The combination of alginate coating and essential oils delayed postharvest ripening and increased the antioxidant potential of two sweet cherries

Sweet cherry (Prunus avium L. 'Sonata' and 'Sweetheart') fruits were harvested at commercial ripening and transferred immediately to the laboratory. Fruits were selected for the following treatment: a) control (distilled water); b) alginate at 3%; and c) alginate at 3% plus a mixture of essential oils (thymol, carvacrol and eugenol at 25 µL each 100 mL^-1). All treatments were performed by dipping the fruit in the corresponding solution for 2 min and then stored for 16 days at 2°C. Samples were taken out from chamber every 4 days and left 2 days at 20°C for analytical determinations. Results showed that parameters related to postharvest ripening, such as colour and firmness were significantly delayed in 'Sonata' and 'Sweetheart' coated cherries, as well as respiration rate and weight loss. Interestingly, the addition of the essential oils led to greater delays on the above parameters for both cultivars. The analysis on the evolution of bioactive compounds with antioxidant activity, such as total phenolics and anthocyanins, revealed that concentrations were significantly higher in treated than in control cherries. The incorporation of the essential oils led to higher values of total antioxidant activity in the lipophilic fraction, while did not affect the hydrophilic fraction. Finally, no occurrence on fruit decay was observed for any treatment. In conclusion, the combination of alginate coating with essential oils is considered as a good postharvest tool to increase the shelf life of sweet cherry cultivars with beneficial effects in terms of increasing the antioxidant potential.