| Natural starch is a good texture stabilizer and regulator in food system,but it has many limitations such as low shear resistance,low heat resistance,high thermal decomposition and high degradation trend,which affect its application and promotion in industrial food.Among them,waxy com starch made from waxy maize(waxy corn)contains more than 95%amylopectin.In this study,chemical modified starch with different degree of substitution and different functional properties was prepared by combining debranching technology with esterification technology.Firstly,pullulanase was applied to waxy corn starch and the debranched waxy corn starch were obtained by slowly enzymatic hydrolysis of amylopectin through exaction,which was used as the experimental material of this subject.Then,on the basis of previous research of our group,the esterification method was further improved with different raw materials,and the unique physicochemical properties of modified starch were deeply explored.Citric esterified and acetic esterified debranched waxy corn starch was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,thermogravimetric analysis,in vitro digestion,X-ray diffraction,differential scanning calorimetry,laser particle size analysis and optical microrheology.The research results are as follows:1.Esterification reaction of citric anhydride with enzymatic debranched waxy corn starch was controlled by adjusting pH to obtain citric acid esterified debranched waxy corn starch.It was found that when the mass ratio of citric anhydride to enzymatic debranched waxy corn starch was 2:5 and the esterification temperature was 150 C?the degree of substitution was 0.483.The appearance of the particles is in the state of accumulation of tiny spherical crystals,and the surface is slightly rough,and a small part of the particles stick together.In vitro digestion experiment,citric esterified starch showed strong digestive resistance and stable performance.Its X-ray diffraction results indicate that its crystal structure is type A,crystallinity was increased,and thernal stability was decreased and enthalpy change energy was reduced.It is insoluble in boiling water and its particle size was increased with an average particle size of 244.40 ?m.2.Esterification reaction between acetic anhydride and enzymatic debranched waxy corn starch was controlled by dripping iodine as catalyst and adding sodium chloride solution to obtain acetate-esterified debranched waxy corn starch.It was found that the white transparent colloid was obtained by adding anhydrous ethanol at the volume ratio of 1:1 after esterification with acetic acid,and its degree of substitution was 0.286.The morphology of the granules is that there are uneven holes on the surface,and the holes only appear on the surface of acetate-esterified debranched waxy corn starch,but do not enter its interior.In the in vitro digestion experiment,the acetate debranched starch also has obvious anti-digestion ability.The characteristic diffraction peaks of starch in the X ray wide-angle map tended to be gentle and the crystallization peaks disappeared,but the characteristic absorption peaks of iodine appeared at about 21 degrees and sodium chloride appeared at 32 degrees.At the same time,its thermal stability was decreased,and enthalpy change energy was decreased,and only a small amount of samples was dissolved in boiling water.Most of them are light yellow flocculent or granular precipitation.The particle size of acetic acid esterified dewaxy waxy corn starch was decreased significantly with an average particle size of 22.85 ?m.The experimental products were mainly liquid and showed strong viscosity.The solid-liquid equilibrium point is 0.68 and the viscosity is 170100 CP. |
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