| Sorghum is rich in polyphenols,and part of polyphenols and sorghum starch exists in the form of compounds,to clear this part of the endogenous polyphenols effects on sorghum starch and its interactions with the sorghum starch,this thesis in sorghum starch and its structure features of polyphenols compounds,physical and chemical properties,digestive characteristics were studied.The main research contents and results were as follows:1.Ethanol solvent extraction method was used to optimize the separation conditions of sorghum starch-polyphenol complex（complex）.Under the optimal separation conditions,sorghum starch and sorghum polyphenols were obtained,and the components of sorghum polyphenols were determined and analyzed by HPLC performance liquid chromatography.The results showed that the extraction yield of sorghum polyphenols was 42.48%under the following conditions:extraction time of 30 min,extraction temperature of 35℃,ethanol volume fraction of 60%and solid-liquid ratio of 1:25.Sorghum polyphenols mainly contained gallic acid,coumaric acid,catechol and ferulic acid,and their contents were 0.26μg·g-1,0.30μg·g-1,0.16μg·g-1and 160.76μg·g-1,respectively.Ethanol solvent extraction method can effectively separate the complex,and also determine the composition and content of sorghum polyphenols.2.The crystal types,functional groups and other structural characteristics of sorghum starch and its polyphenol complexes were studied by X-ray diffrotometry and near infrared spectroscopy.The results showed that the surface of starch particles was smoother and the particle size was larger than that of starch,but the amylose content,p H and iodine binding force of the compound decreased by 11.06%,4.17%and 25%,respectively.The X-ray diffraction peak shape and near infrared spectrum absorption peak shape remain the same,but the crystallinity and order degree of the complex decrease by 1.24%and 0.15,respectively.Sorghum polyphenols mainly bonded with sorghum starch through non-covalent bonds such as hydrogen bond to form complex.3.The solubility,viscosity and thermodynamic properties of sorghum starch and its polyphenol complex were compared.The results showed that the solubility of the compound was0.37%～5.25%higher than that of starch,and the swelling power,water extraction rate and supernatant volume were 0.14%～1.63%,1.18%and 13%～27%lower than that of starch,respectively.Compared with sorghum starch,the peak viscosity,valley viscosity,final viscosity and retrogradation value of the complex decreased by 128 c P,73 c P,96 c P and 23 c P,respectively,and the initial temperature,peak temperature and gelatinization enthalpy of the complex were lower than those of starch.Sorghum polyphenols promoted gelatinization of sorghum starch and delayed the aging of sorghum starch.4.Salicylic acid method,folinol method and 3,5-dinitrosalicylic acid method were used to compare the changes of antioxidant activity,polyphenol release amount and starch digestibility of sorghum starch,polyphenols and their compounds before and during digestion.The results showed that the release amount of polyphenols and antioxidant activity of the complex increased significantly with the extension of digestion time,and the release amount of polyphenols in small intestine was significantly higher than sorghum polyphenols,and the antioxidant activity of the complex was higher than sorghum polyphenols after digestion for 60 min in small intestine.The digestibility of the complex was significantly lower than that of starch,and the contents of resistant starch and slow digestible starch were 9.17%and 6.66%higher than that of starch,respectively.Therefore,the digestive characteristics of sorghum starch and sorghum polyphenols are mutually affected.In conclusion,sorghum polyphenols have certain effects on the structural characteristics,physical and chemical properties and digestive properties of sorghum starch. |
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