The Study Of Factors Influencing Digestibility And Glycemic Index Of Adzuki Bean Starch And Its Application

Adzuki bean is an important edible bean resource in China with high nutritional value,including plenty of proteins,carbohydrates,vitamins and minerals.The starch of beans is generally considered to have lower digestibility and lower glycemic index(GI)than the starch of cereal and suit for people with diabetes.The influence of different varieties and processing methods on the GI of adzuki bean and its product has not been systematically studied.Therefore,adzuki bean starch and instant adzuki bean powder were taken as the research objects,and the effects of different varieties,gelatinization degree and processing methods on adzuki bean digestibility and glycemic index was main research content.The main results and conclusions are as follows:(1)The starch composition,digestibility and glycemic index(eGI)between different adzuki bean varieties were compared.The results showed that the starch content of 18 varieties of adzuki beans ranged from 40.28 to 46.13%,amylose ranged from 20.74 to 24.96%,and resistant starch ranged from 13.05 to 41.92%.The amylose content and the thermodynamic properties of different varieties of adzuki bean starch was not significantly different,and there is a significant difference in the content of resistant starch(p> 0.05).A comparative analysis of the eGI values of different varieties of adzuki bean starches after cooking was carried out.The results showed that even if there was a significant difference in the resistant starch content,there was no significant difference in eGI after sufficient heating(p> 0.05).No significant correlation was found between starch properties.According to the study,under the premise of sufficient cooking,the impact of adzuki bean varieties on starch digestibility and eGI may not be significant.(2)The effects of different degrees of gelatinization of adzuki bean starch on starch digestibility were investigated.By adjusting different heating intensity,adzuki bean starch samples with different degrees of gelatinization(DG)were prepared,and the digestibility and eGI of starch were measured.The results showed that as DG value increased from 0 to 100,starch digestibility increased from 0.17 to 0.98,and eGI increased from 46.46 to 82.34.The particle morphology of starch molecules is changed from intact state to swell and break state until the particle morphology is completely destroyed,and the ordered structure of starch is also gradually destroyed.The total crystallinity(% C)is reduced from 24.19% to 3.57%.The ratio of absorbance(AR)of 1047 cm-1 / 1022 cm-1 is increased from 0.938 to 0.844 which means the crystalline region turns into an amorphous state.The correlation between structural parameters and eGI shows that DG,AR,% C are highly correlated with eGI(p <0.05),and the relationship between DG and eGI can be expressed by a mathematical model: eGI = 0.2962 × DG + 56.38.It can be concluded that the degree of gelatinization of adzuki bean starch is significantly positively correlated with its eGI value,and the crystal structure of starch is a key influencing factor in controlling starch digestibility.(3)The eGI value of instant red bean powder prepared by different processing methods were compared.The results show that for this instant adzuki bean product,the eGI among different processing methods from low to high is: microwave method(MC,55.00),extrusion method(EC,70.04),cooking method(SC,71.26)and roller processing method(RC,80.05).Further exploration of the internal mechanism was investigated.The degree of starch gelatinization reflected by endothermic enthalpy(ΔH)from low to high is: MC,SC,EC,RC;the degree of integrity of the crystal structure from low to high is: MC,SC,RC,EC,indicating that the two methods of MC and SC maintain more ordered starch structure than RC and EC,which may make starch more difficult to digest and maintain low eGI value.The SC method keeps the bean flour cells in a more complete shape,which provides a more complete physical barrier for starch digestion.Both the EC and RC methods do not maintain an obvious cell structure,but the EC method forms a tightly bonded substance.The contact between starch and enzyme is limited,so the starch digestibility of EC method is lower than RC method.In summary,processing methods of instant adzuki bean powder have a significant effect on the eGI value of the final product,and this may mainly depend on the degree of starch gelatinization and the structural integrity of the granules.