Text Box: 9:30 AM Text Box: Microbiology Text Box: The effect of relative humidity on food powder properties and corona electrostatic coating Text Box: Yichi Xu and Dr. Barringer Text Box: Electrostatic powder coating technology is used to coat food products for more uniform and efficient coating. Relative humidity (RH) is an influential factor for electrostatic charging. The objective of this project is to determine the effect of RH on the food powder physical properties and how this affects transfer efficiency (TE) and adhesion during corona electrostatic coating. 11 food powders, including salts, carbohydrates and proteins, were electrostatically charged by corona electrostatic coating system at 0 kV for nonelectrostatic, ±25 kV for electrostatic coating, at 15-80% RH. Powder flowability, resistivity, TE and adhesion were measured. For salts, improvement in electrostatic TE and powder resistivity decreased with increasing RH. Low powder resistivity causes low charge retention, which lowers TE. For other powders, improvement in electrostatic TE did not change significantly at 20-60% RH, but decreased at 80% RH. For these powders, resistivity is much higher than for salts. These powders can hold enough charge to provide improvement in TE until 80% RH, when powder resistivity decreased and the moist air quenched charge significantly. For adhesion, the higher the powder resistivity, the greater the improvement for electrostatic coating. For proteins, improvement in electrostatic adhesion and powder resistivity were high and decreased with increasing RH. For other powders, improvement in electrostatic adhesion was low and didn’t change significantly with RH. RH of 20-60% didn’t significantly affect the electrostatic coating for most food powders, except for salts, while RH of 80% decreased coating efficiency. 20-60% RH is recommended for corona electrostatic coating.