By Enology Team, Vinventions, France

To be adapted to the corking of wines and to optimally conserve them, a stopper must possess a certain number of properties such as:

• Mechanical properties adapted to allow bottling, and then opening of the bottles by consumers.
• Compliance with regulations governing materials in contact with foodstuffs.
• The absence of contamination by defect molecules, such as TCA.
• Defined and uniform permeability to gas, particularly oxygen, within a batch of closures and between batches, which underpins the performance of wine preservation.
• Finally, aesthetical qualities and sustainable development, to meet image and corporate policy requirements.

SÜBR closures are micro-natural stoppers, which is a new category of closures, made up of granules of cork and other plant-based materials that are biodegradable, with a traditional quality visual. They are designed to be recyclable (polyurethane free) and are also without defects / cork tainting.

This document reports on the results obtained during wine conservation trials using SÜBR in comparison with other stoppers. It provides proof of the low permeability of SÜBR closures, their excellent uniformity and their ability to preserve wines over time.

Method

Permeability measurements on closures

The permeability was laboratory measured according to the method described by Diéval et al (2011). Called “Oxygen Ingress” (OI), it allows determination of the desorption of O₂ for closures when they are inserted in the bottle as well as the ingress of O₂ through the closure.

Monitoring of wines stoppered with Sübr and other closure solutions

Bottling

Each time the wine was bottled, the total package oxygen was measured using the Nomasense O₂ P300 (Wine Quality Solutions). The total package oxygen is the sum of dissolved oxygen and head space oxygen.

Analytical monitoring of wines

The bottles were kept at 14°C, some for up to 55 months. The concentration of free and total SO2 (Methrom), colour (NomaSense Color P100, Wine Quality Solutions) and concentration of dissolved CO₂ (NomaSense CO₂ P2000, Wine Quality Solutions) were analysed periodically. At the same frequency, the bottles were tasted by a jury of experienced experts.

31 trials on red and white wines from various appellations were considered in this study (Chianti, Margaux, Pessac, Médoc, Pic Saint Loup, Jurançon, Pecorino, Sancerre, etc). In addition to the SÜBR closure, each wine was bottled in parallel with other stopers for comparison: Nomacorc Reserva, natural cork or micro-agglomerated closures from different suppliers.

Results

Permeability of SÜBR closures

SÜBR closures display very low and uniform permeability (Table 1), which is perfect for conserving wines capable of long ageing and for guaranteeing better aromatic freshness of more delicate wines to be enjoyed in their youth. Furthermore, the closures’ continuous manufacturing process gives them excellent uniformity within and between batches.

Preservation of SO2 by SÜBR micro-natural closures

The low OI of SÜBR closures makes it possible to limit entry of oxygen into the bottle, which directly results in greater conservation of sulphite concentrations than the majority of other stoppers. Below, Figure 1 displays the average difference measured between the concentrations of free SO₂ in wines conserved with SÜBR closures (used as a reference) in relation to the same wines conserved with the other stoppers featured in the study. For a given value of free SO₂ for a wine conserved using a SÜBR closure at a given moment, the other stoppers in the study displayed on average either an equivalent concentration with Reserva, or a lower concentration with a micro-agglomerated or natural closure. The differences observed are directly related to the level of OI for each of the stoppers, because less O₂ intake into the bottle means there is less oxidation and therefore a lower drop in concentration of SO₂. The OI for the SÜBR closure was in the low range of OI for micro-agglomerated closures and very low for natural closures (Figure 2), which explains the average conservation of SO₂ by the SÜBR closure that was slightly higher than micro-agglomerated closures and much higher than the natural closures used in the study.

These differences appear significant according to the critical probabilities calculated by Wilcoxon test (samples matched per wine). Although the magnitude was smaller for micro-agglomerated closures than for natural ones, it was more significant due to the larger number of individual pieces tested. A similar result was obtained for the concentrations of total SO₂ (not shown here).

Uniformity of SÜBR closures compared to natural closures

Natural closures are inherently not very uniform within and between batches due to the intrinsic variability of cork. This observation was made systematically when comparing the level of free SO₂ for a same wine conserved with a natural closure or a SÜBR closure. Figure 3 illustrates this: after 1 year of conservation, the variability of free SO₂ levels in a wine stoppered with a natural closure was much higher than that observed for the same wine stoppered with a SÜBR closure (measured on 5 bottles).

Organoleptic profile

The organoleptic evolution of wines is related to the permeability of closures. Not surprisingly, given the similarity in permeability of the SÜBR and micro-agglomerated closures, the profiles of wines conserved with these two types of closures were often very similar. Figure 4 shows the organoleptic profiles of a Pessac Léognan red wine conserved for 30 months with SÜBR and micro-agglomerated closures.

In addition, in comparison to natural closures, the use of SÜBR closures, with which the concentration of TCA is guaranteed to be lower than 0.5 ng/L, makes it possible to avoid cork taint or masking of the fruit by TCA present at a level of concentration below its olfactory recognition threshold (Figure 5, left). It also limits the increase in astringency sometimes observed with natural corks (Figure 5, right).

Conclusion

This validation study for SÜBR closures has made it possible to quantify their low permeability to oxygen (called oxygen ingress), making them ideal closures for wines suited to long ageing. Similarly, they enable better conservation of aromatic freshness in wines that are delicate or to be enjoyed in their youth.

SÜBR closures are the only cork-based closures that are extruded to ensure perfect closure-to-closure uniformity and the impact of these qualities on the preservation of SO₂ was verified on the 31 conservation trials carried out as part of this study. The levels of free SO₂ were on average higher for wines conserved with SÜBR closures than with other stoppers, some of which display a higher level of permeability (micro-agglomerated and natural closures). The variability of SO₂ levels from bottle to bottle were also less high than with stoppers that are known to display less uniformity from one closure to another (natural closures).

The organoleptic profiles of the wines conserved with SÜBR closures have validated the excellent capacity of this closure in preserving the profiles of the wines. In general, the profiles obtained with SÜBR closures are close to those obtained with micro-agglomerated closures (in the case where the latter do not display defects). Furthermore, the very low level of TCA in SÜBR closures makes it possible to avoid cork taint that is sometimes observed with natural closures or certain micro-agglomerated closures, as well as the masking linked to this molecule or the appearance of astringent finishes.

Finally, because sustainable development is at the heart of Vinventions’ concerns, SÜBR closures are made from renewable, plant-based and biodegradable raw materials. They are completely polyurethane free and are designed to be recycled.