Oxygen management during bottling is critical

Initial results of a German study from the  Geisenheim Research Center clearly demonstrate that oxygen control during bottling has a significant effect on wine development. Researchers found that if bottling processes weren’t managed appropriately, it caused irrevocable damage to the wine and its post-bottling development

Consistent with recent findings from a French study that revealed that oxygen transfer rates (OTRs) through a wine bottle’s closure can be a primary influence of wine development over time, this study shows that the combination of controlled bottling and a closure with the appropriate OTR enables winemakers to effectively manage the wine aging process and minimize the occurrence of fault and inconsistency.

Initiated by Nomacorc, a leading producer of alternative wine closures, and carried out by the Geisenheim Research Center, the study began in July 2008. It explores the influence of different bottling conditions on Riesling grape development, specifically:

• The range of oxygen that a wine can be exposed to during bottling
• The influence of bottling conditions on headspace oxygen content
• The impact of headspace oxygen content on wine development
• How wineries can protect their wines against oxidation

“Ultimately, we found that if bottling conditions are well-managed, then oxygen transfer rates (OTRs) through the closure influences wine evolution in a more pronounced manner,” said Dr. Stéphane Vidal, global director of enology for Nomacorc. “Conversely, before winemakers can shape wine evolution through closure OTR, oxygen ingress at bottling must be under control.”

Research setup and the role of headspace

To accurately monitor oxygen pickup and evolution in this study, Nomacorc and the Geisenheim Research Center used *PreSens Fibox analysers, which allow non-invasive measurement of total package oxygen concentration during the bottling process and other winemaking stages. Total package oxygen is the term used to define the sum of oxygen present in the headspace, dissolved in the wine, and introduced through the closure.

“Our results show that headspace oxygen, which has largely been ignored by the industry, is a very critical factor impacting wine development and more specifically, a wine’s oxidation resistance influencing shelf-life performance,” said Dr. Rainer Jung, scientist and vice chair of the section of enology and wine technology at Geisenheim Research Center. 

Historically, the industry has focused exclusively on monitoring dissolved oxygen levels during bottling due to the inability to measure in tandem the headspace oxygen content. It was believed that because the headspace volume is rather small, its oxygen content would be insignificant compared to the dissolved oxygen. Using the PreSens technique, the Geisenheim research determined that the headspace in fact represents a significant reservoir of oxygen that contributes to wine evolution. As a result, winemakers measuring only dissolved oxygen underestimate the risk of oxidation in their wines.

The research project design evaluated the evolution of a Riesling under different bottling and post-bottling conditions. Bottles were filled using two headspace volumes, each containing three different concentrations of oxygen emulating conditions typically encountered during actual bottling. The wines were then exposed to three closure conditions with varying OTRs. 

Interpretation of Findings

Under multiple conditions, the levels of oxygen measured during bottling ranged from a low of .5 mg oxygen per bottle to a high of 6.0 mg oxygen per bottle – a dramatic variance that can impact a wine’s shelf life by several months.

“By optimising certain processes on the bottling line and diligently monitoring and controlling headspace and dissolved oxygen levels, winemakers and retailers can extend the shelf life of a wine and improve its consistency,” said Vidal. “Once bottling conditions are under control and oxygen ingress is minimized, winemakers can then select a closure with an optimum OTR to drive wine evolution.

“With the new *PreSens tool and our research findings with Geisenheim, Nomacorc hopes to provide recommendations to winemakers that will help them improve the performance of their bottling lines,” added Vidal. “Our intention is to mobilise our team of highly skilled enologists so that they can directly support our customers and assist them in optimising their bottling operations and ensure proper closure selection.” 

Nomacorc’s Oxygen Management Research Program

Related research initiatives at AWRI, Australia; UC Davis, California; Pontificia Universidad Católica, Chile; and Institut National de la Recherche Agronomique at Montpellier (INRA) involving Chardonnay, Cabernet Sauvignon, Sauvignon Blanc, Shiraz, Carmenère, and Grenache varietals are being conducted concurrently, with additional initial results expected this year. The combination of results from all these projects is expected to provide a substantial body of scientific data confirming that OTR is a critical factor in wine development and that appropriate closure selection can improve wine quality consistent with the winemaker’s intention and ensure optimum consumer enjoyment.

*In january 2009, Nomacorc formed an alliance with PreSens Precision Sensing, a manufacturer of optical chemical sensors whereby Nomacorc markets the oxygen measurement equipment developed by PreSens for use in the wine industry.

The first equipment Nomacorc will offer to wineries, bottlers and research facilities is the PreSens Fibox series of analyzers, which allow for non-invasive measurement of total package oxygen concentration during the bottling process and other winemaking stages. The equipment uses proprietary photo-luminescent technology with small sensors that can be easily used in most any bottling condition. These sensors respond very accurately to differing levels of oxygen concentrations and can be used to measure both dissolved oxygen and headspace oxygen in the bottle.

May 09

1 May 2009 - Felicity Murray