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Nearly every recipe for making vanilla extract suggests the use of Vodka, or an alternative alcoholic beverage with a high alcohol content (typically 35%+), such as Rum or Bourbon. However, the various recipes typically default to Vodka for its more neutral taste. Essentially, the recipes simply instruct to leave opened vanilla pods in the alcoholic beverage for at least several months. The high alcohol percentage is required for the vanilla flavour to diffuse over time.

This made me wonder why I cannot find a single recipe that simply recommends the use of pure food grade ethanol, like that used to make Limoncello or other fruit- or herb-based liquors. It is typically cheaper, does not add additional flavour, and its high alcohol percentage (typically 95%+) (Rectified spirit) should suggest a better diffusion of flavours, or not? What am I missing?

Basil Bourque
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JJM Driessen
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    Do note that commercial vanilla extract is extracted under pressure, so the homemade version can never be more than around 1/3 as potent. – FuzzyChef Aug 08 '23 at 19:06
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    It's worth noting that you are very unlikely to find _pure_ alcohol. Alcohol/water mixtures form an [_Azeotrope_](https://en.wikipedia.org/wiki/Azeotrope). Getting past about 95 or 96% alcohol (by weight) is very difficult (and often involves using other compounds) – Flydog57 Aug 09 '23 at 17:26
  • @Flydog57 and if you do manage to get anhydrous alcohol and leave the container open you'll be back to 95% in no time. – Chris H Aug 11 '23 at 14:27

2 Answers2

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I can see two possibilities.

One is that vodka and the like are highly available. You can buy them in almost any country, and in most places just in a supermarket. They're even fairly likely to be on the shelf at home - I made vanilla extract using rum that I'd had for ages, when the covid home-baking boom meant vanilla extract sold out in my local supermarkets.

Pure high-proof alcohol is only cheaper if you're going to use it all in flambéeing, making extracts, etc. - you're not going to drink up the leftovers. At least here in the UK, spirits are taxed by the amount of ethanol you're buying. So a bottle of 80% ABV would attract twice as much tax as a the same size bottle of 40%. That means the pure stuff is going to look very expensive, which will go some way towards explaining its limited availability - and specialist retailers aren't cheap.

But there's reason another too. We use true vanilla extract because it's a more complex flavour than its main component vanillin. Vanillin is far more soluble in alcohol than in water, but the other compounds that contribute to a natural vanilla flavour may not all be. In that case you'd actually want a decent amount of water to extract these other compounds.

After all, even industrially, when pure ethanol is a readily-available ingredient, a water-ethanol mix is used for the extraction (see, for example, this patent), rather than extracting into ethanol and then diluting for sale.

Chris H
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    The first argument might be a territorial issue. For me personally, I can buy 96% alcohol from the supermarket across the street @ €20/1L (e.g. see https://www.carrefour.it/s/carrefour-IT/p/torriani-alcool-buongusto-96%C2%B0-100-cl/8001500010409.html?). It is approximately double the price of the cheapest Vodka per liter, but per liter of alcohol it is actually still cheaper. As such, if you would dilute with water to get <50%, the pure alcohol is cheaper. The second argument is interesting, I will look further into it in the hope to find a desired (range of) alcohol percentage. – JJM Driessen Aug 08 '23 at 12:20
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    @JJMDriessen Yes, in many places, 190+-proof alcohol is either difficult and expensive to procure, or outright illegal. – Sneftel Aug 08 '23 at 13:12
  • @JJMDriessen It's very hard to find in the UK. I've also failed to find it in a big supermarket in France (when I wanted to bring some home for similar experiments). I could order food grade 95% extraction alcohol for a similar price to what you pay, plus delivery (which probably isn't cheap - it isn't on other flammable liquids). – Chris H Aug 08 '23 at 13:41
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    From my understanding of chemistry it would seem very odd if some substance is soluble well in water but not in alcohol. Chemically alcohol is a universal solvant where both water soluble and fat soluble substances can disolve. – quarague Aug 08 '23 at 14:16
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    @quarague Agreed. And food grade ethanol would *always* be mixed with ~5% water, because it's impractical to purify it past that point. – Sneftel Aug 08 '23 at 14:31
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    @quarague one tangentially related thing is that pure alcohol is a worse disinfectant than a 50%-70% solution (the remaining being water). Not sure it’s relevant in this case, but it could be (if the alcohol + water is breaking down the cell walls to help extract the compounds, for example). Either way, it’s a case that stuck out to me as going against intuition that “more active ingredient, more effective” – fyrepenguin Aug 08 '23 at 16:28
  • @fyrepenguin : I think that’s because it evaporates too quickly before it’s had a chance to kill germs. But I guess evaporative loss might be an issue if you don’t seal the bottle well, especially if it takes vanilla flavor with it – Joe Aug 08 '23 at 16:57
  • @fyrepenguin IIRC, you are close with the cell walls. It was something about the alcohol will not pass through the cell wall if it is too pure. – JimmyJames Aug 08 '23 at 19:49
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    @Joe, no, it's not evaporation. The same holds for isopropyl alcohol, and that doesn't evaporate really fast (neither does ethanol, but I've never handled pure ethanol) – Chris H Aug 08 '23 at 20:59
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    @quarague when you say "alcohol", I was assuming you meant pure ethanol. But everyday NaCl is a counterexample being [3 orders of magnitude less soluble in ethanol than in water](https://pubs.acs.org/doi/10.1021/je049922y). [Sucrose (table sugar) is also weakly soluble in ethanol compared to water](http://www.sciencemadness.org/smwiki/index.php/Sucrose). So are you referring to alcoholic drinks when you say "alcohol"? – Chris H Aug 08 '23 at 21:08
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    @quarague The solubility of most things is dependent on the degree of polarity of the solvent. Water is strongly polar compared to most alcohols, so things that are hydrophilic (such as most metal halides) tend to dissolve better in water than alcohols, and this effect can be strong enough to make things functionally insoluble in alcohols. Ethanol is considered a universal solvent because it _can_ dissolve most things, not because it’s particularly _good_ at dissolving most things. – Austin Hemmelgarn Aug 08 '23 at 22:31
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    No need to spring for some *151* if some garbage vodka in a plastic bottle will suffice. – Mazura Aug 09 '23 at 00:37
  • @AustinHemmelgarn That is a good explanation, thanks. I remembered the universal solvent/ can dissolve everything part but that is not the entire story. – quarague Aug 09 '23 at 06:54
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    In summary, it seems that the sole reason for not finding quasi-pure (95%+) food grade alcohol in recipes is really just related to expense or lack of availability in most places, but that its use is fine if not better than vodka, albeit diluted. After all, it is meant exactly for making homemade spirits and liquors. Following the discussion, I found indeed that for fruity/herbal liquors a dilution with water to achieve 40-60% alcohol content is recommended to capture the widest range of both water soluble and alcohol soluble constituents. – JJM Driessen Aug 11 '23 at 11:34
  • @Mazura here, "151" is far more commonly Lidl's (budget supermarket) own brand cleaning product range, which made your comment mean something completely different! – Chris H Aug 11 '23 at 14:26
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we do not want vanilla to evaporate too fast or too much or cause fire in the oven when baking.

veronica
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    Are you suggesting that pure-alcohol vanilla extract would do this, even once diluted by mixing into a recipe? If so, why does normal store-bought extract (which may have such a high alcohol content) not do this? – Sneftel Aug 09 '23 at 05:21