Investigation of the influence of pre-treatment with ultrasound + ethanol on the drying of mature fruits of Schinus terebinthifolius Raddi

Abstract

The aim of this study was to evaluate the influence of pretreatment (ultrasound + etanol), associated with different drying air temperatures, on the yield and quality of the essential oil of ripe fruits of Schinus terebinthifolius Raddi and to adjust previously described mathematical models in the specialized literature in order to obtain graphical representation of the drying kinetics. The experiments were conducted according to a Central Composite Design considering two factors with the following ranges: pre-treatment duration (ultrasound+ethanol) from 0 to 12 minutes and drying air temperature from 40 to 80 ºC. Four mathematical models, namely: Lewis, Page, Midilli, and Henderson & Pabis, were fitted to the experimental data. The essential oil was extracted by hydrodistillation and its constituents were identified by gas chromatography coupled with mass spectrometry (GC–MS). The Midilli model best represented the drying kinetics of ripe fruits of S. terebinthifolius pretreated with ultrasound + ethanol. The drying time of S. terebinthifolius fruits was influenced both by the pretreatment duration (with linear effect) and by the drying air temperature (linear and quadratic effects). None of the evaluated factors showed significance on the essential oil yield. It was not possible to adjust a model that simultaneously optimized the drying time and the yield of the essential oil of ripe and dried fruits of S. terebinthifolius, previously treated with ultrasound + ethanol.