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75 per cent of red wines from Bordeaux that have been vinified without sulphur have sensory defects. This is the result of a French study presented by post-doctoral researcher Edouard Pelonnier-Magimel from the University of Bordeaux at the Oenofutur conference in Montpellier.
"We bought 52 wines from the 2015 and 2016 vintages labelled without added sulphur from supermarkets, wine merchants or directly from the winery," he explained. In parallel, he and his team recorded wines that were equivalent in terms of price, geographical region and wood influence, but contained sulphur.
The researchers first analysed the total SO2 in all the wines. They found that "only 43 of 52 wines that were free of added sulphites according to the label complied with the limit of 10 mg/l. Four even contained more than 30 mg/L and were excluded from the study", Pelonnier-Magimel explained. The remaining wines were tasted blind by eight oenology students with very good Bordeaux knowledge. Thereby, 75 percent of the wines without SO2 addition were classified as faulty by at least three tasters. According to the study, most of the wines were oxidised, 25 per cent had Brettanomyces notes and 14 per cent had mousse aromas. In contrast, only 25 per cent of the sulphured 2015 wines had faults, and for the 2016 vintage, all were aromatically flawless.
23 tasters then blindly sorted out the flawless wines. They were able to distinguish between the sulphured and sulphur-free wines in terms of smell and taste without any problems. In the triangle tests that followed, they described the sulphite-free wines, regardless of the vintage, "as fresher, with more intense aromas of mint, blackcurrant and cooked cherry. Conversely, the sulphited wines were perceived as smokier," Pelonnier-Magimel explained.
In the following chemical analyses, the researchers found more of the aroma-intensive methyl salicylate in wines that were vinified without sulphites. It produces a pungent camphor aroma in the wine that is otherwise only found in wine from grapes in poor health. Further research should clarify why these notes develop.
(uka / Source: Vitisphere - Photo: 123rf)