Influence of Enological Practices on Ochratoxin A Concentration in Wine

Abstract

The effects of several enological practices on ochratoxin A (OTA) concentration in wines were evaluated. Analysis of OTA was performed by reverse-phase high-performance liquid chromatography (HPLC) after immunoaffinity cleanup. Higher toxin levels were found in red wines (0.017 to 0.050 μg/L) than white wines (0.006 to 0.022 μg/L). Intensive pressing of pomace, prolonged drying of grapes, and storage in partially empty tanks increased OTA contamination of wines. Poor winery sanitation practice was the primary source of OTA contamination, as wines from contaminated wineries had the highest OTA values (0.130 to 1.300 μg/L). Filtration through a 10-μm membrane and heating on hot plates at 55°C did not cause a significant decrease in the toxin level. An 80% decrease of OTA was observed after wine filtration through a 0.45-μm membrane (p < 0.05). Eleven enological fining agents were tested to study their ability to remove OTA from wine. Enological decolorizing carbon removed (at 30 g/hL) up to 72% of OTA. The Freundlich isotherm was used to model OTA adsorption on carbon. Results showed that carbon had selective adsorption (K_F = 3.172 (mg/g)/(mg/L)^0.8474), but it did not affect polyphenol content and color of red wine. Nevertheless, a decrease of key sensory odorants of wine, such as 3-methylbutyl acetate, ethyl hexanoate, ethyl octanoate, and geraniol, was observed.