The development of mathematical models capable of relating the relative permittivity epsilon' and the loss factor epsilon" of seeds to their moisture content is a fundamental step towards designing seed moisture meters for on-line operations in automatic control processes such as seed harvest, drying and aeration. The object of this research is the assessment of three dielectric models that would allow the density-independent determination of the moisture content of moving seeds of parchment coffee. Seed samples of varieties Catuaí Amarelo, Catuaí Vermelho and Mundo Novo with moisture contents in the range from 11 to 23% w.b., and bulk density ranging from 326 to 455 kg.m-3 have been used. In terms of instrumentation accuracy the best bulk-density dielectric model for coffee seeds moisture content estimation was the one which employed both epsilon' and epsilon" measured at 0.5 and 5.0 MHz as indicators of the amount of water present in the seed samples. The standard errors of calibration and prediction were 1.3 and 1.2 percentage points moisture, respectively.
Coffea arabica; moisture content; dielectric properties; instrumentation
