Ochratoxigenic Aspergillus species on grapes from Chilean vineyards and Aspergillus threshold levels on grapes
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Date
2009
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Abstract
This study reports the incidence of ochratoxigenic strains of Aspergillus on Chilean grapes (Vitis vinifera) and wineries, and production of OTA levels in wines with grapes having different levels of contamination with OTA-producing Aspergillus carbonarius was studied. A. carbonarius, A. niger, A. niveus, A. paradoxus, A. versicolor, A. wentii, and A. westerdijkiae were identified on apparently healthy clusters of red and white grape cultivars. However, A. carbonarius and A. niger were the most frequently identified species, mow abundant on red than white grape cultivars. Aspergillus spp. populations increased between veraison and harvest, but the isolation frequencies were relatively low over the entire growing season. At the winery, A. carbonarius, A. niger and A. westerdijkiae were occasionally found in the air, exclusively during winemaking. OTA-producing strains were only found among isolates of A. carbonarius, A. niger, A. wenti, and A. westerdijkiae. producing 2 to 17 mu g/L of OTA in liquid medium; however, A. westerdijkiae produced the highest OTA concentration in vitro. Red wines elaborated with 0.5% of grapes infected with an OTA-producing strain of A. carbonarius (Aspuc-SB36) exceeded the 2 mu g/L of OTA tolerance established for wines by the European Community. Therefore, a threshold below 0.5% infected berries is proposed for red wines. ELISA tests proved to be useful for detecting OTA in broth culture as in wine samples. (C) 2009 Elsevier B.V. All rights reserved.
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Keywords
Ochratoxin A, Aspergillus section Nigri, Vitis vinifera, Winemaking, WINE GRAPES, FUNGI, RISK