Impact of essential oils on growth and ochratoxin A production by Penicillium verrucosum and Aspergillus ochraceus on a wheat-based substrate.

Abstract

An in vitro initial screen of twenty-four essential oils for inhibition of spore germination and mycelial growth of mycotoxigenic strains of Penicillium verrucosum and Aspergillus ochraceus was made at 25°C and 0.99 water activity (aw). Based on a measurement of clearing zones, six essential oils were found to be effective in inhibiting growth: bay leaf (west Indian), cinnamon leaf, clove bud, clove leaf (cleaned), lemongrass and thyme. Based on those giving clearing zones greater than 5 mm, three were chosen for a more detailed study (clove leaf, cinnamon and bay leaf). The detailed screen was at 0-500 ppm on a 2% milled wheat agar modified to 0.99-0.90 aw for 56 days at 15°C and 25°C for isolates of both species. Generally, growth of the A. ochraceus and P. verrucosum was slower at 15°C than 25°C. Generally, regardless of temperature or aw there was significant (>90%) inhibition of growth with 500 ppm of these essential oils. However, at suboptimal concentrations, especially 50 ppm, some essential oils stimulated growth of both A. ochraceus and P. verrucosum by up to 10-15%. Analysis of the impact on ochratoxin A (OTA) production supported these findings. At 50 ppm there was stimulation of OTA production regardless of aw or temperature. However, at 500 ppm significant control of OTA production by A. ochraceus was observed with the best essential oil treatments. OTA production by P. verrucosum was completely inhibited at the maximum concentration and under the environmental conditions used.

Insecticidal activity of synthetic antioxidants, natural phytochemicals, and essential oils against an Aspergillus section Flavi vector (Oryzaephilus surinamensis L.) in microcosm

“…The effects of essential oil of clove and its principal components eugenol, on growth and mycotoxin production by some toxigenic fungal genera like Aspergillus spp., Penicillium spp., and Fusarium spp. had been reported previously (Cairns and Magan 2003, Hope et al 2003, Velluti et al 2003, 2004. This component was able to inhibit both growth and/or mycotoxin production (Bluma and Etcheverry 2008).…”

Radiant heat treatments for corn drying and decontamination

“…Chemical residue from fumigants are sometimes found in food and could pose a great danger to the consumer. Cairns et al () observed that issues of poor coverage of the grain often lead to growth of spoilage fungi, especially mycotoxigenic molds; these mold may in fact, metabolize applied chemicals.…”

Control ofAspergillussectionFlavigrowth and aflatoxin accumulation by plant essential oils

“…Growth rate stimulation was observed in some cases when Aspergillus section Flavi grew with the lowest concentration of peperina and peppermint essential oils; however, this stimulation did not occur in all aflatoxigenic isolates. The stimulation on growth rate and mycotoxin production by suboptimal concentration of different essential oils was observed by Cairns and Magan (2002) and Hope et al (2002). Under these conditions, active growth is likely to occur and the imposition of stress could result in a survival or defence response by enhanced mycotoxin production .…”