Two mixtures, 44 and 256 mm NaCl and 64 and 191 mm starch, were nonelectrostatically or electrostatically coated onto an aluminum target. The coating processes cause the proportion of each powder in the mixture to be different on the target than in the initial mixture. First, some loss of powder occurs during the targeting step; thus, not all of the powder land on the target. This targeting loss is caused by the individual powder characteristics and interactions that occur between powders in the mixture. Also, an uneven distribution is produced on the target due to the way the powder is dispersed. Finally, adhesion loss occurs on the target, also due to individual and mixture characteristics. During nonelectrostatic coating, the largest cause of the change in proportion was targeting losses. During electrostatic coating, the largest cause was adhesion loss. Interactions in the mixture decreased the change in proportion, except for nonelectrostatically coated NaCl. PRACTICAL APPLICATIONSFood coatings consist of mixtures of powders of different sizes. It is desirable to maintain the same proportions of the powder components on each food sample as in the applied coating. Mixtures change proportions due to differences in particle size, so all of the powders in the mixture should have a similar size range to reduce changes during coating. During nonelectrostatic coating, the differences in targeting losses are the biggest cause of this change, so coating systems need to be designed to minimize the differences in targeting losses. Electrostatic coating reduced targeting loss by a large amount; therefore, it is one method to reduce the change in proportions caused by targeting 1 Corresponding

Nonelectrostatic and electrostatic coating processes cause the proportion of each powder in a mixture to be different on the target than in the initial mixture. First, some loss of powder occurs during the targeting step; thus, not all of the powder lands on the target. This targeting loss is caused by the individual powder characteristics and interactions that occur between powders in the mixture. Also, an uneven distribution is produced on the target because of the way the powder is dispersed. Finally, adhesion loss occurs on the target, also because of individual and mixture characteristics. During nonelectrostatic coating, a mixture of fine NaCl and starch particles changed in proportion due to the differences between individual targeting, and mixture adhesion, losses. Little change in proportion occurred in the coarse NaCl and starch mixture. During electrostatic coating of both mixtures, proportions changed because of differences between individual adhesion losses. PRACTICAL APPLICATIONS Food coatings usually consist of mixtures of powders with different densities and compositions, which cause separation of the powders. For maximum consumer acceptance, the powder should be evenly coated on the surface, with the same proportion of ingredients as in the original powder. In fine powder mixtures, during nonelectrostatic coating, targeting loss is the biggest cause of separation. Therefore, when mixtures of different density and composition are used, the coating systems need to be designed to minimize the targeting loss difference between the powders. Electrostatic coating reduced targeting loss of the fine powders by a large amount; therefore, it is one way to decrease separation. Electrostatic coating of both mixtures had high adhesion loss; therefore, the electrostatic coating system needs to be designed to minimize adhesion loss, such as by addition of oil or other tack agents, when powder mixtures are coated.

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