Shrinkage and Mechanical Characteristics of Potato Undergoing Air Convection Drying

Abstract

Using thin discoid and slender cylindrical potato samples, the shrinkage data in all three dimensions were obtained experimentally at a temperature of 60°C, a relative humidity of 5%, and an air velocity of 1.6m/sec. The results are expressed as percentage change of lengths in axis and radius during drying. The relationships between volume and directional shrinkage were discussed. Directional shrinkage was correlated to volumetric shrinkage and moisture removal direction. It was observed that the shrinkage coefficient in the axis was significantly different from that in the radius during air-drying. On the other hand, data describing the mechanical characteristics of cylindrical potato samples were experimentally determined at the above drying conditions. The Young's modulus (E), yield stress (μc), fracture stress (μf) were expressed as a function of bulk moisture content (M). These data for the moisture ranges used in conventional potato drying can help to optimize the drying conditions and the drier design. © 2001, Japan Society for Food Engineering. All rights reserved.