Effects Of Starch And Protein Components In Glutinous Rice Flour On Its Gelatinization Properties

Glutinous rice flour has a broad market for food processing.Starch and protein,as the two highest components in glutinous rice,have a very important impact on the physical and chemical properties and processing characteristics of glutinous rice flour,but the specific effects and mechanism are not clear.In this study,taihu japonica glutinous rice was used as experimental materials.After storage under different conditions,the storage protein components of glutinous rice powder were removed in order to study the effects of different types of protein on the characteristics of glutinous rice paste.Futhermore,protein and lipid were removed to study the effect of starch fine structure change on starch gelatinization characteristics in glutinous rice flour.The effect of starch and protein on gelatinized gel quality was further studied in order to provide theoretical basis and guidance for the processing and utilization of glutinous rice flour.(1)The effect and mechanism of protein on gelatinization properties were explored.The results showed that the removal of gluten and globulin can significantly reduced the peak viscosity,breakdown and setback of glutinous rice flour samples,and the removal of prolamin also had a great impact,and the effect of proteins in the samples stored at 35? was more significant.The protein subunit with molecular weight between 12 and 35 kDa was the main factor affecting the gelatinization characteristics of samples.After the storage proteins were removed successively,the wrapping and limiting effect of proteins in glutinous rice flour on starch was weakened.After the removal of globulin,the sample gradually changed to the state of small particle aggregation,and after the removal of gluten,the sample changed to the state of small particle dispersion,and the particles had been close to the pure starch.After the removal of globulin and gluten,the hydrogen bond between protein and starch system in the sample was weakened,the protection of protein to starch was weakened,and the starch was more likely to break,the swelling force was reduced,and the viscosity in the gelatinization process was reduced as a whole.In addition,the removal of globulin,gluten and prolamin significantly reduced the capacity of starch to hold and bind water,and weakened the water absorption capacity of starch during the heating and expansion process,resulting in the overall decrease of the viscosity curve of the sample.With the increase of storage aging degree,the hydrogen bond force between starch and protein increases,and the influence of gelatinization characteristics,binding water capacity and swelling degree during heating process was opposite to that of protein removal.(2)The effect and mechanism of starch fine structure on starch gelatinization characteristics in glutinous rice flour were investigated.The results showed that with the increase of storage temperature and time,the peak viscosity,trough viscosity,breakdown,final viscosity and setback of starch samples increased significantly,while the gelatinization temperature and peak time did not change significantly.With the increase of storage aging,The molecular weight of amylopectin showed a decreasing trend,and the distribution was more dispersed;the molecular weight of amylose showed an insignificant increase trend,and the distribution became aggregated.The average chain length and internal chain length of amylopectin were significantly reduced,and the crystallinity of the sample was reduced.The starch gelatinization parameters had a significant correlation with the Mw and Mn of starch amylopectin and the Mn of amylose,and it also had a high correlation with the Mw of amylose.In amylopectin structure,?-amylase hydrolysis rate,average chain length and internal chain length were negatively correlated with peak viscosity,trough viscosity,breakdown,final viscosity and setback.The crystallinity of samples was negatively correlated with peak viscosity,trough viscosity,breakdown,final viscosity and setback.After storage,the internal ordered and disordered structure of glutinous rice starch did not change significantly,but the enhancement of intramolecular hydrogen bond made the starch structure closer,resulting in the reduction of solubility,the increase of swelling power and the overall increase of starch gelatinization viscosity.(3)The effects of starch and protein on the rheological and texture properties of glutinous rice flour gelatinized gel were explored.The results showed that the removal of gluten and globulin can significantly reduced the elastic modulus and viscosity modulus of the glutinous rice flour sample,increased the tan? and increased the overall viscosity ratio,and storage at 35°C made the protein in the sample more significant.The increase in storage aging changed the rheological properties of starch gelatinized gel.After storage,the springiness and viscosity of starch gel increased simultaneously,tan? decreased,and the overall viscosity ratio reduced.The increase in storage aging made the gelatinized gel of starch and glutinous rice flour had higher hardness,adhesion and springiness,and the texture index of glutinous rice flour changed more.After removing globulin and gluten,the hardness,adhesion and springiness of glutinous rice flour were significantly reduced,and storage at35°C made the influence of protein in the sample more significant.Principal component analysis results: the protein subunits in the low molecular weight range(12-35 kDa)had an important impact on the rheological properties(K',n',K ",n")and texture properties(hardness,adhesion,springiness).The molecular weight of amylose and amylose in starch,especially the molecular weight,average chain length,and internal chain length of amylopectin had an important influence on the rheological properties(K')and texture properties of starch gelatinized gels(Hardness,adhesion,springiness,resilience).