Intermittent drying of Lippia origanoides H.B.K. leaves and Schinus terebinthifolius Raddi fruits

Abstract

Drying is an indispensable process for maintaining the quality of medicinal plants after harvest. However, the continuous exposure to heated air during drying can induce physical and physicochemical alteration, besides volatile compounds in the dry plant material. Intermittence has the advantage of reducing the exposure time to heat, introducing tempering periods to drying, minimizing losses due to the process. In this context, the objective of this study was to evaluate the influence of the application of different intermittence ratios on the yield and quality of the essential oil of Lippia origanoides Humboldt, Bonpland, and Kunth (H.B.K.) leaves and of Schinus terebinthifolius Raddi fruits and on the color of Lippia origanoides leaves. The leaves and fruits were subjected to 4 drying procedures: drying without intermittence (continuous drying) and drying with tempering period (10:20; 15:15; 20:10), where the numbers indicate the duration of each interval (drying:tempering), in minutes. The drying air temperatures were 50, 60, and 70 °C and the air flows were 1 m s−1 for the leaves and 2 m s−1 for the fruits. The essential oils of both species were extracted by hydrodistillation and their constituents were identified and quantified by gas chromatography coupled to mass spectrometry (GC–MS). The color of Lippia origanoides leaves was determined by direct reflectance reading of the coordinates L*, a*, and b*, on the adaxial face of the leaves before and after drying. Drying with the 10:20 intermittence ratio at 70 °C provided the highest yields and the best quality of the essential oil of Lippia origanoides dried leaves, preserving Thymol and not resulting in degradation of color attributes. For Schinus terebinthifolius fruits, drying with a 10:20 intermittence ratio at 50 °C maximized essential oil yield and resulted in a higher concentration of the compound α-Phellandrene.