Dying methods affect the aroma of Origanum majorana L. analyzed by GC-MS and descriptive sensory analysis

Drying is a useful option to extend the shelf life of marjoram (Origanum majorana L.), which is a widely used as herb. The influence of drying method on the quality of marjoram aroma was evaluated. The drying methods tested were: convective drying (CD), vacuum-microwave (VM) drying, and a combination of convective pre-drying and VM finish-drying (VMFD). Marjoram's CD kinetics was described by a logarithmic model, while vacuum-microwave drying kinetics was described by Page model. VMFD drying kinetics followed the model of Henderson and Pabis. Volatile compounds of marjoram samples were extracted by hydrodistillation and analyzed by gas chromatography. Thirty three compounds were tentatively identified and quantified, with cis-sabinene hydrate (229 mg 100 g−1 dry basis, db) and terpinen-4-ol (169 mg 100 g−1 db) being the major components. The total concentration of volatiles of fresh marjoram (825 mg 100 g−1 db) was reduced by most of the drying treatments, except for the treatments VMD at 240 and 360 W. The VMD method at 240 W was the best option for drying marjoram followed by the combined method with 50 °C and 240 or 360 W; the drying times were relatively short (≈162 and 158 min, respectively), and aroma quality was good according to instrumental data (total concentration of volatiles) and sensory evaluation results (high scores of fresh and vegetable odor).