How long does vodka keep after opening?

An opened bottle of vodka stays good for years and there is no legal period within which you must finish it.

Vodka contains, according to the European regulation for spirit drinks, at least 37.5 percent alcohol. At that strength bacteria and yeasts get no chance. Nothing grows in the bottle, nothing goes mouldy and the drink does not turn sour, even if it has been in the cupboard for two years.

What does happen is a slow change in aroma and flavour. The emptier the bottle, the more air in it and the faster this goes. With vodka you notice little of it in practice, because vodka is built precisely on a neutral character. If you finish the bottle within a few years, there is nothing to worry about.

Drinks with ten or more percent alcohol by volume do not need to carry a minimum durability date in the European Union.

That exception is in the regulation on food information to consumers, Regulation (EU) 1169/2011, in Annex X. At at least 37.5 percent, vodka is well above that limit. So you will not find a best-before statement on a bottle of vodka. That is no negligence on the part of the producer and says nothing about the age of the bottle.

What you do find on the label is the alcohol content by volume, the contents and the legal name of the drink. If there is a batch or lot number on the bottle or on the cap, it refers to the bottling run and not to a shelf-life limit.

In this bottle, alcohol itself is the preservative, and vodka legally contains at least 37.5 percent of it.

Vodka is made from ethyl alcohol of agricultural origin. According to the same regulation, that alcohol must be at least 96.0 percent before water is added, and it is distilled from agricultural raw materials, classically potatoes or grains. There is otherwise almost nothing in the bottle: no dairy, no fruit pulp, no significant sugar. It is precisely this simplicity that makes vodka stable, because nothing is present that can ferment or rot.

Research into spirits shows that alcohol content and storage temperature do have a measurable effect on stability. In a study in the trade journal Foods, distillates of 40, 50 and 70 percent were stored in the dark for eight weeks at minus 18, 0, 8 and 20 degrees. A lower alcohol content and a lower temperature produced more haze, and the composition of the volatile compounds shifted with the temperature. Neither had a demonstrable effect on the methanol content.

The aroma and flavour of vodka slowly become flatter in a bottle that is half empty and has stood open for years, because alcohol and volatile substances disappear into the air above the drink.

The more air there is above the vodka, the larger the surface on which that happens. A bottle that is still three-quarters full keeps better than a dribble that has been standing in the cabinet for a year. If you screw the cap on firmly after each use, you limit that loss considerably. This works better with a screw cap than with a cork that no longer closes properly.

Heat speeds up the process. That is why we do not place spirits in the sun or near a heat source in the shop, and we advise the same at home. With flavoured vodka the loss is noticed sooner than with neutral vodka, because there is more aroma in it that can disappear. If you doubt an old bottle, smell it first and try a tiny bit.

Vodka mixed with cream, eggs or fruit juice is no longer vodka in the legal sense and often has a lower alcohol content, so spoilage after opening is possible.

Flavoured vodka is something different. It is a category of its own in Annex I of the regulation, with the same minimum of 37.5 percent alcohol. Such a bottle is therefore just as stable as neutral vodka. Only the added flavour fades faster, so it is best to finish that bottle within a year or two.

It is different with vodka-based liqueurs. According to the regulation, a spirit drink only needs 15 percent alcohol, and cream or egg liqueurs are often around that level. Such bottles carry storage advice, and that is not non-binding text: Regulation (EU) 1169/2011 prescribes in Article 25 that storage instructions and, where necessary, a use-by date after opening of the packaging must be stated. In that case, always follow what the manufacturer puts on the bottle, and put it in the fridge after opening if it says so.