New Insights Into The Relationship Of Wine, Oxygen, And Wine Closures - Part 2

Dr Stéphane Vidal - Inter-Rhône

"Controlling bottling or guaranteeing monitoring of wine from the vat to the consumer"

Inter Rhône has set up three lines of work for the study of the corking process:

• Customer accountability by means of upstream quality monitoring
• Analytical approach (direct [O2 dissolved in the head-space] and indirect assaying [SO2, polyphenols, aromas and tasting] + TCA)
• Studies (closure tests, crash test)

Over 7 years of upstream quality monitoring, 30% of the wines deemed non-compliant had taste defects related to cork taint and 30% displayed oxidized characteristics. Inter Rhône therefore set up an independent closure test study. The tests were performed over a 2-year period and involved the closures described in table 1 below. Two storage methods were used: horizontal or vertical, with two Grenache wines from 2002 (Côtes du Rhône and Tavel).

Closure type	Coding	Closures models used	Average dimensions from 20 measurements
Injection molded polymer	P1I	Integra	21.4*38.8
Injection molded polymer	P2T	Tage	22.20*37.8
Injection co-extruded polymer	P3N	Nomacorc	22.02*43.23
Cork-based technical closure	TEC	Omega	22.9*44.0
Double ring composite	1+1	Twin Top	23.7*45.1
Agglomerated cork	AGG	Agglomerated	22.7*38.2
Cork closure	NAT	Cork 3rd Colmated	23.8*44.7
Screw cap	VIS	Stelvin

Table 1: list of closures used in the study.

It should be noted that the closures were selected irrespective of price or suitability of the closure to the type of wine. This study revealed the following main points: Vertical Storage:

• A significant increase of volatile acidity and DO420 nm, oxidation
• A significantly greater loss of free SO2 and CO2, oxidation
• Sealing: analytical degradation of wines tested for all the seals

There is no ideal closure, but some trends are revealed: 1. Agglomerated corks are to be avoided. 2. Technical closures: good closure capacity, but care must be taken with guarantees for batches. 3. Restrict the Tage closure to short-term wine preservation. 4. For the others: 1+1, Nomacorc, Integra, Colmated cork and Screw cap: no significant difference. 5. TCA must be controlled with regard to the bark cork closure. 6. Think in terms of distribution channel and cost analysis in relation to the type of product. Lastly, it is important to consider that whilst the type of closure is a vital element in maintaining wine quality, all work upstream of bottling (pumping, tartaric acid stabilization, filtering, and packaging) as well as bottling are also decisive factors. Pierre Dubrion - Vignobles James Herrick “The practical reasons for choosing co-extruded closures” The Vins de Pays d’Oc produced by Vignobles James Herrick are mainly exported to the English retail chains and cover the premium to super premium segments (£4-6). As such, the wines are fruity and expressive. The whites are distinguished by their crispness and the reds by their supple tannins. Considering the nature of these wines, a closure that preserves the fruit and limits the risk of oxidation is necessary. Following problems encountered with the use of cork closures (faulty taste notes, early oxidation, lack of consistency), it was decided in 2000 to find an alternative to traditional closures. Therein, the company capitalized on the tests carried out since 1990 by its parent company in Australia, Southcorp Wines. Physical-chemical analysis, tasting and ergonomic tests led to the validation of the nomacorc® closure for 90% of bottled volumes. To illustrate, tables 2 and 3 below show the results of comparative testing between bottles closed with a screw cap, reputed to have low permeability to O2, and a nomacorc® closure.

