The management of barrel storage rooms is intended to create a stable and controlled environment for wine to age. This article provides a few of the most important guidelines to be followed.
The stacking of barrels
The stacking of barrels can influence the quality of the wine, as well as the effectiveness of space utilisation in the storage room. The following aspects are fundamental:
- Barrels sharing a cradle must have the same form and size. If not, the cradle placed on top of such barrels will lie in a skewed position. This can cause barrels to fall, leading to wine losses and injuries.
- The barrels should also be centred on the rack so that equal parts of the barrel ends extend over the rack on both sides. This will also ensure that the rack placed on top of the barrels lies even.
- If more than two layers of barrels are stacked on top of each other, care should be taken to ensure that the stack is 100% upright. This can be done by closely monitoring the stack from the front and sides. Forklift drivers stacking barrels do not necessarily perform this task, thus it is advisable to have a second person on the ground during stacking to check that everything is sound and so limit the risk of barrels falling over.
- Where there is only one barrel on a rack, the rack is unbalanced, with a high risk of falling over. The solution is to adjust about 3 – 5% of barrel racks in the cellar to be able to hold just one barrel right in the centre.
- The spacing between barrel stacks should be wide enough for a person to walk comfortably between the stacks. This simplifies the identification of barrels (the heads must be clearly visible), as well as sampling and stock control.
- Barrel stacks should not be stacked too high, as this can make it difficult to monitor barrels.
- The same principles apply to the storage of full, new and empty barrels.
Analyses and monitoring
Continuous testing of the wine is imperative to ensure that it ages as expected. Wine samples enable winemakers to detect changes in the wine’s aroma, flavour and texture, which in turn makes the timely identification of problems possible. Pay attention to the following:
- Samples should be taken at regular scheduled times during the maturation process, but the frequency may depend on the type of wine and the maturation goals. Most cellars perform analyses on their barrels monthly or every two months.
- If the batches are small enough, a sample can be drawn from each barrel. If the batches are larger, for example, 20 barrels in a batch, only half of the barrels can be sampled.
- Barrel analyses should always be compared to the analyses of the original tank they were filled from.
- The most important analyses that should be monitored are the free and total sulphur, as well as the volatile acidity. A few barrels per batch should also be tasted regularly, as analyses only tell one-half of the story. Wine faults (for example Brettanomyces) not tested for on routine basis can be noticed in this way. The sensory development of wine in the barrels should also be monitored.
- Detailed records of the barrel analyses, including sensory evaluations, should be kept. This allows winemakers to gain a better understanding of the wine’s development over time.
Drawing wine samples
The use of a curved stainless steel or glass wine thief is the most suitable method for drawing wine samples from a barrel. The opening on top of the wine thief is pressed shut while the wine thief is lowered into the wine in the barrel. By then lifting the finger from the opening, the wine will slowly fill the wine thief. As soon as it is full, take out the wine thief and carefully transfer the contents to the sample bottle.
If a composite sample has to be assembled, the sample should be taken as reductively and carefully as possible to avoid excessive oxygen uptake, which can cause a false reading on the free sulphur analysis.
Bungs
A well-sealed barrel ensures that the wine is protected against oxidation and contamination. It is important to inspect the condition of bungs regularly. Over time, bungs can become worn, causing the fit to be too tight or loose, which can have negative effects on the wine. Bungs should be replaced as needed to maintain the integrity of the maturation process.
Currently, there is a wide variety of bung closures available on the market. All of these come with their own set of advantages and disadvantages. There is even an electronic version (e-bung), which can send the temperature and volume of a barrel to a cellphone to warn if certain parameters are exceeded.
Temperature, humidity and CO2
Barrels must be spaced in such a way as to allow for good airflow around each barrel. This promotes the control of temperature, humidity and CO2 levels around the barrel.
The most acceptable barrel storage room temperatures for winemakers in South Africa are between 16 and 18°C. The temperature influences the maturation process of the wine, and temperatures lower than 16°C will result in slower development of the wine, whereas temperatures higher than 18°C will lead to higher losses and accelerated development. It is important to make sure that the temperature-control system is functioning properly on a regular basis (at least every other day). Especially after power outages, these systems tend to not restart and this can lead to a drastic increase in barrel storage room temperature.
The ideal humidity in a barrel storage room is between 75 and 85%. Anything lower will result in greater wine losses over time, and anything lower can promote fungal growth. To maintain an appropriate humidity, wine cellars must be equipped with humidifiers or moisture-control systems.
Keeping the doors of the barrel storage room shut as far as possible is very helpful in controlling the temperature and humidity effectively. If systems are not set up to regularly allow the inflow of fresh air from outside, it is a good practice to open the doors at least once per month for a while to allow entry of fresh air.
VERY IMPORTANT
If, however, there are barrels in the storage room undergoing malolactic fermentation (MLF), the control of carbon dioxide (CO2) is extremely important as high levels thereof can be life-threatening. The barrel storage room, in this case, should have very good ventilation, and the CO2 levels should be monitored with gas detectors. An alarm system should warn workers to leave the storage room immediately if CO2 levels rise beyond a safe concentration.
Barrel storage room hygiene
Hygiene is of utmost importance in the barrel storage room to prevent contamination by bacteria, wild yeasts and fungi, which can spoil the wines. Regular cleaning and sanitation of the storage room and barrels are essential. The whole storage room, including floors, walls and equipment, must be kept clean.
One of the best solutions to keep unwanted micro-organisms under control is to install a UV light behind the fans in the storage room. These lights can be connected to a time-controlled switch and, depending on the size of the storage room, can be switched on for a set period per day. There is also an option available of UV lights that produce ozone (O₃). The fact that the ozone gas can penetrate where the light is not necessarily able to makes this option very effective.
This same type of light can also be used to sterilise barrels, providing a fantastic alternative to burning sulphur strips in barrels. When sulphur strips are, however, burned, take care to ensure that the room is well ventilated and that staff wear the required PPE (personal protective equipment).
Conclusion
Each storage room aspect, from barrel stacking to the precise control of temperature, humidity and hygiene, plays a key role in upholding the quality of a wine. Maintaining a constant barrel storage room environment will ensure that the wines reach their full potential in the maturation process and develop the characters desired by the winemakers.
For more information, contact Pieter Badenhorst at pieterb@fortheloveofwine.co.za.
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