Modification of the Hydrophobicity of Different Starches and Their Properties
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Abstract:
Various properties including the angle of repose, activation index, contact angle, dispersibility, and polarized light property of different types of starch (corn starch, tapioca starch, and potato starch) were analyzed in this study. Additionally, the effects of different pH conditions and different concentrations of added octenyl succinic anhydride (OSA) and Al3+ were investigated. The results showed that the angles of repose of corn and tapioca starch presented an initial decrease, followed by an increase, with higher pH values and increasing concentrations of added OSA and Al3+. Variation of pH value showed an obvious effect on angle of repose in case of potato starch only. Modification caused the contact angles of different types of starch to increase to >90°, indicating a significant improvement in the hydrophobic property of all three kinds of starch. The activation index for both, tapioca and potato starch reached a value of 0.95. The results of the dispersibility test in liquid paraffin showed highest dispersibility for corn starch, followed by tapioca starch, whereas potato starch showed lowest dispersibility. However, the dispersibility of modified starch did not change significantly as compared to that of native starch. Finally, the properties of starch under polarized light of the same intensity showed that the birefringence of modified starch granules was weaker and the shadow areas were larger.
