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Winery cleaning: why hygiene is part of wine quality

A perfectly clean winery is not simply a tidier one. Above all, it is an environment in which it is easier to control what happens to the wine. During winemaking, surfaces, pipes, tanks, pumps, floors and equipment continuously come into contact with must, wine, yeasts and organic residues. Sugars, nitrogen compounds and other substances can accumulate on surfaces and create favourable conditions for microbial growth. Some microorganisms are essential to wine production, while others can become a problem.

For this reason, cleaning cannot be considered an activity to be carried out only at the end of the work. It is part of the production process and accompanies practically every stage, from grape reception through to bottling. Nor does it mean pursuing absolute sterility, which is often unrealistic and unnecessary in a winery. Rather, it means understanding the possible risks, removing residues before they become difficult to eliminate and keeping microorganisms under control in those areas where they could compromise the product.

Cleaning does not simply mean removing dirt

A surface may look clean without being clean enough: it is important to distinguish between cleaning and sanitisation. Cleaning is used to remove visible residues and deposits: traces of must and wine, sugars, organic matter, scale and other compounds that can adhere to surfaces. Sanitisation, on the other hand, acts on the presence of microorganisms and aims to reduce them to levels compatible with the production process.

Another important aspect is the order of operations. A sanitising product does not replace proper cleaning: if organic residues remain on the surface, its effectiveness may decrease. First the dirt is removed, then the microbial load is addressed when the process requires it. A working cycle may include an initial rinse to remove the coarsest residues, the use of a detergent suitable for the deposit to be removed, a subsequent rinse and sanitisation. However, there is no single procedure that is identical for every situation. The result depends on the product used, its concentration, temperature, contact time, the mechanical action applied during washing and, above all, the nature of the dirt and the surface.

Third point: which detergents should be used? Alkaline products are mainly used against many organic residues. Acid treatments may be necessary for mineral deposits and scale, including those related to tartrates. For sanitisation, specific products can be used, including formulations based on peracetic acid or hydrogen peroxide, always in accordance with the manufacturer’s instructions and with the compatibility of materials and systems. In other situations, hot water or steam may be used.

An interesting case concerns chlorine. In many environments it is almost automatically associated with disinfection, but in a winery its use requires particular attention. Chlorine-containing compounds can contribute to the formation of chlorophenols and, through subsequent microbial transformations, chloroanisoles. These include TCA, one of the molecules associated with the well-known defect commonly referred to as cork taint. For this reason, several oenological protocols tend to avoid chlorinated products in areas and on equipment that may come into contact with wine or with porous materials.

When residues become a problem for wine

Must and wine are biologically active environments. During production, yeasts and bacteria come into play that may be desirable at some stages and undesirable at others. Leaving residues on equipment means providing them with surfaces to adhere to and, under certain conditions, multiply. The problem becomes more complex when a biofilm forms. This term refers to a community of microorganisms attached to a surface and enclosed within a matrix that the microorganisms themselves help to produce. It is not simply dirt. Once formed, a biofilm can be more difficult to remove and can give microorganisms greater protection against normal treatments. Pipes, fittings, seals, valves and hard-to-reach points therefore deserve particular attention. A small residue left in an inaccessible area can become a source of contamination for a subsequent production process.

The consequences are not necessarily immediate or dramatic. More often, they appear as anomalies that become difficult to trace back to a single cause: less controllable fermentations, aromatic alterations, unexpected variations, contamination between batches or reduced product stability. Among the best-known microorganisms in winemaking is, for example, Brettanomyces, a yeast capable of producing volatile compounds that, above certain concentrations, can significantly alter the aromatic profile of wine. Some acetic acid bacteria or lactic acid bacteria can also become problematic when they develop at the wrong time or in the wrong environment. This does not mean turning the winery into an environment completely free of microbial life. That would be a contradiction for a product that exists precisely thanks to the activity of microorganisms. The point is to manage this presence, preventing residues and contaminated surfaces from introducing unwanted variables into the process.

Regular cleaning also helps avoid another very practical difficulty: time. Fresh residue is normally easier to remove than a deposit left to dry for hours or days. Delaying washing can mean having to use longer treatment times, more mechanical action or more intensive procedures later on. In this sense, good hygiene is also a matter of work organisation.

How to clean stainless steel, pipes, floors and barrels

The variety of materials found in a winery makes it impossible to think of a single treatment that works for everything. Stainless steel, widely used in tanks and winemaking equipment, provides a resistant surface that is relatively easy to clean if kept in good condition. Even in this case, however, compatible products must be used and attention must be paid to scratches, welds, joints and areas where residues can accumulate. Pipes and fittings present a different problem: much of the surface to be cleaned is not visible. The correct circulation of cleaning solutions, their ability to reach every part of the system and the absence of areas where liquid can stagnate therefore become essential. Seals and flexible components also require attention. In addition to cleaning, their condition matters: a deteriorated, cracked or worn surface is more difficult to keep hygienically clean.

Then there is wood: a porous material into which microorganisms can penetrate, making both cleaning and sanitisation more complex. A contaminated barrel can become a persistent source of unwanted microorganisms over time. This is also why maintenance, washing and correct barrel management require specific procedures. Floors and drains may seem more distant from the wine, but they are not secondary elements of hygiene management. Residues, stagnant liquid and moisture can encourage microbial growth, attract pests and increase the risk of indirect contamination. There is also a very practical aspect: must and liquids left on the floor can make surfaces slippery and create safety problems for people working in the winery.

A good cleaning procedure must bring all these aspects together. It is not enough to establish what to use: it is necessary to define when to intervene, how often, at what concentrations and for how long. It is equally important to check that the system is working, periodically inspecting the condition of surfaces and, where necessary, carrying out microbiological checks. Winery hygiene is above all about continuity. Not large occasional interventions, but correct operations repeated at the right time. This is also why cleaning affects wine quality long before the wine reaches the glass. Removing a deposit, washing a pipe correctly or intervening immediately after a process may seem like actions far removed from the final result. In reality, they help reduce the variables that the producer does not want to find in the process.

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