The effect of drying sweet basil in an indirect solar dryer integrated with phase change material on essential oil valuable components

Abstract

In the present work, the quality of sweet basil leaves volatile oil dried by indirect mode forced convection solar dryer (IMFCSD) integrated with thermal storage material was investigated and compared with the traditional air-drying method. It is found that the indirect solar dryer is capable of drying the basil leaves for 31 h (including the night hours) when the phase change material was used, while it is required 60 h to dry the basil leaves in natural air. In order to ensure that the proposed solar drying method preserves the basil valuable components, an untargeted gas chromatography-mass spectrometry (GC/MS)-based metabolomic technique was used to investigate the impact of the indirect solar drying process on the Volatile organic compounds (VOCs) profile of the basil essential oil. GC/MS analysis revealed that 62 different VOCs were detected in either natural-air dried, indirect solar-dried samples or both together. The usage of indirect solar dryer resulted in higher abundances of 31 detected VOCs. There was no significant difference in the abundance of methyl eugenol, however, there were significant differences in the abundance of most minor components for the favor of IMFCSD. Collectively, these findings indicate that the IMFCSD is much better than natural air drying which might be referred to the controlled drying environment and the stability of drying temperature.