SELECTED PHYSICAL CHARACTERISTICS of GROUND ROASTED COFFEES

The density and compressibility of sieved fractions of ground Colombian and espresso coffees were determined. the magnitude of both depended not only on particle size but also on the roasting and grinding conditions. Compressibility was defined and calculated as the slope of the linear relationship between the logarithm of density and the logarithm of the corresponding compressive stress. Although individual stress relaxation curves of compressed specimens could be linearized, their parameters provided very little useful information, primarily because of the difficulty to control the compact density. Conditioning of these ground coffees with 0.5% calcium silicate had practically no effect on their density and compressibility and only a marginal effect on their color as measured by the Hunter L value.