Studies On Process Optimization And Properties Of Phosphorylated Chestnut Starch

Phosphorylated chestnut starch was produced by a semi-dry process, in which chestnut starch, and sodium dihydrogen phosphate were used as a raw material, and an esterifying agent, respectively. Its technological conditions and physicochemical properties were investigated. The product hopefully became phosphorylated chestnut starch in different degree of substitution (DS).Single-factor test and response surface analysis were performed in this study. Using design-erpert8.0Box-Behnken design and response surface analysis method to study on the major factors:sodium dihydrogen phosphate (A)、 reaction temperature (B)、reaction time (C) and pH (D) which influenced on apparent viscosity of phosphorylated chestnut starch.The results showed that: The optimum preparation conditions were listed as follows:NaH2PO4concentration of7%; reaction temperature of146℃; reaction time of140min; and pH6. The average experimental apparent viscosity under the optimum conditions was found to be33.69Pa-s, with an increase of208.99%higher than that of native chestnut starch. On the basis of the optimal process, phosphorylated chestnut starch in different DS were prepared by changing the reaction time.Fourier transform infrared spectrum (FTIR) analysis revealed that some of hydroxyl groups were replaced by phosphate groups during phosphorylation. Scanning electron microscopy (SEM) showed that native chestnut starch granules exhibited a smooth surface with complex and varied shapes (usually circular, oval, triangle, pear-shaped, or irregular) but without edges or cracks. The phosphorylated starch granules lost their smoothness and structural integrity, and exhibited different levels of indentation, damage, and fracture. X-ray diffraction (XRD) analysis indicated that the crystalline type of chestnut starch and phosphorylated chestnut starch was type C. The crystalline region of phosphorylated chestnut starch was slightly damaged, and the slight variation in the crystallization area was insufficient to change the crystalline shape. Therefore, the modified esterification did not change the crystalline type of chestnut starch.Study on physicochemical properties of phosphorylated chestnut starch in different DS. The results were as follows:the transparency, solubility, force of expansion, freeze-thaw stability of phosphorylated chestnut starch in different DS were improved significantly compared with original chestnut starch. The gelatinization temperature of the phosphorylated chestnut starch was less than that of chestnut starch, with the increase in the DS, the gelatinization temperature of the phosphorylated chestnut starch was reduced and the values of peak viscosity, minimum viscosity and final viscosity were increased. Texture profile analysis (TPA) indicated that with the increase in the DS, the hardness, frangibility, gumminess and chewiness of phosphorylated chestnut starch reduced, and the cohesion and adhesion of the increase with the DS were increased. Observed by differential scanning calorimetry (DSC), after esterification of starch, the pasting temperature decreased and the pasting enthalpy got lower and the range of pasting temperature got narrow. Rheological analysis shows that with the increase of shear rate, the apparent viscosity of phosphorylated chestnut starch decreased rapidly with the character of pseudoplastic fluid. with the increase in the DS, the apparent viscosity of phosphorylated chestnut starch were increased under the same shear rate.