Study On The Structure And Digestibility Of High Amylose Corn Starch And Cross-linked Starch

Starch is the main energy source of the human body,and its digestibility and nutritional functions have attracted much attention.Resistant starch(RS),while providing consumers with a sense of fullness,can delay postprandial blood sugar rise,control obesity,and prevent chronic diseases such as type II diabetes.High-amylose corn starch(HACS)is a natural RS2type starch with special structure and functional properties;cross-linked starch is a chemically modified RS4 type starch,which can remain granular after high-temperature cooking and has the characteristics of inhibiting enzymatic hydrolysis;the reasons for the resistance to digestion of these two types of starch are not the same.The research on the anti-digestibility mechanism of RS to meet the markets demand for different RS has practical theoretical significance and application value.In this paper,by studying the structural characteristics of the two types of RS,analyzing the granular changes in the digestion process and combining in vivo experiments to clarify the reasons for the resistance to digestion,it will help to further develop foods with resistance to digestion.The main contents of the paper are as follows:Firstly,6 kinds of corn starch with different amylose content were selected as raw materials,and the effect of amylose content and its fine structure on the in vitro digestibility of starch was studied.The study found that the HACS can maintain a complete particle structure after gelatinization and enzymatic hydrolysis,and the gelatinization enthalpy was positively correlated with the RS content.With the increase of amylose content,the content of starch chains with different degrees of polymerization(DP)was different,the content of fa(DP 6-12)decreased,the content of fb2(DP 25-36)and fb3(DP?37)increased,the cluster polymer formed by short chains decreased,and the more hydrogen bonds were formed between long chains,which improved starch thermal stability and resistance to enzymatic.The D value,which characterized the compactness of starch semi-crystalline structure,increased with the increase of RS content.The sample with an amylose content of 61.26 g/100g(referred to HACS 60)had the highest RS content,which had a unique surface fractal structure between 7.41 nm<d(2?/q)<10.58 nm.Secondly,Waxy corn starch(WCS)was selected as raw material,added the cross-linking agent phosphorus oxychloride(POCl₃)and reacted for 3 h under p H 10.5 to prepare cross-linked starch with RS content of 30.01%(referred to as WCS 30%).The study found that the shape of the cross-linked starch granules was not destroyed,the chemical structure did not change significantly,the crystallinity decreased slightly from 16.39%to 14.52%,and the bound phosphorus was distributed on the surface of the starch granules.The RS content of the sample with an amylose content of 51.22 g/100 g(referred to as HACS 50)was 29.35%,which was similar to the RS content of WCS 30%.Both WCS 30%and HACS 50 could keep intact particles after boiling water bath,but WCS 30%particles expanded significantly and the polarized light cross disappeared.After 20 min of in vitro digestion,WCS 30%particles were basically broken,with holes on the surface of the particles;most of HACS 50 particles were intact,and the surface layer was peeled.After 120 min of in vitro digestion,the surface of WCS 30%residual particles was smooth,and the surface of the remaining particles of HACS 50 was rough.These phenomena showed that the digestion resistance of HACS 50mainly came from its ability to keep the particles intact under the action of heat,mechanical and enzymatic hydrolysis;the digestion resistance of WCS 30%was mainly derived from the difficulty of enzymatic hydrolysis of starch chains under the action of cross-linking bonds.Finally,WCS 30%,HACS 50,and HACS 60 with an RS content of 49.10%were added to high-fat feed to study its intervention effects on high-fat diet mice.The results showed that compared with the high-fat group,the weight of the mice in the RS intervention group decreased by 10.1%-16.7%,the fasting blood glucose decreased by 10.2%-18.5%,glucose tolerance and liver function metabolism were improved,Liver weight gain and blood lipid levels were reduced,and the tissue morphology of abdominal fat and liver tended to be normal.The higher the RS content,the better the intervention effect.Comparing the short chain fatty acids in the feces of the WCS 30%sample group and the HACS 50 sample group,it was found that WCS 30%was more conducive to the production of acetic acid and propionic acid,and HACS was more conducive to the production of butyric acid.WCS 30%,HACS 50 and HACS 60 could increase the?-diversity of obese mice and change the composition of intestinal flora.