Material And Structure Basis For Typical Rice Products Texture And Digestion Properties

The rice varieties with different amylose content were used as model materials in this study,its rice starch were extracted by alkali method.The multi-structure of rice starch was studied by high performance anion exchange chromatography?HPAEC?,gel permeation chromatography?GPC?,small angle X-ray scattering?SAXS?,X-ray diffraction?XRD?,¹³C solid nuclear magnetic resonance,and scanning electron microscopy?SEM?.The thermal,viscosity,rheological and digestion properties of rice starch were studied by differential scanning calorimeter?DSC?,rapid viscosity analyzer?RVA?,as well as other physical and chemical methods.Then,the texture and digestion properties of typ ical rice products such as cooked rice and rice noodle were studied,the digestion curves of cooked rice and rice noodle were fitted by the first order enzyme kinetic equation,and the digestion rate was fitted by LOS?Logarithm of Slope?.The texture characteristics of c ooked rice and rice noodle were characterized by texture analyzer.The purpose of this study is to reveal the material and structural basis for digestion and texture properties of typical rice products.The mainly results were as follows:?1?The chain length distribution curves of amylopectin present typical double peak distribution,while amylose chain length distribution is more wider,the amylopectin weight and molar based chain length of rice starch with different amylose content were significantly different at the molecule structure level;the relative crystallinity of rice starch increased with the increase of amylose content,the SAXS scattering intensity decreased,the proportion of single and double helix decreased,the proportion of amorphous region increased at aggregation structure level;the grain size of different rice starch was 2-7?m,polyhedron and irregular shape were observed at the grain structure level.?2?The relationship between physical and chemical properties of rice starch multi-scale structure was analyzed by pearson and spearman correlation analysis.The swelling power of rice starch was negatively correlated with amylose content,short and medium amylose content.Solubility was positively correlated with short amylose content.Peak viscosity and setback were positively correlated with amylose content,short,medium and long amylose content.Trough viscosity and final viscosity were positively correlated with amylose content,short,medium amylose content.Breakdown were negatively correlated with amylose content,short,medium amylose content,XAP1 and XAP2.Initial and peak gelatinization temperature were positively correlated with f?b₁,negatively correlated with fb₂.Enthalpy was negatively correlated with H_AP2.?3?The relationship between texture and digestibility of rice and chemical composition of rice showed that the hardness of cooked rice was positively correlated with amylose content and medium long chain amylose content,and rice chewiness was positively correlated with amylose content,medium length,short amylose content and X_AP2,and negatively correlated with H_AP2/AP1.The resilience of cooked rice was positively correlated with amylose content and medium long amylose content,but negatively correlated with H_AP2/AP1 and fb₂.There was a positive correlation between the adhesiveness and amylose content,short chain,medium long chain and long chain amylose content.The final digestibility of starch in rice was negatively correlated with amylose content,short chain and medium long chain content,and the digestibility rate was positively correlated with the rice starch branching degree.Protein content did not affect the digestion of rice starch.?4?Different processing have a significant effect on the digestibility of rice products.Rice starch has higher digestibility ratio and faster digestibility rate.The rice noodle and the retrogradation rice noodles are denser and the digestion rate is lower than that of the starch and rice flour.After retrogradation,the digestibility of rice noodle has a decreasing trend.The higher amylose content,the lower the digestibility of rice products?rice noodle?.Protein and fat can reduce the digestibility of rice starch,but have no signif icant effect on digestibility rate.Rice noodle with high amylose content has higher hardness and better elasticity.When amylose content is relatively low,its adhesiveness is strong,so it is not suitable for making rice noodles.