Effects of bottle closure type on sensory characteristics of Chasselas wines

Abstract

Several winemaking operations, such as filtration, pumping, and racking, are known to potentially facilitate the incorporation of atmospheric O2 into the wine. Control of grape must oxidation is one key aspect in the management of white wine aroma expression, color stability and shelf-life extension. On the one hand, controlled must oxidation may help to remove highly reactive phenolic compounds, which otherwise could contribute to premature oxidation. And on the other hand, in certain cases of extreme protection of the must from O2 (e.g. pressing under inert atmosphere), it can help to preserve varietal aromas and natural must antioxidants. Although must handling is done at the very beginning of the winemaking process, exposure of the must to O2 at this early stage is profoundly connected with other steps at a much later stage of the winemaking process, this is particularly true for post-bottling O2 exposure and therefore bottle closure selection. Post-bottling wine ageing is a slow and complex process, in which the bottle closures play a fundamental role, due to their O2 permeability. During this period, sensory characteristics of the wine are likely to change as a result of the exposure to O2. For these reasons, increasing numbers of industry professionals agreed that consistent O2 transmission is important and that chosen bottle closures should be matched with the wine type. The aim of this work was to determine the impact of dissolved oxygen and bottle closure oxygen transfer rates on the evolution of wines made from Chasselas grapes with different levels of O2 protection (protected and surexposed). The resulting wines were bottled with different amounts of dissolved O2 (DO) and sealed with three different corks (two co-extruded and one agglomerated type) and one screwcap. O2 measurements were taken after bottling on a weekly bases during the first month of storage, and after 1, 3, 6, 12, 18 and 22 months after bottling. The evolution of total O2 transfer through identical closures into empty bottles, previously purged with nitrogen was also investigated. As already described, FSO2 decreased during bottle storage, with a rapid decline in the first 3 months followed by a slower decline after 6 months of storage. The extent of FSO2 decline was essentially affected by DO at bottling and by must management. A panel of 20 judges was trained to carry out a sensory evaluation of the wines, by Flash Profile and Napping, 6, 12, 18 and 22 months after bottling. Beyond the period of 12 months, oxidative and reductive profiles could be observed mainly related to the type of closure and to must management. At 22 months, discriminatory tests allowed us to distinguish the impact of each closures. These preliminary results are expected to increase our understanding for the optimum balance of pre-fermentative/post-bottling O2 exposure of Chasselas wines, and help guide winemakers in their choice for the perfectly adapted bottle closures.