| The main chemical components and physical-chemical properties of waxy corn starch, normal corn starch and high amylose corn starch with different content of amylose were detected; Scanning electronic microscopy, X-ray diffraction and Diffraction scattering laser particle detection were applied to investigate the surface morphology and granular structure of three kinds of starch; water bath heating, microwave heating and high heating methods were applied to study the effect of three kinds of starch on the pasting properties, at the same time, the application in Cherry Tomatoes coating preservation and the preparation of starch/PVA composite film of three kinds of corn starch was studied.The analysis results showed that the content of amylose of waxy corn starch, normal corn starch and high amylose corn starch were2.34%,33.36%and78.50%, respectively, the transparency, swelling and settling volume of starch paste decreased, freeze-thaw stability and solubility increased as the increase of amylose content. Characterization of granules structure showed that the granule surface of waxy corn starch and normal corn starch was coarse, the particles were polygonal and prismatic, corner was clear:the granule surface of high amylose corn starch was lubricity, ellipse or rotundity; X-ray of waxy corn starch and normal corn starch showed type A, high amylose corn starch showed type B. the degree of crystallinity were26.47%.25.78%and19.59%. respectively.The blue value and enzyme hydrolysability were applied as indicators to study the effect of three kinds of methods on the gelatinization properties of starch, the results showed that the above gelatinization temperature of starch, the blue value and enzyme hydrolysability of gelatinized starch increased as the prolong of heating time and the increase of temperature. Three kinds of starch were gelatinized by microwave and high pressure heating, the effect of high pressure heating on gelatinization of various kinds of starch was better, the rate of gelatinization was faster by microwave heating method, but the degree of gelatinization of the waxy corn starch and normal corn starch was lower than water bath heating and high pressure heating, the degree of gelatinization of high amylose corn starch was lower than waxy corn starch and normal corn starch by water bath heating.The coating preservation liquid were prepared to coat Cherry Tomatoes by impregnation method with waxy corn starch, normal corn starch, high amylose corn starch. The effect of different coatings consisted of starch and glycerol on Cherry Tomatoes were studied. The results showed that weight-loss, decay and the content of soluble solids of Cherry Tomatoes increased, hardness, the contents of total acid and VC decreased, the contents of total sugar first increased and then decreased as the prolong of storage time, and the trend of chance slowed as the increase of amylose content, the results showed that the coating preservation effect of corn starch of high amylose content on Cherry Tomatoes was better.The waxy corn starch, normal corn starch, high amylose corn starch based starch/PVA films were prepared with polyvinyl alcohol, glycerol and borax by casting method, the optimal preparation conditions of starch/PVA composite films were optimized by single factor and orthogonal experiment. The optimum preparation conditions of starch/PVA composite films were obtained:the type of starch was high amylose corn starch, the concentration of starch was7%. the concentration of polyvinyl alcohol was6%. the addition of glycerol and borax was25%and6%. respectively. |
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