure showed SSDF can significantly increased water holding capacity of starch gel during aging,so as to effectively retarded the aging of rice starch.In addition,the paper also discusses another soluble fiber,inulin,on the effect of RS pasting,rheological and retrogradation properties.Studies have shown that three different degree of polymerization(SI DP <10,MI 10<DP<23,LI DP> 23)inulin(Inulin)have a significant impact on the rice starch pasting and rheological properties.RVA curves showed three different degree of polymerization of inulin can increase the initial gelatinization temperature of rice starch.Compared with native starch,RS-SI reduces the peak viscosity and RS-MI and RS-LI increased peak viscosity.Rheological experiments showed that adding three different degree of polymerization of inulin can increase the storage modulus G 'of RS and G' values increased with the increase of the degree of polymerization.Compared with native starch,SI and MI can reduce RS consistency coefficient K,while LI allows mixing system consistency coefficient increases,which means the system has a higher viscosity.The three different degree of polymerization of inulin can make a mixed system more stable,especially of SI.In order to further explore the influence of inulin on rice starch retrogradation properties,rheometer,X-diffraction,Differential scanning calorimetry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscope were been used.Dynamic rheological results showed inulin could inhibit the short term retrogradation of rice starch.Three different degree of polymerization of inulin-starch systems retrogradation enthalpy were significantly less than the original starch group,and the composite system retrogradation rate decreases with the decrease of the degree of polymerization of inulin.X-diffraction ?infrared spectroscopy methodMicrostructure observations further proved that inulin can inhibit the retrogradation behavior of rice starch,and the effect were enhanced with the decrease of the degree of polymerization of inulin. |
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