| High amylose corn starch was rich in resistant starch.Experiments have shown that resistant starch(RS)could not only significantly reduced the glycemic index of foods,but long-term consumption could also improved the blood glucose metabolism of diabetic patients and relieved symptoms of the disease.Due to the lack of germplasm resources of high-amylose corn starch,my country's high-amylose corn starch was mainly imported at present,and the cost was relatively high,and there was insufficient research on the basic properties and application of domestic high-amylose corn starch.In this thesis,the self-cultivation high amylose corn starch was extracted,its structure and physical and chemical properties were examined,and the effect of high-temperature heat treatment under the baking process on the properties,structure and digestibility of starch was studied,explored the effect of adding high amylose corn starch on the sensory properties of crisp biscuits,optimized the formula to make low glycemic index biscuits.The main research results of this paper were as follows:(1)The basic components and physical and chemical properties of high amylose corn starch,such as amylose content,moisture content,and particle size,were determined.The amylose content of this starch was 52.93%,which belonged to high amylose corn starch.The moisture content was 13.69%,and the protein and fat content were less,0.26%and 0.76%respectively.Scanning electron microscope observation revealed that the morphology of high amylose corn starch particles was mostly approximately elliptical or round,a few of them were elongated,without obvious edges and corners,the surface of the particles was smoother,accompanied by more milky protrusions,and a small number of particles had surface hole.Polarized light microscope observation found that high amylose corn starch has obvious polarized light cross phenomenon.X-ray diffraction analysis showed that starch had diffraction peaks when the diffraction angle 2?was 17.3°,20.0°,22.0°and 24.0°,which was a typical B-type crystal structure.The analysis and determination by differential scanning calorimetry showed that the initial gelatinization temperature(TO)of starch was 69.14?,the peak gelatinization temperature(TP)was 74.22?,and the end gelatinization temperature(TC)was 86.42?.According to the rapid viscosity analyzer,the high amylose corn starch had obvious gelatinization phenomenon at 95?,the peak viscosity was 212.00 c P,the valley viscosity was 190.24 c P,and the end viscosity was 247.09 c P.The particle size range of high amylose corn starch was 3.55?m-35.33?m measured by laser particle size distribution were analyzer.Measured by GPC-MALLS combined method,the number average molecular weight Mn of the starch was 5.08×107g/mol.The digestibility of high amylose corn starch was measured,and the results showed that the content of fast-digested starch was 21.25%,the content of slow-digested starch was 47.01%,and the content of resistant starch was 31.97%.(2)The high amylose corn starch was subjected to high-temperature heat treatment in a simulated baking process,and the structure,morphology,and physical and chemical properties of the starch after high-temperature heat treatment were measured.After being treated for 0.5,1.0 and 1.5h at 120?,150?and 180?,the natural high amylose corn starch was used as a control.Scanning electron microscopy results showed that the morphology of high amylose corn starch changed greatly after heat treatment,the surface of the particles was not smooth,and there were pits.With the increase of heat treatment temperature and time,the greater the change in the morphology of starch granules.According to X-ray diffraction,after heat treatment,some of the characteristic diffraction peaks of starch were fused,but it was still B-type crystal structure.The crystallinity of starch decreases with the increase of heat treatment temperature and time.Through the analysis of differential scanning calorimetry,the heat treatment reduced the gelatinization temperature and enthalpy value of starch.Under the highest temperature and longest heat treatment conditions,the gelatinization temperature and enthalpy value changed the most.According to the RVA measurement,after heat treatment,the peak viscosity,valley viscosity and final viscosity of starch all showed a downward trend,and the gelatinization temperature was reduced.Through the GPC-MALLS combined method,the molecular weight of high amylose corn starch was reduced after heat treatment.Fourier infrared spectroscopy analysis showed that the characteristic peaks of starch before and after heat treatment did not changed significantly,but with the increase of heat treatment time and temperature,the ratio of A1045/1022decreased,and the crystallinity of starch decreased.The in vitro digestibility of starch was measured,and it was concluded that the content of fast-digestible starch and resistant starch of the heat-treated starch decreased,and the content of slow-digestible starch increased.(3)The formula of low glycemic index crisp biscuits was optimized through single factor and response surface tests.The results were as follows:when the addition amount of high amylose corn starch in the biscuit formula was 40.01%,the addition amount of vegetable oil was 25.15%,the addition amount of maltitol was 24.65%,the addition amount of inulin was 6%,and the addition amount of leavening agent was 0.7%.The sensory score of crispy biscuits was higher,up to 91.08,the blood sugar index was 48.28 according to clinical measurement,which was a low glycemic index food.The prepared biscuits had good appearance,clear surface patterns and crisp taste,which were easy to be accepted by the public. |
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