Ochratoxin A removal during alcoholic fermentation

OCHRATOXIN A REMOVAL DURING ALCOHOLIC FERMENTATION

Department of Agro-Forestry and Environmental Sciences and Technologies, Mediterranea University of Reggio Calabria, Gallina, Italy.

A. TAFURI, A. RITIENI

Department of Food Science, Federico II University of Napoli, Portici, Italy.

Ochratoxin A (OTA) is a dangerous secondary metabolite; this mycotoxin frequently occurs in various foods and beverages and is bio-produced by a few species belonging to the Aspergillus and Penicillium genera. Since 1996, OTA has been reported in grapes, grape juices and wines [1]. In alcoholic beverages, OTA is formed prior to alcoholic fermentation, during which, however, it is partially removed or degraded [2]. Interestingly, this decrease in OTA is strain-dependent [3]. Different decontamination procedures using Saccharomyces strains were recently proposed for OTA removal [4-6], but no study has been carried out to select starter yeasts able to remove OTA during alcoholic fermentation.

This work aims to investigate the performance of twenty strains of Saccharomyces sensu stricto, previously selected for winemaking and studied in vitro for OTA removing capacity [6], to remove OTA during alcoholic fermentation. Each strain of Saccharomyces was inoculated in triplicate in test tubes containing 10 mL of must obtained from Calabrian white grapes naturally contaminated with OTA (1.58 ng/mL), and again in triplicate using the same must artificially contaminated with OTA (7.63 ng of OTA/mL) contaminated. This microvinification trial was performed at 25°C for 90 days and then wines and lees were analysed. The toxin content and the ethanol content of the wines were assayed; the toxin content of the lees was also analysed separately. The OTA content in wines produced from the naturally contaminated must varies from 0.143 to 0.950 ng of OTA/mL (mean 0.498 ng of OTA/mL). The OTA content in wines obtained from the artificially contaminated must varies from 1.270 to 2.448 ng of OTA/mL (mean 1.661 ng of OTA/mL). The OTA content in lees varies from 1.537 to 7.456 ng of OTA/mg of biomass (wet weight). These last extremely interesting results indicate that OTA-removal from grape must was probably carried out by the yeast cell wall, acting like a sponge.

A role of the parietal yeast mannoproteins in OTA adsorption was hypothesised. The potential implications of these results in the control of the alcoholic fermentation of OTA-contaminated musts were discussed.

Acknowledgements

We thank Dr. Santo Postorino for its help with the ethanol analyses.

References

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