Technical Letter | 05

Optimize wine post-bottling development: Total Package Oxygen (TPO) and the importance of headspace oxygen Enology team

In today’s rapid turnaround market, there is a growing using different bottling equipment and closure types. As interest towards winemaking practices that are able to it can be seen, the amount of oxygen present at bottling, give wines that are ready for drinking when they leave typically referred to as TPO (total package oxygen), can the production facility. However, even with these fast consist of several mg/L, in some cases reaching values turnaround times, a period of several weeks or even close to 10 mg/L. Considering that closures currently months intervene typically between bottling and existing on the market cover a rage of approximately 0.5- consumption of wine, during which wine sensory 5 mg O2/bottle/year, these values are equivalent to the characteristics can change as a result of the different amount of oxygen that will permeate through a closure chemical reactions taking place. Overall, it is often said over several years. It can be therefore deduced that TPO that wines reaches a balance after some time in the bottle, represents a highly significant component of the oxygen provided that adequate conditions exist, including having seen by a finished wine in its entire life. The following appropriate levels of oxygen. discussion is aimed at showing the influence of TPO on wine evolution, illustrating how correct management of The type of closure, and specifically its OTR (oxygen TPO is a key ingredient to achieve consistent post-bottling transmission rate) value is certainly a major factor evolution. contributing to oxygen exposure in the bottle (see Nomacorc Technical Newsletter #1-#4). However, although Dissolved and headspace: the components of TPO very important, closure OTR is not the only factor influencing wine exposure to oxygen inside a sealed Figure 1 also shows, for each of the TPO measures taken, bottle. Figure 1 shows a set of data collected at different the split between dissolved oxygen (DO) and headspace wineries by means of the oxo-luminescence-based oxygen (HSO). While DO is often higher than HSO, this Nomasense® oxygen analyzer, during bottling sessions cannot be generalized, as several instances were found

www.nomacorc.com NomaSense - Technical Letter | p.1 where, in spite of a low DO, TPO was still high due to high From a practical point of view, excessive DO or HSO levels, HSO. This is of great interest, given that most wineries although part of the same problem, have very different tend to rely on DO measures to assess their overall ability origins and require very different cures. Leaving aside to keep oxygen under control. While this is correct for issues of high DO related to inadequate storage and monitoring of oxygen exposure throughout the transfer conditions, DO levels in the bottle can often winemaking process, when it comes to bottling reflect oxygen pickup during bottling operation, for performances the measurement of DO alone is obviously example at the level of individual filler heads. This can be not sufficient anymore, and HSO should be taken into the source of a relatively high variation in TPO at bottling, account. as it can be observed in Figure 2.

From the data in Figure 1 it can be observed that too high Conversely, HSO values are linked to the performance of TPO values can be common to all closure types, regardless the inerting devices that are active on a bottling line (e.g. of whether they are cylindrical (e.g. natural cork, nitrogen sparging, vacuum, etc). Malfunctioning of these agglomerated cork, synthetic co-extruded, injected devices can be rather common, but it is difficult to assess molded) or screw cap. TPO values are linked to good as it requires measuring the oxygen concentration in the conditions of storage and handling of the wine to headspace of a sealed bottle. minimize DO pickup prior to bottling, as well as to optimal functioning of inerting equipment at bottling. It Implications of TPO for wine post-bottling seems therefore logical that the type of closure has a development secondary influence on TPO. However, a trend seems to exist in this dataset, with screw caps always being affected From the previous discussion, it appears clear that, from a by relatively higher HSO (average HSO for screw cap 3.66 quantitative point of view, TPO is a major component of the mg/L, compared to 1.54 mg/L for other cylindrical and pool .The question arises therefore as to whether above- 1.27 mg/L for Nomacorc). This reflects probably the fact average TPO levels can significantly affect wine shelf-life. that, in screw capped bottles, headspace volume is much larger, and oxygen is more difficult to remove. Additionally, The influence of HSO management was investigated in a the air trapped under the screw cap can be conveyed back series of studies carried out by the Geisenheim Research into the bottleneck upon application of the cap, further Institute in partnership with Nomacorc. The experimental contributing to higher HSO. design adopted is shown in Figure 3. Wines were bottled

with different HSO values by different degree of CO2 flushing of the headspace

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HSO=0.4 mg/L; TPO=1.5 mg/L

Bottle filling Riesling DO 1.1 mg/L HSO=2.9 mg/L; TPO=4 mg/L wine Headspace volume 6 mL

HSO=5.7 mg/L; TPO=6.8mg/L Figure 3. Experimental design used for the study of the influence HSO on bottle aging of Riesling wine. 375 mL bottles were used

The HS volume of 6 mL represents typical industry case, in wines for rapid consumption. The direct settings for cylindrical closures. However, as 375 mL connection between initial HSO and loss of SO2 suggest bottles were used in this study, the levels of oxygen that TPO management could be of primary importance to contained in these headspaces (expressed in mg/L wine) increase the shelf-life of low-SO2 wines which are highly would be 50% lower if 750 mL bottles were used. When sought by today’s consumers, including organic and HSO values are calculated for 750 mL bottles, final values biodynamic wines. of 0.2, 1.45, and 2.9 mg/L wine are obtained for the three inerting levels. It can be concluded that the range of HS However, the importance of TPO is not restricted to short oxygen concentrations in this study is similar to that term scenarios, as variations in TPO can result in changes found in other studies. Therefore, although obtained in in wine aroma profiles that will manifest after longer an experimental setup, the observations of this study bottling periods. Sensory analysis carried out on the provide meaningful indications regarding bot¬tling wines after 24 months of bottle storage at 14°C is shown management in large-scale winemaking. in Figure 6. Wines with the lowest and highest HSO levels were found to be different in the intensity of the

Free SO2 evolution was followed over time during bottle ‘developed’ character, with wines bottled with lower HSO aging (375 mL bottles were used for this study). Results having lower developed notes and higher overall for the three HSO levels studied are shown in Figure 4. impression. Differences in the ‘reduction’ attribute were negligible.

When it comes to wine post-bottling development, closure

oxygen permeability (OTR) is not the only factor affecting

the evolution of wine in the bottle. TPO (total package

oxygen), namely the sum of dissolved (DO) and headspace (HSO) oxygen present at bottling can play a major role.

Too high TPO, often resulting from excessive oxygen

pickup during bottling operations, is associated with

premature loss of SO2, and uncontrolled TPO variations can determine significant bottle to bottle variation. Monitoring of TPO is crucial to reduce unpredictable variations during bottle storage, and could provide a

powerful mean to ultimately reduce SO2 doses at bottling. Initial HSO (and therefore TPO) had a great influence on the decline of SO2 in the first 4 months. HSO values of 5.7 mg/L resulted in a loss of free SO2 of 32 mg/L (> 50% of 5 the initial value) in this timeframe, while in the case 0.4 0,5 mg/L HSO 4 5,7 mg/L HSO mg/L HSO only 15 mg/L were lost. Interestingly, free SO2 loss between four and fourteen months of bottle storage 3 Intesnity was comprised between 6mg/L and 8 mg/L, corresponding 2 to about ¼ of the free SO lost in the first four months 2 1 under conditions of high HSO at bottling. This indicates 0 that TPO at bottling plays a primary role in the evolution Developed Reduction Overall impression of free SO2 in the first months after bottling, highlighting Figure 5. Sensory attributes of Riesling wines after 24 months of bottle storage (375 mL bottles) the importance of TPO components, such as HSO in this

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