After 12 months’ storage, the bottles closed using nomacorc® displayed levels of free SO2 and residual CO2 that were equal or higher than the values observed for the bottles closed with screw caps. Once the type of closure is defined, special attention must also be given to the bottling conditions, especially with regard to:

• The quality of the corking machine.
• The negative pressure in the corking machine (- 0.5 to – 0.9 bar) and in the head-space (0 to – 0.3 bar). • A sufficient head-space volume (> 12mm).
• The wine’s temperature on filling.
• The inverting of the bottles

On the one hand, the quality of closure must not detract from the necessity to protect the wines before bottling, involving the use of sufficient levels of SO2 and ascorbic acid, or via the transfer and preservation of the wine in inert gas. All these conditions limit the dissolved O2 input on bottling to a value of less than 1 ppm. In conclusion, after 6 vintages closed using nomacorc®, Vignobles James Herrick is happy with their choice, for the following reasons: - The ease of use (no specific bottling equipment required) - The safety offered by the chosen closure system providing seamless protection of the wines - A 100% decrease in customer returns Finally, on the markets concerned, the synthetic closure does not dissuade consumers from making a purchase.

Dr Olav Aagaard – Nomacorc

"Reproducible control of OTR through the closure: Nomacorc’s experience"

During the International Wine Challenge 2006, out of 13,477 wines tested, 7.4% displayed defects. Almost half of these defects were linked to closure problems, broken down into 28% displaying cork taint, 24% oxidation and 30% reduction. So oxidation and reduction of wines is a serious problem which leads to a substantial loss for the industry. The type of problem observed reveals the vital importance of appropriately managing the amount of oxygen in wine. Considering that all wines have different propensities to accept different quantities of oxygen that are beneficial in terms of quality, the real challenge for the industry lies in its ability to implement a reproducible and specific control of oxygen transfer through the closure during storage in bottles.

As illustrated in figure 4 below, certain wines require closures with a high Oxygen Transfer Rate (OTR) to reach optimum quality on consumption. On the contrary, for other wines, it is necessary to promote anaerobic storage conditions and therefore to choose a closure that is less permeable to oxygen (low OTR).

Scientific data currently available in literature reveals compliance with oenological constraints associated with differing wine compositions, requires a range of closures providing different OTRs. Also reproducibility is absolutely essential to ensure consistent wine quality and hence positive consumer response. Figure 5 summarizes the OTRs and the variability of this value observed for different types of corking system. It is the result of compiling the various results extracted from literature (PECK J., 2005; LOPES P. et al., 2006; GODDEN P. et al., 2005, Nomacorc Internal results).

To illustrate, the results presented in figure 6 are related to comparative tests conducted at the Geisenheim Institute in German on Riesling. They clearly demonstrate that: - The closures display different OTRs, with the screw caps and nomacorc® Premium being the least permeable to oxygen. - From one type of corking system to another, the variability in the OTR measurement is different, with nomacorc® closures generating the most reproducible measured values. 708090100110120141618202

In short, the average OTR value of a closure is a practical indicator from which to predict the average conservation period of a wine.

• The propensity of a wine to require a more or less higher OTR for its conservation depends on the grape variety, winemaking processes, management of bottling and marketing positioning. Nomacorc markets a line of closures with different average OTRs (Light, Smart, Classic and, to be launched in 2007, Premium)
• The variability of the OTR is a direct measurement of the reproducibility from one bottle to another. This parameter is essential to ensure consistent consumer satisfaction and hence positive brand recognition. Nomacorc produces closures with a low variability from one closure to another.

Conclusion Consumers are seeking wines that are fruity, faultless and consistent in quality, rejecting oxidized and reduced wines. Controlling the reduction and oxidation (redox) potential has therefore become crucial. Such being the case, this potential is mainly defined by the polyphenol composition of the wine.

This composition varies from one wine to another, leading to variation of the redox potential. The Oxygen Transfer Rate (OTR) through the closure must take into consideration, the redox potential specific to each wine in order to ensure optimal quality and consistent consumer enjoyment.

The challenge for the wine industry and for the closure industry therefore lies in being able to offer a range of closures that display different OTRs that can be reproduced from one bottle to another. Nomacorc, through its current closure range, provides a controlled and reproducible transfer of oxygen. As a result, wine professionals can already adapt their choice of corking system to the characteristics of the wine to undergo closure.

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