Where has all the aroma gone? Identification of aroma compounds in fresh and dried leaves of Melissa officinalis

Melissa officinalis is a popular aromatic plant, renowned for its lemon-like smell and pharmaceutical effects. Drying of Melissa officinalis is important for long-term storage and commercial purposes but can impact the sensory quality of the final product. Here, we aimed to characterize drying-related changes in aroma quality. In a first step, aroma profiles of fresh and dried leaves of Melissa officinalis were established by a trained sensory panel. In a second step, one- and two-dimensional gas chromatography-mass spectrometry/olfactometry (GC-MS/O) was performed to identify odor-active substances from fresh and dried leaves. A hay-like, straw-like and algae-like/fishy off-flavor was evident in dried leaves. GC-MS/O analyses led to the identification of known odor-active substances from Melissa officinalis like neral, geranial, geraniol in both fresh and dried leaves and additionally demonstrated the generation of further odor-active compounds due to drying, amongst others (Z)-4-heptenal and (E,Z)-2,6-nonadienal. Based on these results, further experiments can be designed to further investigate drying-related aroma changes, for instance with regard to quantitative determination of the aroma compounds in the leaves of Melissa officinalis.