Effect Of Hydrocolloids With Heat-moisture Treatment On The Digestibility Of Corn Starch

With the rapid development of economy and the improvement of living standard,people's dietary requirements tend to be more nutritional and healthier.Starch has a wide range of sources and is the main energy source of human beings,and its digestibility is closely related to nutritional value and human health.Modifications of starch delay its digestion and absorption in the body,and can prevent and control obesity,type II diabetes and other chronic diseases.The heat-moisture treatment(HMT)and the addition of hydrocolloids,as common physical modification methods,have the potential to reduce the digestibility of starch to a certain extent,and are more environmentally friendly than chemical and biological modification.Therefore,in this paper,normal corn starch(CS)and three types of hydrocolloids(Gum Arabic,GA;Xanthan gum,XG;Guar gum,GG)were used as materials to explore the effect of HMT on the digestibility of starch and starch-hydrocolloid complexes.Additionally,the regulating effect on lipid metabolism of starch and complexes with HMT was confirmed by animal experiments to verify the effect of HMT on reducing digestibility of starch and complexes.The main research contents of this paper are as follows:Firstly,the effect of HMT on the digestibility of starch and complexes was investigated.Through single factor experiments,it was determined that the CS showed the lowest rate of digestion under the conditions of moisture content was 20 g/100 g,temperature was 120°C and reaction time was 4 h.The temperature and moisture content of HMT affected the unwinding and movement of starch chains,and the reaction time of HMT affected the degree of starch chains' rearrangement.The three factors affected the consequence of HMT together,which in turn affected digestibility.The results of this study showed that the digestibility of the starchhydrocolloid complexes was significantly reduced after HMT.Among them,the resistant starch content of CS-GG complex prepared at a ratio of 1:40 with HMT was up to 43.99%,which was 28.63% more than the complex without HMT.Moreover,the reduction ratio(25.59%-32.01%)of the digestibility of complexes was more than that of normal corn starch(15.54%),indicating that the effect of HMT on the interaction between corn starch and hydrocolloids could further affect the digestibility.Secondly,the reasons for the influence of HMT on the digestibility of starch and complexes were studied.The results of particle size distribution and particle morphology showed that after HMT,the hydrocolloid covered the surface of starch granules more uniformly.The starch granules adhered and aggregated under the effect of XG or GG to form large particles of about 100 ?m,which hindered the contact between digestive enzymes and starch granules.X-ray diffraction patterns showed that HMT didn't change the crystal form,but the relative crystallinity showed a downward trend.The relative crystallinity of the complexes showed a greater reduction than corn starch,with a maximum reduction of 16.11%.The double helix structure in the crystalline region was destroyed and partially rearranged into a denser crystalline structure.After HMT,the paste temperature of was delayed.The gelatinization enthalpy,breakdown,and setback were significantly reduced,indicating that the thermal stability and anti-enzymatic ability was enhanced after HMT.After HMT,the mobility of water molecules decreased,which in turn limited the movement of digestive enzymes.These factors led to the changes of digestibility of the normal corn starch and complexes after HMT.Finally,CS and starch-hydrocolloid complexes prepared at a ratio of 1:40,with high resistant starch content,were used to intervene high-fat diet mice to explore its role in regulating lipid metabolism in vivo.Compared with the high-fat group,the body weight,liver weight and fat index of the mice in the intervention group were significantly reduced.The glucose tolerance was improved,and the blood lipids level and liver function metabolism level tended to be normal.The liver and adipose tissue morphology returned to normal.Among them,the interfering effect of CS-XG complex prepared at a ratio of 1:40 with HMT was the best.By measuring the mRNA expression levels of genes related to liver lipid metabolism,it was found that the intervention of corn starch and complexes after HMT could down-regulate the expression level of genes related to fat synthesis(FAS,ACC-1,SREBP-1c),compared with the high-fat group,thereby decreasing lipid deposition and stabilizing the blood lipid levels.