Physicochemical Properties And Digestibility Of Buckwheat Starch

We will have satiety for a long time if we take food made of buckwheat flour. As a main component of buckwheat flour, buckwheat starch has a great influence on the digestibility of food whoch is made of buckwheat flour. In this paper, we studied the in vivo and in vitro digestibility of buckwheat starch, buckwheat flour, corn starch and wheat starch. Meanwhile we determined the factors which affect the digestibility of buckwheat starch.First, we determined the basic physicochemical properties of buckwheat starch. Buckwheat starch particle has a rough surface, and the average particle size is about 13.312 u m. The Brabender curve showed that the pasting temperature of buckwheat is 88.8℃. The elastic modulus of buckwheat is much high than its viscous modulus, and the buckwheat paste is close to solid state.Then, we determined the digestibility of buckwheat starch. The Glycemic Index of buckwheat starch is approximately 53.16 as shown by in vivo in people. While the result of in vivo in rat is that wheat starch is digested faster than corn starch, buckwheat starch is digested slower than wheat starch and corn starch, and buckwheat is the slowest. We have the same result by determining the digestibility in vitro.The molecular weight distribution and degree of polymerization of buckwheat starch was determined by high performance liquid chromatography, and the distribution coefficient of buckwheak is 1.41 which indicates a smaller difference between buckwheat starch molecules. The X-ray diffraction showed that buckwheat starch had a typical A-type of crystal structure, and the crystallinity is 40.5%. The amylose content of buckwheat is about 33.22% by dual-wavelength method that was higher than corn starch and wheat starch. The more the amylase is, the lower the digestibility will be.Finally, we analysed the external factor which affect the digestibility of buckwheat starch. We could make a conclusion that the factor was mainly the flavonoids and protein. Different processing also affect the digestibility of buckwheat starch. With the heating temperature increased from 65℃to 85℃, the the maximum hydrolysis rate of buckwheat starch increased; As the buckwheat starch paste stored at 4℃, the more day lasted, the slower it digested. This is because the retrogration occurred in starch paste and the internal re-crystallization hinder the role of the enzyme.