|
A Technical Guide for Wine Producers
|
|
RECENT ARTICLES | WYNBOER HOME
WHAT'S UP IN THE VINEYARD AND CELLAR
Oxygen ingress during bottling and storage
Wine chain logistics extend from the vineyard to the bottle of wine that is purchased by the consumer. Viticulturists and winemakers go to great lengths to ensure that the grapes are received at the cellar at optimal ripeness; moreover, vinification processes are applied and managed in such a way that the quality of the final product is above suspicion. It often happens, however, that the bottling and packaging processes of the wine are handled by another party such as a mobile bottler or another division at large companies. It is extremely important for activities such as these to be executed with the greatest possible care to maintain the level of dedication that formed an initial part of the logistics chain. The possibility of oxygen ingress during bottling is one of the greatest sources of quality problems.
Oxygen ingress exerts considerable influence on the sensorial qualities of wine. The so-called fruit-driven wines that have become so popular in certain markets in recent years are particularly exposed to the negative effect of unnecessary oxygen ingress.
In wines that are stored in an upright position, the ingress and impact of oxygen may be summarised as follows:
Various factors influence the above-mentioned movements. The movement through or around the bottle closure may be the result of a closure per se that is not tight, or contact surface with the bottle that is not tight. Both problems are exacerbated by vacuum bottling where the pressure outside the closure is higher than the pressure inside the bottle. Increased temperature also promotes the mobility of the oxygen molecules. In order to prevent potential problems, the suppliers of bottle closures and winemakers should have the necessary equipment to evaluate the oxygen permeability of bottle closures on the one hand, while on the other hand winemakers should monitor the oxygen status of wines throughout the production chain (O’Brien, 2007).
The amount of oxygen and the tempo of ingress determine the extent to which the wine component that reacts to it, will change and therefore influence the sensorial qualities of the wine. Oxygen in the wine may increase during or after bottling by means of oxygen that is present in the filling cavity, oxygen ingress during the filling process and oxygen entering the wine through the bottle closure during storage. All bottle closures in a particular closure group such as corks, screw caps, plastic closures, metal closures and closure linings do not necessarily react the same. For example, the characteristics of screw cap linings such as Saranex and tin vary considerably and the elasticity of many natural and synthetic corks after closure of the bottle is unpredictable. It is also interesting that the most common bottle closure problems in the wine industry will never be acceptable in any other liquor industry.
The term Total Oxygen Pickup (TOP) is commonly used in the food and liquor industries to monitor the oxygen ingress during the filling process and subsequent storage. In the case of bottling this includes oxygen ingress in the bottling tank, wine hoses, turbulence in the filling reservoir, the exposure of wine to air during the filling process, air in the bottle filling cavity and migration through the packaging. It is usually measured in parts per million (ppm) or parts per billion (ppb). It may be monitored by measuring the dissolved oxygen quality at different stages in the course of the filling process. The basic stages that should be measured, are the bottling tank outlet, bottles that have just been filled and those that have just been sealed. The sampling may be extended to the top of the bottling tank, filter and filling machine to ensure more comprehensive monitoring.
As may be expected, oxygen ingress in wines that have been bottled with screw caps is considerably less than in those with natural or synthetic cork closures. There is not a marked difference, however, in the oxygen ingress in wines that have been bottled with natural or synthetic corks.
Ways of limiting oxygen ingress in wine during bottling will be discussed in a subsequent article.
References:
Crochiere, G.K. 2007. Measuring oxygen ingress during bottling/storage. Practical Winemaking, January/February 2007: 74 - 84.
|
|
Wynboer is incorporated in WineLand, magazine of the SA wine producers.
Visit our sister sites:
|
| UP |
COPYRIGHT (C) 2000 WineLand |