Physicochemical Characteristics And Molecular Structure And Their Correlation In Rice Starch

Molecular distribution, physicochemical properties and pasting properties of rice starch from different types were studied by Rapid Visco-analyzer (RVA), laser light scattering, Gel Permeation Chromatography. Result indicated:1. Molecular distribution of rice starchRice starch has 3 main fractions, amylose, intermediate and amylopectin. Relative molecular weight of rice amylopectin is about 49. 67×10~6g/mol～ 957. 69×10~6g/mol, while rice amylose is about 1. 90×10~6g/mol ～5. 91×10~6g/mol. The molecular weight distribution of rice amylopectin is narrower than that of rice amylose. Amylose, intermediate and amylopectin account for 11. 52～48. 62%, 28. 74～69. 33% and 6. 26～40. 77%, respectively.2. Physicochemical properties of rice starchBlue value and enzyme hydrolysability differed from different rice starches. The blue value of indica rice starch was greater than that of japonica and glutinous rice starches, while the enzyme hydrolysability of japonica and glutinous rice starches were greater than that of indica rice starch. Granularity of rice starch, whose dimensional appearance was hexahedron or globe, 2～6μm, could be well simulated by function Rosin-Rammler distribution.Gel texture plot differed from different rice starch gel. Gel texture properties were greatly influenced by blue value and enzyme hydrolysability, which could be described by an exponential model.Paste curve differed from different rice types, instead of different rice varieties. Pasting parameters was greatly affected by blue value and enzyme hydrolysability, which could be described by an exponential model. Hot paste stability of indica rice starch was better than that of japonica and glutinous rice starches, while cold paste stability of japonica and glutinous rice starches were better than that of indica rice starch.3. Solution properties of rice starchRice starches paste was pseudoplastic. Viscous coefficient and rheologic indexes were obviously influenced by varieties, temperature and concentration of rice starches paste. As the temperature increased, the consistency coefficient of rice starch paste decreased and flow behavior index were inclined to invariableness. As concentration decreased, consistency coefficient of rice starch paste decreased and flow behavior index increased slightly. Intrinisic viscosity for rice starch of low concentration in DMSO was greater than that of amylose. Relationship between intrinisic viscosity and average...