EFFECT OF PARTICLE DENSITY AND COMPOSITION ON MIXTURES DURING NONELECTROSTATIC AND ELECTROSTATIC POWDER COATING
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.
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.
Document Type: Research Article
Affiliations: Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Road, Columbus, OH 43210
Publication date: 2012-04-01