The Determination of Moisture in Parchment Coffee and Green Coffee Beans with a Dielectric-type Moisture-Meter

Abstract

1. It is necessary for all those concerned with the production, processing, and handling of seedlike products such as coffee parchment and green coffee to have available a method for the rapid and simple determination of moisture content. 2. A review of the literature indicates that much work has been done on the moisture determination of the seed of commerce of the Temperate regions, but little information exists concerned with the moisture determination of coffee. 3. As an initial step in setting up a program to investigate methods of coffee-processing it was necessary to establish a quick, simple, and accurate method of moisture determination. Investigations by others indicated that the Kappa moisture-meter, manufactured by Messrs. Kappa Moisture Meter Ltd., U. K., was probably the most suitable instrument available for this purpose. 4. It was decided to use a distillation method as the primary means of establishing the relationship between the moisture content of the material and the meter reading. It was found that it was not only necessary to determine the meter reading but also the weight of the sample and the ambient temperature if reliable results were to be obtained. 5. The Kappa moisture-meter was calibrated both for coffee parchment and green coffee over the widest possible range of moisture contents likely ever to be encountered. 6. All the results were statistically evaluated. It was found that, if the weight of the sample and the ambient temperature were taken into consideration, the standard deviation from the regression or the standard error of estimate for both parchment and green coffee were very comparable to similar values obtained for other dielectric moisture-meters used for moisture determination in wheat over a much more limited range. 7. It was found that the range of the Kappa moisture-meter was sufficient for the entire range of moisture contents considered. The divisions on the meter scale were also found to be adequately spaced, so that all readings could be made with sufficient accuracy. 8. It was observed that there was a very close relationship between the weight of a given volume of moderately compacted coffee parchment and its moisture content. This relationship could perhaps form the basis of a cheap, simple way for roughly evaluating the moisture content of parchment coffee which would be sufficiently accurate for farm use. 9. It was considered that the most convenient method of determining the moisture content from the Kappa meter-reading, the sample weight, and the ambient temperature, is by means of a four-variable addition-type alignment chart or nomogram. 10. Though the linear regression equations established for Kappa moisture- meter, Serial No. 7755, are unlikely to be applicable to other moisturemeters of the same type, additional meters required can be calibrated from this original meter instead of by more tedious primary methods.