Changes of essential oil content and composition during convective drying of lemon balm (Melissa officinalis L.). Industrial Crops and Products
- Publication Type
- Journal contribution (peer reviewed)
- Authors
- Argyropoulos, D; Müller, J
- Year of publication
- 2014
- Published in
- Industrial Crops and Products
- Band/Volume
- 52/
- DOI
- 10.1016/j.indcrop.2013.10.020
- Page (from - to)
- 118-224
tThe impact of hot-air drying on essential oil content and composition of lemon balm leaves (Melissa offi-cinalis L.) was investigated at different temperatures within the range of 30 and 90◦C, constant specifichumidity of 10 g kg−1dry air and uniform air flow of 0.2 m s−1. Essential-oil reduction was determined byhydrodistillation of samples during drying and the experimental data was fitted to a first-order reactionkinetics model. The dependence of temperature on the rate constant was expressed by the Arrhenius-typerelationship. The volatile compounds of the essential oil were analyzed by GC/FID. The multifunctionalsurface structures of leaves were also viewed by a scanning electron microscope. In all cases, most of theoil loss was observed at the beginning of the drying process and it was proportional to drying tempera-ture. Convective drying of leaves at 30 and 45◦C resulted in 16% and 23% loss in essential oil respectively,whereas drying at higher temperatures caused significant essential oil losses, for instance 65% at 60◦C.Pronounced changes in the major essential oil components occurred at 60◦C: neral, geranial and citro-nellal were decreased, while citronellol indicated an increasing tendency. Micrographs showed that theoil glands are sparsely distributed on the lower epidermis of the leaf. Apart from the temperature sensi-tivity of the oil constituents, the loss of essential oil can also be attributed to the structural modificationscaused by drying.