About a year ago I did a vanilla extract tasting to test out different types of vanilla beans, as well as compare commercial to homemade. To refine the quality of homemade extracts, I wanted to test out how different alcohols affected the flavour of the final extract. So I prepared four extracts using the same beans and proportions, with the alcohol solvents being bourbon, Calvados (apple brandy), rum, and vodka. The first three are all wood-aged but come from different sources (grain, fruit, and sugarcane respectively); while vodka is not wood-aged and usually doesn't have character deriving from its original ferrmentable component.
What was surprising about this tasting was that the type of alcohol made very little difference. Compared side to side, the wood-aged alcohols had a touch more complexity (actually, the term that I used in my notes was "round"), while the Calvados and vodka exposed more floral character. The bourbon had the most of that "round" flavour which suggests that indeed comes from the wood, as I find bourbon to be especially woody compared to other spirits. The vodka I initially described as "woodsy" which is funny since it's the one without a wood component, so I theorized that what I described as woodsy was the plainness or lack of roundness brought by the (aged) wood in the other alcohols. The Calvados one struck me as pleasantly "citrusy" in a way that the others didn't; I didn't include a grape brandy in the lineup but wonder if it would have had the same effect due to the fruit notes of the alcohol.
These differences were quite subtle though, and in real-world applications I think would disappear entirely. Therefore I conclude that the type of alcohol is not very important in making vanilla extract. That said, I did find the Calvados my top pick for the citrusy and floral aspects, the floral in the vodka also making it preferred, and the wood-aged ones in general adding a good "round" flavour. Therefore for future extract runs I might prefer an aged fruit brandy as the extraction medium, and at least a wood-aged alcohol or subsequent aging in wood if that's an option.
Here are the notes I took on the 4 extracts I tested, in descending order of preference:
- Calvados: slight citrusy / floral.
- Vodka: slight woodsy, also the floral.
- Bourbon: the most round, more vanilla but less other complexity.
- Rum: good basic vanilla, round.