Effect of Particle Density and Composition on Mixtures During Nonelectrostatic and Electrostatic Powder Coating

Abstract

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.

The influence of particle size on separation and dustiness in powder mixtures during nonelectrostatic and electrostatic coating

“…Fine powders with a higher charge adhere well on the target and increase the adhesion loss of coarse powders by creating a charged layer and repelling the incoming coarse powders [15]. However, in a mixture with similar size powders, using electrostatic coating decreased separation by decreasing targeting loss and adhesion loss of powders in the mixture [6,16].…”

Electrostatic Coating Technologies for Food Processing

“…Data from Sumonsiri & Barringer (2011). different density also cause separation, given that high-density powders are more affected by gravity and have greater adhesion loss than low-density powders (Somboonvechakarn & Barringer 2011). …”

“…Differences in particle size (Somboonvechakarn & Barringer 2009, Wang et al 2005, Ye & Domnick 2003, density (Somboonvechakarn & Barringer 2011, Yousuf & Barringer 2007, and particle surface charge (Yousuf & Barringer 2007) cause separation of the different powders in a food powder mixture during coating. This separation is not desirable in powder coating due to the uneven appearance and distribution of flavors produced on the target.…”

Microencapsulation of oregano (Origanum vulgare L.), rosemary (Rosmarinus officinalis L.) and sage (Salvia officinalis L.) essential oils in β-lactoglobulin

“…Particle density of a dry product is another key parameter since it influences the separation of different particles within a mixture [52]. Particle density is usually determined by a combination of factors such as the solid density, the internal space of the particles and the specific arrangement of particles if applicable [53].…”