Sensory characterisation of Bordeaux red wines produced without added sulfites

Aim: The evolution of consumer expectations has led to the development of new production methods using low inputs. From an oenological point of view, these methods include the production of wines without any SO2 being added throughout the process. These wines are becoming very popular among consumers, but the absence of SO2 during winemaking increases the risk of stability problems. Such wines have been poorly explored in the literature and there is thus a real need for them to be characterised. This study was developed to evaluate whether Bordeaux quality wines produced without added SO2 have their own typicality, and it provides an insight into current wine production. Methods and results: From a batch of fifty-two commercial Bordeaux red wines produced without adding SO2 and twenty red wines made according to the usual winemaking methods, a selection tasting was performed to eliminate wines with at least one defect further to a sensory space evaluation. In a second phase, the Napping test was applied to defect-free wines to evaluate the sensory specificities of wines produced without SO2 addition. The wines without SO2 addition presented a much higher frequency of defects than those with SO2 (70 % vs 15 % respectively). Defects described in wines without added SO2 were: “Oxidation” (47 %), “Volatile phenols” (31 %), “Mousy off-flavor” (10 %), “Reduction” (8 %) and “Vegetable” (4 %). Since the study focused on quality wines with or without SO2 addition, it was difficult for the tasters to discriminate between them according to their overall technical pathway. Conclusion: This approach has revealed that despite the large number of “non-added SO2” wines with defects, upon blind tasting, expert tasters highlighted some “non-added SO2” wines without defects. Nevertheless, at equivalent quality levels within the same geographic region, and in non-targeted sensory tests, wines with and without SO2 addition were considered to be quite similar. Significance of the study: This study was a first sensory step toward the objective characterisation of “non-added SO2” wines, enabling further work to highlight markers of quality in wines without SO2 addition and to develop the production of “non-added SO2” wines without defects. Nevertheless, at this stage, our results show that the absence of sulfites during the whole winemaking process, including bottling, increases the risk of the development of defects.