Study On Preparation And Properties Of Starch-Zn Complex As Nutrient Supplement

Using cassva starch as raw material, starch–Zn complexes were prepared by reaction between zinc acetate and modified starch, which modified by enzyme hydrolysis and heat-moisture treatment. Influencing factors and reaction rules were studied as well, Morphology, granular structure, physical and chemical properties of starch–Zn complexes were also detected, in hope of being treated as new zinc fortifier, and expending the application and research field of starch.As far as hydrosis degree and oil-absorption was concerned, after single-factor experiments and orthogonal test, the optimum conditions of preparing cassava enzymolysis starch were: the amount of enzyme was 1%, the mass radio ofα-amylase to glucoamylase 1:2, the temperatures 55℃, pH value 5.5, hydrolyzing time 16h.After studying the effect of reaction time, temperature, pH value, et al, the optimum conditions of preparing cassava starch-Zn complexes were concluded: reaction pH value 8.0, temperature 40℃, reaction time 24h, concentration of zinc acetate solution is 0.5mol/L. The optimum conditions of preparing cassava microporous starch-Zn complexes were: reaction pH value 8.0, temperature 40℃, reaction time 24h, concentration of zinc acetate solution was 0.5mol/L.The zinc content and its conversion rate of the product prepared were 100.24mg/g,30.84% respectively. The optimum conditions of preparing cassava enzymolysis-heat moisture starch-Zn complexes were: reaction pH value 8.0, temperature 50℃, reaction time 24h, concentration of zinc acetate solution was 0.5mol/L. The zinc content and its conversion rate of the product prepared were 126.38mg/g, 38.89% respectively, which were increased 394% compared with that of cassva starch.Polarized photographs and SEM showed that distinct birefringence were not disappear and product starch granular adhesion together. Significant changes in starch hydroxyl stretching vibration and red shift of absorption peaks of primary alcohol C-O stretching vibration were demonstrated by FTIR spectrum of cassava enzymolysis-heat moisture starch-Zn complexes. Electron binding energy of a kind component in the O1s peak was increased significantly, while electron binding energy of Zn element was reduced, which demonstrated by XPS spectrum of enzymolysis-heat moisture cassava starch-Zn complexes.The solid 13C NMR spectrum of cassava enzymolysis-heat moisture starch-Zn complexes showed that chemical environment of its C6 had been changed, compared with cassava starch, and indicated that interaction between modified starch and zinc acetate were not just adsorption.Therefore, the coordination reaction between zinc acetate and enzymolysis -heat moisture cassava starch was occurred, and Zn was ligand with oxygen of 6-CH2OH by analysis of IR, XPS, 13C NMR spectrums.The physical and chemical properties of starch–Zn complexes were obvious different from that of native cassva starch. Solubility, transmittancy of enzymolysis cassava starch-Zn complexes and enzymolysis-heat moisture cassava starch-Zn complexes increaded, but latter is lower. The conductivity of cassava enzymolysis starch-Zn complexes and enzymolysis-heat moisture cassava starch-Zn complexes were higher than cassva starch, enzymolysis and enzymolysis-heat moisture starch, but lower than the the mixture of zinc acetate with enzymolysis or enzymolysis-heat moisture starch, which also indirectly confirmed that the coordination reaction between zinc acetate and cassava modified starch was occurred, but the reaction was weak.