In the picturesque vineyards of France, brandy producers in Cognac have long set the gold standard for what to use as their base input. Namely, wine that hasn’t had sulphur added to it.
But what if your wine does contain sulphur? Is all hope lost for distilling a palatable brandy or vodka made from grapes, or can something be done?
While it’s certainly not ideal, it’s not a lost cause either.
This article takes a nerdy dive into the science, process, and equipment needed to remove sulphur from fermented wine before distillation.
The sulphur quandary
Wine often gets sulphur dioxide (SO2) added as a preservative. It serves several purposes in wine production. Mainly it acts as preservative to prevent spoilage and oxidation, thereby helping to maintain the wine’s freshness, flavour and longevity.
The science of it is relatively simple. A portion of the SO2 interacts with various components present in the wine, binding to them and thereby becoming inert as both an antioxidant and an antimicrobial agent.
The residual SO2 exists in two forms: bisulphite (HSO3_) and molecular SO2. It’s this SO2 – the sulphur dioxide – that is particularly effective against undesirable microorganisms and bacteria.
While sulphur is beneficial for winemaking, it’s problematic for distillers who aim to produce brandy, or distil vodka from a grape base.
This is because during distillation, it’s not just the alcohol but also the sulphur that gets concentrated. And when sulphur levels breach the taste threshold, the resultant brandy can taste like rocket fuel – literally undrinkable. Depending on the concentration of it, it might as well be used for that given how harmful it can be too…
To go back to the gold standard in brandy making – there’s a reason why Cognac distillation centres around Ugni Blanc grapes and is restricted to a specific time frame each year. Distilling season is from the onset of harvests – typically in October – until March 31st of the subsequent year. It is a way of creating a focus on natural preservation by producing wine with higher acidity and by having the distillation season occur during the cooler months.
Sulphur and sulphites explained
Sulphites, alternatively spelled “sulfites”, are inorganic salts often utilized as food additives.
They exist naturally in many items, from our bodies to various foods – for example raisins, apricots, and prunes. Many foods have sulphite concentrations up to ten times greater than what’s typically found in wines.
In the European Union, sulphites are classified as food additives and are subject to specific regulations. Any product containing more than 10 parts per million (ppm) of sulphites, or 10 milligrams per kilogram or litre, is required to clearly state “contains sulphite” on its label. These sulphites are also identifiable on packaging through their E-numbers, which range from E220 to E228.
It’s worth noting that every type of wine, irrespective of additional sulphites having been added or not, contains them. Even organic wines are not sulphite-free. EU standards allow the addition of sulphites in organic wines, all be it in smaller quantities than in non-organic wines.
Additions of sulphur dioxide can occur at multiple points during the wine-making process. It can happen while the grapes are in the vines, through the use of pesticides, sprays and more. It’s most commonly added through the use of liquid SO2 solutions (or sometimes sodium or potassium metabisulphite) once the ferment is over.
In the concentrations typically found, sulphur is not the enemy for a wine maker or wine drinker. They should not be seen as a negative. In many ways, the entire industry is reliant on them to ensure consumers have great products on a consistent basis.
The issue comes in what the distiller wants and needs to do next – concentrate wine through the act of distilling. It’s at that point that it’s problematic.
Sulphur Removal
We now know that sulphur becomes concentrated in the distillation process and that high levels of sulphur can make the distillate taste unpleasant (and potentially unsafe). So how can it be removed?
Copper can act as a sulphurising agent but not to the point where a wine will be freed of the SO2 it has. You need to actively remove it before distillation.
Unfortunately, all removal methods will also affect the ester levels in your spirits (read, it will affect flavour). There is no way of removing SO2 without also reducing the quality of the wine. It’s a case of compromising and finding the right balance.
With that said, it’s generally accepted that the hydrogen peroxide method alters the ester content the least.
Using the Hydrogen Peroxide method
Hydrogen peroxide (H2O2) is an oxidising agent capable of decreasing SO2 levels, and relatively simple to work with.
Hydrogen peroxide should be diluted below 1% concentration before use. This mitigates the risk of over oxidation. After slow addition, the wine should be stabilised for several hours before confirming the reduced SO2 levels through analysis.
Below are the steps:
- Measure the wine quantity.
- Consult your wine supplier to determine the exact sulphur content.
- Calculate the total amount of sulphur.
- Slowly add the appropriate amount of hydrogen peroxide.
- Let the wine sit overnight with an open lid.
- Proceed to distil the treated wine.
Because the sulphur has been reduced, the distilled product will be of higher quality.
Other treatments include Calcium Oxide & Activated Carbon
In a similar process to H2O2, Calcium oxide can be used to reduce both acidity and total SO2. Meanwhile, it’s possible to run either the wine through activated carbon or the distillate that’s been made. The carbon strips out significant quantities of SO2 – but it will also reduce the over flavours too.
It’s possible to do a combination of these techniques too.
For example, a Vodka maker may chose to find the best priced bulk wine supply rather than seasonally available sulphur free supplies, use Hydrogen Peroxide to reduce sulphur levels, distil safely without having to deal with high SO2 levels (which smell really bad, make the distiller’s life a misery and corrode stills quickly) – then also run the distillate through a carbon filter. This would be a good way to make a neutral tasting product that has the underlying properties of the grape base. In this case, the loss of flavour is acceptable, as the aim is to be relatively neutral.
Best case scenario
It’s clear that the best-case scenario is to start with a wine that hasn’t had sulphur added. But it is entirely feasible to work with wines that do if you are willing to accept the compromises.
For those seeking that best case, best result situation – understand that when winemakers opt not to add SO2 to their production process, they are foregoing its valuable benefits. Specifically, the wine becomes more susceptible to oxidative damage and microbial spoilage.
Therefore, distillers desiring SO2-free wine must liaise closely with their winemakers before harvest, and align their production schedules. They should be primed to act promptly upon the wine’s readiness.
Tips and tricks for those working with sulphur free –
Ullage (the amount by which a container falls short of being full) must be carefully managed as the wine in tanks is drawn down on.
A simple and effective trick is topping up wine tanks with either nitrogen or a combination of argon and CO2 gases at a proportion of 80:20 respectively. This blend is heavy, moving down the tank as the wine gets depleted, and hence requires only a thin layer.
Depending on the region and the grape varietals, altering the acidity levels of the wine might be possible. This can be done by adding citric or tartaric acid. While it would increase the wine’s acidity before distillation, it would also add to the cost due to the large quantities needed. But it’s a trade off worth considering for some.
There will never be a perfect way to preserve wine and avoid all issues ahead of distillation. But by looking at it holistically, those who buy sulphur free wine can dramatically increase the window in which they can operate in.
Use quality grapes, have a quality fermentation that’s controlled at the correct temperatures, ensure the ullage in tanks is managed and if possible additional safeguarding through installation of a cooling system to keep the wine chilled. All of these things help mitigate against oxidisation and bacterial risk.
Working without sulphur and in a preventative, seasonal way gives you a far better chance to produce the highest possible quality eau de vie from wine than any removal method could. It’s far better to start with quality and accept limitations than compromise before you’ve even begun distilling.
A complex but achievable task
Sulphur removal in brandy distillation, especially from sulphur-treated wines, is a complex but achievable task.
Using methods like hydrogen peroxide treatment and activated carbon filtration, distillers can effectively reduce sulphur levels, though it may impact the wine’s ester profile. Ideally, starting with sulphur-free wine is preferable, yet working with sulphur-treated wines is feasible with careful management.
Ultimately, it’s a case of balancing the challenges of sulphur removal with the preservation of the wine’s inherent qualities.
