Impact of agronomical and technological factors on the occurrence of atypical ageing (ATA) in sparkling wine production

Traditional sparkling wine (SW) production is a flourishing market that has experienced significant growth over the last few decades. SWs are regarded as premium products characterised by their high economic value. This prestige is attributed to the lengthy and costly manufacturing process involving a double fermentation step and a period of aging sur lie. In this regard, maintaining a consistently high-quality profile is crucial for consumer satisfaction and brand reputation. Any compromise in quality due to sensory faults can jeopardise the marketability of these products and erode their premium image. The appearance of sensorial faults is one of the main threats undermining the quality of SWs. Indeed, once the tirage has been done, the operational capacity of the winemaker to adjust the final result is very limited. Atypical ageing (ATA) is a wine aroma fault characterised by the vanishing of varietal aromas and the advent of unpleasant notes reminiscent of wet mop, dirty rag and naphthalene. These sensory faults can significantly impact the aromatic profile of SWs, diminishing their appeal to customers. Addressing ATA adds complexity to the production process. Winemakers must navigate potential issues during the second fermentation and ageing stages, making it essential to understand the factors contributing to the onset of this defect. Research has revealed that stress reactions in the vineyard, inadequate grape handling and unfavourable fermentation conditions are among the causes that lead to the appearance of this taint. Understanding these factors is crucial, especially considering the competitive nature of the sparkling wine market, where maintaining consistent quality is paramount. This doctoral research aimed to expand the knowledge of the root causes and potential remedies associated with ATA and SW production. The approach involved evaluating the agronomic and technological factors contributing to this defect. This encompassed field experiments, fermentation trials, and chemical analyses utilising an ultra-high-pressure liquid chromatographer coupled to a high-resolution mass spectrometer (UHPLC-HRMS). In addition to investigating the genesis of ATA, a crucial aspect of this research involved the development and validation of an analytical method to quickly and effectively quantify the amino acid (AA) content of oenological products. Since yeast biochemistry is involved in ATA formation, measuring the AA taking part in its formation is crucial. In this regard, specific attention was paid to tryptophan, a known ATA precursor. The method, employing a UHPLC-HRMS, was successfully applied to the compositional studies conducted during the experiments. The first field trial demonstrated that different production management systems (organic versus conventional) did not affect the development of ATA in wine. Conversely, the vintage year emerged as a more influential factor in the onset of this defect. Based on this finding, the second field trial aimed to evaluate the impact of soil water holding capacity (AWC) on ATA development. Interestingly, in a vintage characterised by reduced summer rainfall, grapevines planted on shallow soils (AWC < 70 mm) generated wines more prone to be ATA-tainted. With regard to technological factors, the influence of second fermentation and bottle ageing was investigated and found to increase the likelihood of developing the sensorial fault. The research demonstrated that a simple accelerated ageing test carried out on the base wine is an adequate predictive tool to aid in forecasting the fate of the finished SWs. Furthermore, it was demonstrated how the oxygen radical absorbance capacity (ORAC) assay might help foresee the ATA taint during the commercialisation phase. Finally, considering that yeast derivatives (YDs) are often used during vinification to improve fermentation performance, their involvement in the occurrence of ATA was explored. It was discovered that these commercial formulations contain ATA-related compounds in variable amounts. Depending on their physicochemical composition resulting from the manufacturing process, their addition to grape must before fermentation might enhance or reduce the tendency of ATA appearance. In essence, this research contributes to the understanding of the intricacies of ATA and SW production AND provides valuable insights for winemakers to make informed decisions, ensuring the continued excellence of SWs in a competitive market.