Dependence of coating thickness on viscosity of coating solution applied to fruits and vegetables by dipping method

Hydroxypropyl. methylcellulose solutions were used as coating systems in this study and solution concentrations, viscosity, densities, and surface tensions were characterized. Fuji apples were coated by dipping and stored 4 d at room temperature, after which the internal oxygen and carbon dioxide were measured. Results indicated that coating thickness varied with viscosity, concentration, density, and draining time of the biopolymer solution. Coating thickness relates to the square root of viscosity and the inverse square root of draining time, which agrees with the theoretical approach for flat plate dip-coating in low-capillary-number Newtonian liquids. These results indicate the possibility of controlling coating thickness and internal gas composition based on coating solution properties.