Effects of different drying techniques on drying characteristics and some quality attributes of sorrel (Rumex Acetosa L.)

Abstract

This research aimed to determine the effect of different drying methods on changes of drying behaviours and some quality parameters (dry matter, colour, water activity) of sorrel (Rumex acetosa L.) leaves. For this purpose, three drying methods were applied for sorrel namely, convective hot air drying using tunnel type dryer, open sun drying and shadow drying. Hot air drying experiments of plants were performed at three drying temperatures that were 40, 50, 60°C and at two air velocities that were adjusted as 1 and 2 m/s. Drying process took 3-17 h in hot air dryer depend on air temperature and air velocity, 50 h in open sun drying and 80 h in shadow drying. The colour parameters for the colour change of the sorrel leaves were quantified using the CIE L?, a?, b? system. The brightness (L?) values of dried sorrels were determined lower than those values of the fresh samples. Redness (a?) values of all dried samples were found higher than those values determined for fresh samples. Yellowness (b?) values decreased for all drying applications. This result shows that the yellow colour tone decreased in the all dried sorrel samples. Water activity (aw) value decreased for all dried samples.