34 www.winebiz.com.au WINE & VITICULTURE JOURNAL MARCH/APRIL 2012 V27N2 WINEMAKING CLOSURES INTRODUCTION F or nearly 400 years, natural cork stoppers were the standard by which wine was packaged, shipped, and presented to consumers. However, in the 1990s, the increasing awareness among consumers of problems associated with natural cork, such as ‘cork taint’, has encouraged wine producers to seek alternative closures, such as synthetic closures and screwcaps. Although the market share has been eroded since the mid-1990s, cork stoppers still seal around 70% of the 18 billion wine bottles produced per year, while 15% and 20% of bottled wines are sealed with synthetic closures and screwcaps, respectively (Bates 2010). The wine industry still expresses some hesitation with alternative closures, due to the evidence that cork stoppers have the most appropriate properties to seal wine bottles, which contrasts with the less-than-ideal barrier properties of synthetic closures and screwcaps (Godden et al. 2005). Since the cork industry has enhanced its reliability in delivering untainted corks in recent years, the perception and status of cork stoppers has improved, which contributed to slowing the movement towards screwcaps and synthetic closures. Aesthetic considerations and brand image are often among the major selling points for wines, which must be taken into account to ensure consumer acceptance (Mueller and Lockshin 2008). Although closure choice is, theoretically, a technical decision based on its sealing properties, wine producers are also infuenced by the players in the marketplace and consumers preferences. In addition, sustainability and environmental credentials associated with each closure seem, nowadays, to also infuence wine producers’ closure choice, although it is not clear how wine consumers perceive and value the environmental friendliness of each closure. This article aims, primarily, to resume the extensive work carried out by the Faculty of Enology of Bordeaux and also by the Amorim R&D department on the barrier properties of different wine closures, especially in the determination of their oxygen transmission rates and evaluating its impact on the favour, colour and sensory properties of wines post-bottling. The results contributed to elucidating the role of oxygen on wine development during the post-bottling period, and determining the importance of bottling and closure technologies for this phenomenon. Secondly, a brief summary is presented of recent studies about the importance of closures on wine extrinsic attributes, which highlights both the trade’s and consumers’ opinions, and attitudes toward closures and how this can affect their wine purchase decision. BARRIER PROPERTIES OF WINE CLOSURES The primary function of a closure as a part of wine packaging is to ensure a good seal, preventing sensory deterioration of the wine, providing barriers to moisture, oxygen, carbon dioxide and other gases, as well as favours and aromas (Risch 2009). Unlike the glass bottle, not all closures are impermeable materials, and their sealing properties can lead to mass transfer of various small molecules, such as oxygen (Lopes et al. 2007, Lopes et al. 2011). Oxygen transmission rates of closures Lopes et al. (2005) optimised a non- destructive (i.e., a single bottle can be analysed without compromising the closure seal) colourimetric method to measure oxygen ingress into wine bottles. This method infers oxygen ingress through closures by direct colourimetric scan of colourless wine bottles (375mL) containing indigo carmine solutions. The solutions gradually change colour from yellow to indigo as oxygen reacts with the reduced indigo carmine. The method was developed to allow the calculation of the oxygen ingress rate through closures, and the amount of oxygen contained in the closure; the effect of oxygen inserted at bottling was not, initially, taken into account. Figure 1 shows the kinetics of oxygen ingress through different closures into wine bottles stored horizontally over 36 months. It can be observed that only the control (bottle sealed by fame) was completely airtight, while other closures allowed Impact of different closures on intrinsic sensory wine quality and consumer preferences By Paulo Lopes 1 *, Isabel Roseira 1 , Miguel Cabral 1 , Cédric Saucier 2 , Philippe Darriet 2 , Pierre-Louis Teissedre 2 and Denis Dubourdieu 2 1 Amorim & Irmãos, S.A., Research & Development, Rua de Meladas 380, 4536-902 Mozelos VFR, Portugal 2 UMR1219 Oenologie, Faculté d'Oenologie - ISVV, 210 Chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon France. *Corresponding author. Email: pdl@net.sapo.pt Figure 1. Kinetics of oxygen ingress through different closures into commercial bottles stored horizontally over 36 months. Error bars represent the standard deviation of four replicates.