Influence of postharvest storage conditions on physiological responses, bioactive compounds, and antibacterial activity of fresh thyme (Thymus vulgaris)

Great interest is given nowadays to preserving the quality and prolonging the shelf life of herbs marketed as fresh. Storage of these products under non-optimum conditions could result in high perishability. The current work investigated the impact of storage temperature (2, 6 and 20 °C) and relative humidity (RH) (high-95% and atmospheric-65%) on the quality attributes of fresh thyme during its postharvest storage and the proposal of the optimum storage conditions for this herb. Based on the results, elevated weight loss and respiration rate were observed during storage of fresh thyme at room temperature (20 °C) compared to lower temperatures. On the other hand, thyme stored at 6 °C exhibited higher phenolic content and antioxidant activity. Regarding the impact of RH levels during the postharvest storage of fresh thyme at 6 °C (optimum temperature selected), no significant changes in most of the investigated quality attributes were reported between the investigated RH levels, while the essential oil (EO) yield obtained from thyme stored under high RH was significantly higher than the one obtained from plants exposed to atmospheric RH. The antibacterial activity of the infusions from thyme stored under 6 °C were found to be slightly lower compared to other temperatures when tested against Escherichia coli, while Listeria monocytogenes was more susceptible. From these findings it can be concluded that storage of fresh thyme at 6 °C with high RH (95%) could be considered optimum for this herb.