A Technical Guide for Wine Producers

RECENT ARTICLES   |   WYNBOER HOME WHAT'S UP IN THE VINEYARD AND CELLAR Different barrel washers by Charl Theron Barrels are washed for two particular reasons. The pore structure of barrels serves as a highly suitable habitat for micro-organisms and the effective washing of barrels is extremely important to ensure the desired barrel hygiene. To make certain that the wine remains in contact with the wood surface, deposits such as colour or tartaric acid crystals, must also be removed during the washing of the barrels. The high capital cost of wood barrels induces cellars to follow best practices for barrel washing, so as to ensure the most effective use of the barrels. The use of chemicals has become unpopular with winemakers, who place a priority on wood integrity. Peroxide products that degrade spontaneously after application may be the exception to the rule. Barrel washers usually consist of a rotating spray head placed inside the barrel through the bung hole. Spray heads, detergents and washing conditions, for example temperature, differ and the various combinations thereof have to be taken into account when winemakers make certain decisions. Depending on the size and requirements of the cellar, a decision should be taken regarding the amount to be spent on barrel washing equipment. The throughput tempo of the equipment is a determining cost factor. Some washing equipment also requires additional equipment, such as heating of water and ozone supply, which should be taken into account. The basic goal of different barrel washers remains the cleaning of barrels, but the amount of mechanisation plays a significant role in the equipment on offer. The position of the spray head in the barrel also plays an important role and there are various options in this regard: The simplest and cheapest system is the so-called "peg leg" system in which a tripod or quadripod stand supports the spray head. It has been designed to wash a barrel with the bung hole pointing downwards, which means that manual labour is required to turn the barrel, place the spray head inside the barrel and switch on the washing process. As a result of the position of the bung hole, the wash water will drain from the barrel by itself. A vacuum condition may also be created inside the barrel to remove the wash water from the barrel without the bung hole being directed downwards, but the amount of water injected into the barrel must be the same as that which is removed from the barrel in order to prevent accumulation of water in the barrel. So-called "hand-truck" washers have the barrel positioned on a roller, which makes it possible to rotate the barrel so that the spray head may be positioned through the bung hole from the side. After the wash process the barrel may then be rotated to turn the bung hole downwards and the wash water will drain from the barrel. Semi-automatic and automatic equipment make it possible to remove barrels mechanically from stacks, place them on rollers for rotation and apply a wash cycle. Such equipment will obviously be expensive and can only be justified by large cellars. The temperature of the water used by barrel washers plays a very important role. The removal of tartaric acid from barrels, for example, requires a temperature of 60 to 80°C, while it also plays an important role in the sanitation of barrels. As a result of the porosity of wood, barrels present a very suitable growth environment for undesirable microbes and moreover, wood is a good isolator and consequently a poor conductor of heat. From a practical point of view, it is therefore difficult to obtain effective sanitation in the wood. A distinction should be made between the sanitation and sterilisation of barrels. For example, if Brettanomyces is said to be killed at 80°C, one should also realise that this is only possible if that temperature is maintained for 30 minutes, an impractical option considering the above-mentioned characteristics of wood. Higher temperatures such as 100°C are undesirable as they may result in off-flavours in the wine. The use of steam is also an option. In addition to the high temperature of such treatment, a vacuum in the barrels, which is created by the cooling process, will be closed following the steam treatment, thereby extracting wine residue from the pores. The energy cost to achieve the specific temperature of the process is also a significant consideration. The pressure and flow tempo is another important physical factor when washing barrels. The pressure during treatment ranges from 60 to 1 500 psi in different washing equipment, while the flow tempo ranges from 13.5 to 36 litres a minute. These two factors play an important role in the wash action of some spray heads and cellars will have to decide which specifications are preferable depending on their requirements. The effective removal of tartaric acid requires high pressure and temperature, for example. From a cost point of view the water consumption of the various systems will also have to be compared. The possible use of ozone when washing barrels should also be considered. It is effective for sanitation but not for cleaning, which means that barrels must be cleaned sufficiently before using ozone. Ozone may be an irritant and should be handled as a hazardous agent. In order to penetrate the wood, it should preferably be used in gas format. Due to the cost involved, it is usually not an option for small cellars. More information may be obtained on the websites www.sustainablewinegrowing.org or www.pge.com. Reference Pregler, Bill. 2007. Product Review: Barrel Washers. Wine Business Monthly, May 2007: 34 - 39.

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