Starch Modification for Slow Release of Herbicide Encapsulated with Concentrated Starch Paste

摘要

An attempt on starch modification has been made to increase the paste concentration of potato starch for reducing the energy consumption required for the encapsulation of herbicide within starch matrix by encapsulating 2, 4-D as model herbicide. The matrix behaviors were evaluated in terms of the herbicide content, capability of swelling in water, encapsulation efficiency, and the rate of herbicide released from the matrix. To increase paste concentration of starch for decreasing the energy consumption in dry process, potato starch was acidified before the encapsulation. However, the matrix prepared in such a way showed that it weakened the control to the herbicide encapsulated, which increased the rate of herbicide released from the matrix. By introducing covalent bonds among starch molecules, the problem with the control and release rate can be completely solved. Moreover, the effects of formaldehyde amount, medium pH, herbicide content, and particle size on the matrix behaviors and release ratewere also investigated. The newly developed matrix shows low capability of swelling and slow release, and reduces water evaporation in dry process by about 40% during matrix preparation.