Why does one vodka taste different from another?

Vodka may be sweetened up to at most 8 grams of sugar products per litre, expressed as invert sugar.

The regulation calls this rounding off the taste. Eight grams per litre is little compared with a liqueur, but enough to make the finish softer. Stating it on the label is not mandatory.

During distillation, the characteristics of the raw material and the by-products of fermentation are selectively weakened.

That is how it is set out in category 15 of Annex I to Regulation (EU) 2019/787. The further a maker takes that step, the more neutral the distillate becomes. The regulation also allows additional distillation and treatment with suitable processing aids. Where one stops at a light touch, another goes on until almost nothing of the raw material remains.

For vodka the methanol content may be at most 10 grams per hectolitre of 100 percent alcohol.

For ethyl alcohol from agricultural products in general that limit is 30 grams. The stricter requirement suits the character of the category: a drink in which the traces of raw material and fermentation have deliberately been reduced. It is an upper limit, not a target value; how much is actually in it differs per maker.

The rules allow additional distillation and treatment with suitable processing aids, including activated carbon.

Filtering over charcoal removes substances that are still in the drink after distilling. One maker filters once, another several times or over other material. The regulation sets no requirements for the number of filtering steps, so that number on a bottle is not a legal measure.

Only natural flavourings or flavouring preparations that are present in the distillate of the fermented raw material may be added.

That leaves little room for flavourings. Vodka with a clear taste of lemon, caramel or pepper falls under flavoured vodka, a separate group with its own designation. On the shelf they often stand next to each other, but the rules differ.

In a study of 45 samples of raw spirit, rye, wheat, maize, potato and sorghum could be told apart by their volatile compounds.

The study looked at spirit before rectification, using two-dimensional gas chromatography and mass spectrometry. All samples were classified correctly. How much of that difference remains in the bottle depends on how far rectification and filtering have been taken.