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WHAT'S UP IN THE VINEYARD AND CELLAR

The cleaning of tanks and barrels

by Charl Theron

Cellar sanitation is a prerequisite for the vinification of healthy, quality wines. Not surprisingly there is often a correlation between the visual appearance of a cellar and the quality of its wines. As with most cleaning processes, water is the cleaning aid most used in cellars. The amount of water and cleaning aids used impacts not only on the cleaning process, but also plays a decisive role in the volume and quality of the cellar’s waste water. Different methods should therefore be compared from point of view effectiveness.

The best time to clean tanks and barrels is immediately once they have been emptied and the process usually consists of the removal of solids from the container, an alkaline washing process to remove the tartrates, followed by an acid solution to neutralise the alkali and eventually a rinse with water to neutralise the container before being used again. The solids to be removed usually include skins, pips, yeast and fining residue, but the tartrates can only be removed with the alkaline solution. The alkaline washing process also kills a wide range of spoilage organisms, which can also to a certain extent be achieved by the subsequent acid solution.

The following equipment is required to facilitate an effective wash process:

  • Safety goggles.
  • Rubber gloves.
  • Rubber shoes.
  • Wet hat and - suit.
  • An eye washing facility, or portable eye wash solutions.
  • Acid and alkaline washing aids.
  • A pump for warm liquid and the washing aids in question.
  • Food grade quality pipes that are resistant to the washing aids.
  • pH meter.
  • Safety information for the cleaning aids being used.
  • Sufficient portable lights.
  • A spray ball if the tank is to be washed from the outside.
The cleaning process can be divided into the following stages:
  1. The removal of all solids from the container.
  2. Ensure that all safety clothing and equipment are in place before commencing the washing process.
  3. Dismantle all container valves, fittings and attachments that are easily removed and rinse with water. Leave to soak in an alkaline solution. Remove the ports to clean all parts properly.
  4. Clean all parts with a brush to ensure that all fixed solids are removed. This is particularly relevant to parts that are fixed with wire.
  5. Rinse the container and the parts with water to remove all solids.
  6. If cleaning the container from the outside with a spray ball, sufficient water (approximately 5% of the container capacity) should be pumped into it and the water pumped from the bottom of the tank via the spray ball to ensure sufficient water distribution. Cover the opening of the tank so that the water does not splash out. Circulate the water and make sure of splash threats before using chemicals.
  7. The strength of the alkaline washing aid that is subsequently used should comply with the product’s prescriptions and is always mixed in a bucket or barrel outside the container, before being used inside the tank. Ensure that the necessary safety precautions are taken throughout the entire process. Take care to avoid possible splashes during the circulation of the alkaline washing aid, which may take 20 to 30 minutes.
  8. Once circulation has been completed, leave for 5 minutes to drip dry, before inspecting the tank to check whether all the tartaric acid has been removed. If not, it should be readjusted to the original pH through the addition of more alkaline washing aid. If the alkaline washing process has been thorough, disposal thereof should take place in the correct way.
  9. An acid solution (0,6% citric acid, although from an environmentally friendly point of view it is better to use anorganic acids, such as phosphoric acid or nitric acid) should then be circulated to neutralise the alkaline washing process. This should take approximately 5 minutes. Thereafter the wash water should no longer feel soapy and its pH should be below 5.5. If not, more citric acid should be added to the rinse water. Allow the wash water to drip dry and do a final rinse with clean water.
  10. The tank fittings that are soaked in the alkaline washing aid are rinsed with an acid solution and water, in the same way as the tank, before being replaced.
  11. Once the washing process of a tank is completed, it should be indicated thus on the tank records. Containers should in all instances be rinsed with water, before being used again (Payette, 2007).
In the case of barrels, however, other control actions besides the washing process should be undertaken. In the case of barrels, chlorinated water should never be used, as this could result in the formation of undesirable anisols. It is generally also better to keep barrels filled and monitored on a monthly basis.

New barrels can be handled in different ways. They may be filled with wine immediately without any treatment, but this practice is not recommended because barrel leakages may occur, unless a pressure test is done before filling. They may also be rinsed quickly before being used, but this has the same disadvantages as the previous method. Alternatively barrels can be filled with 50 to 75 litres of water, before being left on the two heads for 12 to 24 hours to allow the wood to swell. The more cumbersome, but safest method, is to fill the barrels with cold or warm (50°C) water and leave them for 24 to 48 hours before being used. It is expedient to use a citric acid solution (pH 3.5 or lower) and sulphur dioxide solution (60 to 70 mg/l) to prevent the water from deteriorating.

Barrels that have been emptied, should receive attention as quickly as possible, unless they are used again immediately after rinsing. The bung area of barrels especially should receive intensive attention. If barrels are not reused immediately, however, they should receive additional attention, besides the washing process. Various forms of sulphur dioxide treatment may be applied. Liquid sulphur dioxide (10 grams per 225 litre barrel) may be followed by a monthly treatment (5 grams per 225 litre barrel), but the addition should preferably take place in the open air. Candlewicks may also be burnt (most sulphur wicks contain 6 grams of sulphur dioxide) or sulphur dioxide tablets may be used. Barrels should preferably be stored at 10°C in the shade under mould-free conditions and not be exposed to large temperature fluctuations.

Various rinse aids can be used for barrels. Chlorine free water with sufficient pressure to remove solids is preferable. Ozone is increasingly popular, but should be used with circumspection and only in well-ventilated environments (Payette, 2008).

References

Payette, Tom. 2007. How to Clean a Wine Tank. Vineyard & Winery Management, January/February 2007: 96 - 100.
Payette, Tom. 2008. Barrel Care. Vineyard & Winery Management, July/August 2008: 99 - 1001.

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