Equipment Hygiene in the Winery

When is it too much—or too little?

Hygiene is co-responsible for wine quality, yet it is often either underestimated or overestimated. The key is understanding your objective and having the knowledge to decide when, how, and what to clean.

Cleaning is the most time-consuming operation in wineries without automation. At the same time, it must be managed with financial and environmental sustainability in mind—overdoing it is neither efficient nor responsible. Hygiene operations also expose workers to potentially hazardous situations, making proper training essential.

Key considerations

• Clean or sanitised?

• Production status

• Wine type

Clean or sanitised?

Sometimes “clean” is sufficient; at other times, sanitisation is required.

Cleaning refers to the removal of extraneous material—organic or inorganic—from a surface. Sanitisation, by contrast, aims to eliminate potentially harmful microorganisms, either through physical removal (for example, sterile filtration) or chemical disinfection (killing).

A crucial point to understand is that most cleaning agents are not sanitisers, and most sanitisers are not effective cleaners. While some products or processes can perform both functions, my preference is to separate cleaning and sanitisation based on need, allowing for more precise and sustainable interventions.

One fundamental principle must always be respected: if sanitisation is required, cleaning must come first. Sanitisers are ineffective on dirty surfaces, as organic residues and tartrates provide both shelter and protection for microorganisms.

A simple comparison illustrates this clearly. Sodium hydroxide (caustic soda) behaves much like a strong soap: it dissolves and removes organic matter but has no direct disinfectant action. However, with thorough rinsing, it can still physically remove microorganisms.

Peracetic acid, on the other hand, is primarily a disinfectant, with little detergent capacity. In general, alkaline substances are best suited for cleaning, while oxidising agents—such as peracetic acid, ozone, heat (steam or hot water)—are sanitisers. Their effectiveness is significantly enhanced by time and mechanical action, such as pressure.

Production status

At harvest, grapes are naturally covered with yeasts and bacteria. The most effective control strategy at this stage is rapid yeast inoculation, allowing the desired population to dominate and suppress unwanted microorganisms. Under these conditions, sanitisation is not required—cleaning alone is sufficient—as alcoholic fermentation begins promptly. However, if past biological deviations are known, sanitisation is strongly recommended.

Once juice becomes wine—once alcohol is present—and residual sugar is depleted, sanitisation is again generally unnecessary, provided there is an adequate level of molecular SO₂. Exceptions include sweet wines, high-pH wines, or stuck fermentations with microbiological deviations.

During storage in tanks or barrels, regular tasting is essential. Experienced winemakers can detect deviations at an early stage and intervene accordingly. This vigilance is particularly important for low-intervention, organic, and “natural” wines, which are inherently more vulnerable.

In my view, sanitisation is truly mandatory only during bottling and disgorging. In all other phases, it depends on conditions. That said, I recommend sanitising all equipment at least once a year to keep microbial populations under control while avoiding resistance that can arise from excessive or routine sanitisation. It is equally important to understand the “blind spots” of tools and equipment, where microorganisms may persist unnoticed.

Wine type

Different wines require different hygiene strategies, largely determined by alcohol content, residual sugar, malic acid, pH, and—critically—the intended style and expectations of the final product. Below is a brief outline of how I generally approach different wine types:

Fortified wines (≥18% alcohol)

Where oxidation is part of the wine’s character, I never sanitise, use no SO₂, and do not apply sterile filtration.

Still and sparkling wines (dry, post-MLF)

Base wines without residual sugar that have undergone malolactic fermentation, with pH < 3.6 and a stable 0.8–1.0 ppm of molecular SO₂, generally do not require sterile filtration or sanitisation.

Dry wines and sparkling bases (low pH)

Wines with pH < 3.2, even in the presence of malic acid, and with stable molecular SO₂ at 0.8–1.0 ppm, do not require sterile filtration or a highly sanitised environment. Wines destined for secondary fermentation should not exceed 0.6 ppm of molecular SO₂, depending on the yeast strain used and the timing.

Nothing in winemaking is black and white. When I say that certain wines “do not need” sterile filtration or sanitisation, I mean that they are generally in a safe zone. Every decision carries risk, and that risk must be consciously incorporated into the overall management strategy.

Knowing the wine you are working with is the foundation of any winemaking plan. Of the seven countries in which I have worked, the UK—thanks to its cool climate and naturally low pH—is the country where sanitisation is least often required.