Effect of air temperature and velocity on drying kinetics and essential oil composition of Piper umbellatum L. leaves

•Increase in the temperature reduced the drying time in Piper umbellatum L. leaves.•Increased air drying velocity also reduces drying time.•28 substances were found in the Piper umbellatum L. leaves essential oil.•The drying did not influence the substances present in P. umbellatum L. essential oil. Piper umbellatum L. possesses diuretic, antimalarial, vermifuge, and anti-inflammatory properties, in addition to having essential oil in its leaves. Presuming that substances and essential oils in medicinal plants can be altered when they are subjected to various drying conditions, this study aimed to evaluate kinetic drying as well as the composition of essential oil from P. umbellatum L. leaves. The drying process was completed using four temperatures (40 °C, 50 °C, 60 °C, and 70 °C) and two drying air velocities (0.4 and 0.7 m s−1), being the drying process stopped when the moisture content of leaves was equal to 0.11 ± 0.01 dry basis (d.b.). The essential oil of the leaves was determined by hydrodistillation. The chemical components were analyzed by GC–MS. The Midilli model was the only one who represented satisfactorily product drying curves and the rise of temperature and drying air velocity resulted in the increase of the drying rate and in decreasing the content of essential oil from leaves. In total, 28 chemical substances were identified in the essential oil, with piperitone, dillapiole, and myrcene being the majorities. The obtained data indicated that the drying process maintain the quality patterns of the essential oils from the leaves; a slight alteration in the compound percentage was also observed.