Effects of selected natural preservatives on the mycelial growth and ochratoxin A production of the food-related moulds Aspergillus westerdijkiae and Penicillium verrucosum

The present study examines the influence of the natural preservatives carvacrol, eugenol, trans-cinnamaldehyde and the essential oil (EO) Origanum vulgare on ochratoxin A (OTA) production and the mycelial growth of two food-related moulds, Penicillium verrucosum and Aspergillus westerdijkiae, by broth macro-dilution assay for 21days. With the addition of 1/2 minimum inhibitory concentration (MIC) carvacrol, eugenol and O. vulgare EO, the mycelial dry weight of both moulds decreased significantly over the whole incubation period of 7, 14 and 21days. Trans-cinnamaldehyde slightly stimulated the growth of A. westerdijkiae and P. verrucosum at 14 and 21days of incubation. Growth inhibition did not accompany inhibition of OTA production. Although the growth of both moulds was inhibited after the addition of 1/2 MIC carvacrol, eugenol and O. vulgare EO, the OTA production of the strong mycotoxin producer A. westerdijkiae was stimulated. Only trans-cinnamaldehyde inhibited the production of OTA with the addition of 1/2 MIC. P. verrucosum produced significantly less OTA than A. westerdijkiae, and its mycotoxin production was almost completely inhibited by the addition of 1/2 MIC of the natural preservatives.