Evaluation of Eight Essential Oils for Postharvest Control of Aspergillus carbonarius in Grapes.

ABSTRACT: A range of fungal species are associated with postharvest spoilage of grapes. However, Aspergillus carbonarius is the primary fungus responsible for the contamination of grapes with ochratoxin A, a mycotoxin causing several confirmed negative health effects in humans and animals. Aiming to find a method, safe for consumers, to prevent postharvest decay and ochratoxin A contamination of grapes, the potential use of essential oils as preservatives was investigated. Essential oils of Origanum dictamnus (dittany), Origanum onites (oregano), Origanum microphyllum (marjoram), Thymbra capitata (thyme), Satureja thymbra (savory), Rosmarinus officinalis (rosemary), Laurus nobilis (laurel), and Salvia officinalis (sage) were tested. The essential oil components were identified by gas chromatography-mass spectrometry analysis. A first evaluation of the effectiveness of essential oils was performed in vitro at a range of concentrations up to 300 µL L-1. Based on the results of the in vitro tests, the four most effective essential oils (O. dictamnus, O. onites, T. capitata, and S. thymbra) were tested on Sultana grapes during postharvest storage. The four essential oils tested, which had carvacrol and/or thymol as a common component, at a high concentration significantly reduced or even inhibited growth of the fungus in all treatments. As revealed from the results, the essential oils of O. dictamnus, O. onites, and S. thymbra were the most effective, causing total inhibition of the growth of the fungus with a minimum concentration of 100 µL L-1, followed by the essential oil of T. capitata, which showed total effectiveness with a minimum concentration of 200 µL L-1. Although essential oils of O. microphyllum, L. nobilis, S. officinalis, and R. officinalis had a significant effect on the growth of A. carbonarius, they failed to inhibit its growth at any of the concentrations tested.

Origanum dictamnus oil vapour suppresses the development of grey mould in eggplant fruit in vitro.

Grey mould rot (Botrytis cinerea) development in vitro or in eggplant (Solanum melongena L.) fruit was evaluated after treatment with dittany (Origanum dictamnus L.) oil (DIT) and storage at 12°C and 95% relative humidity during or following exposure to the volatiles. DIT volatiles used in different concentration (0-50-100-250 µL/L) and times of exposure (up to 120 h) examined the effects on pathogen development as well as fruit quality parameters. In vitro, fungal colony growth was inhibited with the application of DIT oil (during or after exposure) and/or time of application. Continuous exposure to oils reduced conidial germination and production with fungistatic effects observed in 250 µL/L. In vivo, fungal lesion growth and conidial production reduced in DIT-treated fruits. Interesting, in fruits preexposed to volatiles before fungal inoculation, DIT application induced fruit resistance against the pathogen, by reduced lesion growth and conidial production. Conidial viability reduced in >100 µL/L DIT oil. Fruits exposed to essential oil did not affect fruit quality related attributes in general, while skin lightness (L value) increased in 50 and 100 µL/L DIT oil. The results of the current study indicated that dittany volatiles may be considered as an alternative food preservative, eliminating disease spread in the storage/transit atmospheres.