Impact of eight closures in controlled industrial conditions on the shelf life of two (red and rosé) wines

摘要

Aims: The management of O2, CO2 and SO2 at bottling and the choice of closure are two key factors of the shelf life of bottled wines before bringing them to market. The impact of eight closures (four screw caps, two synthetic stoppers and two technical stoppers) was evaluated on a red Merlot/Tannat wine. The results of a rosé wine are also discussed.Methods and results: Analytical monitoring (O2, CO2, SO2, aphrometric pressure, L*, a*, b*) was carried out over 538 days of storage at 20°C, along with two sensory analyses at 10 and 17 months. The average wine total O2 content at the time of bottling was 2 mg/L. Intra- and inter-procedure variability was controlled, including for dissolved CO2 content.Conclusion: Unlike closures with the highest Oxygen Transmission Rate (OTR), the two technical stoppers and the two screw caps with Saranex seal, harboring the lowest OTR, matched with the wines exhibiting a low total O2 content at equilibrium (from 4 to 18 months after bottling), with more free SO2 and less color change. However, the OTR gradient (5 to 67 μg/d) observed through the physicochemical analyses was not necessarily confirmed by the two sensory analyses.Significance and impact of the study: This study puts into perspective the impact of closure OTR on the sensory characteristics evolution of wine consumed within the first two years, especially when total O2 at bottling exceeds 1.5 mg/L. Introduction Oxygen is one of the main factors for wine’s evolution. At bottling, the level of oxygen captured in the headspace (HSO) and dissolved in the wine (DO) must be reduced as much as possible. The Oxygen Transmission Rate (OTR) of closures then regulates the transfer of oxygen inside the bottle after bottling. Thus, the management of O2, CO2 and SO2 at filling and the choice of closure act as key factors of the shelf life of bottled wines.Oxygen ingress during and post bottling leads to a loss of sulfites. In wine, the reaction between O2 and SO2 is extremely slow (Waterhouse and Laurie, 2006). Sulfites react with the products of wine oxidation and in particular with hydrogen peroxide, produced from the oxidation of phenolic compounds (Danilewicz et al., 2008; Danilewicz and Wallbridge, 2010). The wine becomes more sensitive to oxidation and ages faster. Godden et al. (2001) highlighted a critical concentration of free SO2 of 10 mg/L below which a Semillon wine is perceived as substantially affected by oxidized aromas. For red wines, controlled oxygen ingress is necessary and variable according to the expected quality before and after bottling, especially to avoid reduction (Caillé et al., 2010; Ugliano et al., 2012).The commercial choice between stopper (natural, technical or synthetic) and screw cap has a direct impact on the volume and inerting process of the headspace as well as the OTR of closure. The volume and technical management of the headspace (vacuum, gas sparging, snowdrop) explain that the quantity of oxygen trapped in the headspace can vary from 0.4 to 3.6 mg/bottle (bt) (Vidal and Moutounet, 2006). The bottling line audits outlined by O’Brien et al. (2009) confirm this broad range of oxygen amount. Kontoudakis et al. (2008) showed that stopper type significantly affected the HSO content. The headspace volume of a corked bottle is significantly lower than that of a capped bottle, but on the other hand the cork releases part of the oxygen trapped in its own structure due to the compression of the stopper in the bottleneck (Squarzoni et al., 2004).Regarding bottle storage position, there is no consensus to date on an effect on oxygen mass transfer through the closure and wine aging over time, even if, in theory, the oxygen diffusion coefficient through the closure into the wine is smaller than into the headspace. Mas et al. (2002) concluded that white and red wines were best preserved when bottles were stored horizontally rather than vertically. Puech et al. (2006) on rosé and red wines and Skouroumounis et al. (2005) on white wines found no significant difference. Godden et al. (2001) concluded that upright storage tended to accelerate SO2 loss from a Semillon wine, but in many cases this effect was marginal.The principal methods for determination of wine closure OTR are the coulometric method by Mocon Oxtran with nitrogen flushing of the inner face of the cell (ASTM International, 2014), the differential permeability method with pressure difference between both ends of the stopper (Sanchez and Aracil, 1998), the luminescence method on corked or capped bottles filled with nitrogen or deoxygenated acid water (Diéval et al., 2011; Vidal et al., 2011), and the colorimetric method with indigo carmine (Lopés et al., 2005). The Mocon Oxtran technology is by far the most commonly used in the packaging industry. But when applied to the bottle/closure system, it cannot exactly mimic the storage conditions where the closure is in contact with the wine (horizontal storage) or in contact with the water vapor