Fungal strains isolated from cork stoppers and the formation of 2,4,6-trichloroanisole involved in the cork taint of wine

Cork taint is mainly due to 2,4,6-trichloroanisole (TCA) produced through the activity of undesirable fungal strains. We observed that CFU mould number in TCA-containing stoppers was not quantitatively different to that of the stoppers not containing TCA (ca. 10(5)CFU/g). In contrast more fungi diversity was observed in TCA-containing stoppers. Penicillium spp (Penicillium chrysogenum, Penicillium glabrum), Aspergillus spp (Aspergillus niger and Aspergillus oryzae), Chrysonilia sitophila, Mucor racemosus, Paecilomyces sp. and Trichoderma viride were found in TCA-containing stoppers, while C. sitophila and Penicillium sp. were the main fungi in the stoppers devoid of TCA. Conidia were numerous close to the lenticels and present from the lateral surface through to the centre of the stoppers. Strains of Aspergillus, Mucor, Paecilomyces, Penicillium and Trichoderma isolated from TCA-containing stoppers were able to convert 2,4,6-trichlorophenol (TCP) in TCA in resting cell or growing conditions. The best yields of conversion were obtained by green fungi Paecilomyces sp. and P. chrysogenum, 17% and 20%, respectively. Chysonilia sitophila and Penicillium sp. did not produce TCA from TCP in our conditions.     

The effectiveness of electron beam irradiation to reduce or eliminate mould in cork stoppers

The objective of this research project was to reduce or eliminate moulds known to cause TCA using electron beam (e‐beam) irradiation. Four types of cork were inoculated with Paecilomyces viridis, Penicillium glabrum, Penicillium chrysogenum, Mucor racemosus, Trichoderma viride, Aspergillus oryzae and Cladosporium oxysporum. Cork samples were treated with 5, 10 or 15 kilograys (kGy) of e‐beam irradiation, respectively. Sensory evaluation revealed that irradiation had little or no effect on the overall quality of wine with irradiated corks stored for 56 months. Cork samples viewed under a scanning electron microscope (SEM) showed some structural changes compared to control corks. The results suggest that e‐beam irradiation can significantly reduce or eliminate the moulds known to cause TCA in cork.     

Concentrations of viable airborne fungal spores and trichloroanisole in wine cellars

In wineries, unwanted microorganisms present not only hygienic problems but also have a negative influence on wine quality. An evaluation of Austrian/Styrian wine cellars with regard to the volume and the composition of the mycoflora is very important both for the process of wine production and for occupational safety.Thirty-six wine cellars of 20 vintners were investigated with regard to microorganisms in the air and on material surfaces. Moreover, the presence of trichloroanisole in the air was determined by means of solid-phase micro-extraction. Microorganisms were sampled using the six-stage Andersen-Cascade impactor.The results showed that the concentrations of xerophilic fungi in the air of cellars with large visible mold areas (> 80%) reached values up to 1.4 × 10⁴ colony forming units per m³. In the wine cellars fourteen predominant fungal genera were found in the indoor air, the most frequent was Penicillium. Trichloroanisole was detected in the air of wine cellars with large visible moldy patches. The spore concentrations in the cellar air were two times higher in cellars with Zasmidium cellare growth than in cellars without Z. cellare.These results will serve as a database for further studies.