Cereal Chem 68:262-266   |  VIEW ARTICLE

Encapsulation of Atrazine Within a Starch Matrix by Extrusion Processing.

M. E. Carr, R. E. Wing, and W. M. Doane. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

Atrazine, a powdered herbicide widely used in agriculture, was encapsulated within a starch matrix by a continuous process in a twin-screw extruder under various conditions. Four extrusion procedures were evaluated. Unmodified cornstarch was gelatinized in the extruder in the presence of the herbicide and water (starch concentrations in the water were 20-65%); atrazine was added at levels of 5-20% (product basis). The extruded materials were cooled, dried, ground, and sieved to obtain granular products of 10-20 and 20- 40 mesh. These products were analyzed for encapsulation efficiency, swellability in water, and release of active agent in aqueous ethanol (10%). Effects of extrusion, milling, and drying variables on properties of encapsulated products were studied. This work suggests that excellent potential exists for producing starch- encapsulated products with a range of customized release properties by applying twin-screw extruder technology. The production rate of the starch-encapsulated herbicide containing 10% atrazine was scaled up from 12 lb/hr (db) in a ZSK 30 to 167 lb/hr in a ZSK 57 twin-screw extruder. An encapsulation-efficiency value of about 90% was achieved at both production rates. The starch-encapsulated atrazine, prepared in the ZSK 57, will be evaluated in field trials in seven states