Only slight differences in lightness (Fig. 2a) were observed among the different samples. By contrast, the decrease in hue angle (Fig. 2b) was greater in the vacuum-processed coffee up to an F value of approximately 3.8 min. At increasing F values, browning was significantly higher for the conventionally roasted coffee. Nevertheless, these differences in hue angle were almost not appreciable by visual observation of the medium and dark roasted ground samples (Table 2).