Fate of Ochratoxin A during Vinification of Semillon and Shiraz Grapes

Abstract

Semillon and Shiraz grapes containing ochratoxin A (OA) were obtained by inoculation of bunches on the vine with Aspergillus carbonarius. Citric acid content was greater in the inoculated grapes than in healthy grapes. Samples were collected throughout vinification of these grapes and the OA content was quantified using a stable isotope dilution liquid chromatographic-tandem mass spectrometric method. The mass of processed and waste streams during vinification was also noted. Reduction in the amount of OA in juice and wine occurred at every solid-liquid separation stage. The OA concentration (microg/kg) in white and red wine after racking was 4% and 9%, respectively, of that in crushed grapes. This corresponds to 1% and 6% of the total OA content that was initially present in the inoculated grapes. The OA content was divided between solid and liquid phases at each stage of vinification. OA did not appear to be transformed either chemically or biologically by yeast during fermentation, rather was discarded with the marc, juice lees, and gross lees.

Managing ochratoxin A risk in the grape-wine food chain

“…In contrast, Rousseau (2004) reported that OTA content in must increased after grape crushing and reached maximum levels during malo-lactic fermentation. Leong et al (2006b) reported that 24% of OTA originally present in crushed red grape passed into free run wine (must) and a 72% OTA reduction was recorded in wine after the first racking.…”

“…Due to unavailability of naturally contaminated grape some of these studies were performed either by artificially inoculating grape with toxigenic A. carbonarius (Leong et al 2006b) or by spiking uncontaminated grapes with OTA (Fernandes et al 2003). These materials differ from naturally contaminated grapes, which comprise both contaminated and uncontaminated berries.…”

“…The separation or inclusion of the biomass in the sample to be analysed has a significant effect on the measured OTA concentration due to the high amount of OTA reversibly bound to the biomass. Indeed, Leong et al (2006b) included the biomass when unsedimented liquid fractions (must and wines before racking) were analysed for OTA. Consequently, the OTA concentrations found in these fractions were much higher than those found in the same liquid fraction analysed after spontaneous sedimentation of biomass (first racking).…”

“…Results of microvinification experiments showed that only 4% of the OTA present in grapes remains in the wine, whereas 95% of the originally OTA is retained on pressed grape pomaces (98% in the skin and 2% in the seeds) and 1% is retained on the lees. Leong et al (2006b) found that 9% of OTA originally present in grapes passed into wine.…”

Aspectos relacionados à presença de fungos toxigênicos em uvas e ocratoxina A em vinhos

“…A clarificação através do uso de gelatina contribui para a remoção de 58% da OTA presente no vinho . LEONG et al (2006b) relataram que 24% da OTA originalmente presente nas uvas maceradas foi transferida para o mosto e uma redução de 72% nos níveis desta micotoxina foram observados após a primeira trasfega (separação da borra). GRAZIOLI et al (2006) encontraram pouca ou nenhuma redução na concentração de OTA no vinho após a primeira trasfega, enquanto uma redução significativa da OTA foi observada após fermentação maloláctica espontânea, ocorrida entre a primeira e a segunda trasfega.…”