Incidência de ocratoxina A em vinhos e a correlação de fungos do gênero Aspergillus e Penicillium com as características físicoquímicas de uvas viníferas da região tropical semiárida do Brasil

Abstract

Grapes (Vitis vinifera L.) are subject to contamination by filamentous fungi present in crops, during harvest and winemaking, Aspergillus being the main producing genus of ochratoxin A (OTA) in grapes. The incidence of fungi and toxin levels vary depending on the variety of grapes, the winemaking region, agricultural practices, weather conditions, harvest and the winemaking process. Thus, this study aimed to evaluate the diversity of Aspergillus and Penicillium fungi isolated from the grapes and the cultivation soil in the São Francisco Submidle Valley winegrowing region, the presence of OTA in experimental wines, as well as if there is a correlation between the occurrence of Aspergillus and Penicillium fungi and the physicochemical characteristics of the wine grapes grown in the region. Samples of grapes and soil from the vineyards were collected from the 2/2014 and 1/2015 crops. For the isolation of filamentous fungi from the grape berries, the direct plating technique in DRBC culture medium was used. For soil samples the surface-spreading technique in DG-18 medium was used. The Aspergillus and Penicillium species were identified by morphological characteristics and the presence of OTA in experimental wines was detected by HPLC. The physicochemical characterization of the grapes was also performed. Contamination of vineyard soil ranged from 2.34 x 10³CFU/g to 4.35 x 104CFU /g. The species found in the wine grapes were Aspergillus niger, A. carbonarius, A. aculeatus, A. niger Aggregate, A. flavus, A. sojae, Penicillium sclerotiorum, P. citrinum, P. glabrum, P. decumbens, P. implicatum and P. solitum. All of A. carbonarius isolates, 18.18% of A. niger, 14.29% of A. niger Aggregate and 60% of A. ochraceus were OTA-producing fungi. All A. parasiticus were producers of B1, B2, G1 and G2 aflatoxins, whereas only 14% of A. flavus were producers of B1, B2 aflatoxin. All P. citrinum were citrinin producers. The highest OTA concentration was found in red wine (0.29μg / L) and in white wines it ranged from 0.02 to 0.04μg / L. All identified species in this study showed a positive correlation with at least one evaluated physicochemical parameter, highlighting the pectin content, total sugar, total acidity and phenolic compounds. It was observed that the fungi incidence and OTA levels vary according to the variety of grapes, cultivation methods, weather conditions and crop.