What causes the burning taste of hard alcohol?

[Kevin Liu]

When people describe a liquor as "harsh" or "smooth", they are typically referring to the presence of that characteristic "burning" taste of ethanol. What is the physiological or chemical explanation for this sensation? It should be clear that the taste isn't strictly bound to alcohol content, since many higher-proof spirits are consistently known to be smoother than lower-proof varieties.

I'd like to better understand the mechanism in order to better control the taste of cocktails, infusions, etc.

Here are some theories I've come across, any elaboration would be really helpful:

- ion channels in taste receptors are temperature dependent, so lower temperature = less burning

- alcohol is evaporating off the tongue

- the overstimulation of vanilloid receptors (VR1) in the mouth

- presence of impurities/bitter agents

And here are some ideas I'm playing with for mitigation of burn

- presence of dissolved sugar increases space between ethanol molecules, reducing perceived alcohol burn

- neural adaptation leads to less burning sensation over time

- salt or acid seem to neutralize the sensation (tequila shots?), is this a chemical reaction or a neural adaptation thing?

Thanks in advance!

[Panaderia Canadiense]

I can't really speak to the chemistry of it, but....

In the case of Cachacas and Aguardientes, sugar is normally used to lessen the burn, and in the case of Aguardiente, sugar and heat (Canelazo) leads to a drink that may be about 80-proof but has the flavour of fruit juice.

[slkinsey]

The answer is definitely complicated, but certainly starts with chemesthesis (also sometimes called by its old name, "common chemical sense"). It seems clear that ethanol is sensed this way, and likely that fusel alcohols are especially strongly sensed this way. Of course, these things will be sensed more strongly the higher the concentration, which explains why higher proof spirits produce a stronger chemesthetic sensation than lower proof spirits and also why "dirtier" spirits produce a stronger chemesthetic sensation than "cleaner" spirits. We also know that sensory perceptions are influenced by other sensory perceptions. For example, the perception of sweetness is reduced at lower temperatures, which is why warm cola tastes so much sweeter than cold cola (and also why frozen drinks need more sugar to taste balanced). I don't see any reason why the perception of chemesthetic sensations wouldn't also be influenced by other sensations. It's unclear to me the extent to which these interactions have been studied, however. Here (PDF) is an interesting paper to get started understanding it.

Edited September 2, 2011 by slkinsey (log)

[bostonapothecary]

We also know that sensory perceptions are influenced by other sensory perceptions. For example, the perception of sweetness is reduced at lower temperatures, which is why warm cola tastes so much sweeter than cold cola (and also why frozen drinks need more sugar to taste balanced). I don't see any reason why the perception of chemesthetic sensations wouldn't also be influenced by other sensations. It's unclear to me the extent to which these interactions have been studied, however. Here (PDF) is an interesting paper to get started understanding it.

perception of these things is so multi-variable (because its so multi-sensory) its mind boggling. reality is highly "constructed" by the mind and the degree to which it happens in food is quite staggering.

the way one sense changes the threshold of perception of another is tied to our reward systems. perception is also tied to our ability to pay attention which is structured for survival. our attentional spotlight defaults in a predictable order across the senses as we engage in multi-sensory perception.

the pineapple chunks in the stoli-doli jar may have an alcohol content of only 20%, but they taste like everclear because the haptic textural data added by the fruit changes the threshold of perception of the alcohol.

thermoception is also widely known to change the threshold of perception of alcohol. heating the liquor slightly makes it tastes "hotter" while chilling it to extreme levels creates an attentional distraction away from the alcoholic burn. our attentional spotlight therefore gravitates to extreme levels of thermoception over this particular type of chemesthesis.

sweetness might have a similar effect on alcohol as it does on bitterness. our reward systems reinforce behavior with their construction of reality. true, campari is bitter, but it is also redeemingly sweet from the perspective of the reward system. the mind reduces the perception of risky bitterness because it has also found calories and wants to reward and reinforce the behavior. alcohol could have a similar relationship and aromas that "converge" with gustatory sweetness could also yield a similar effect.

one of my theories is that another reward system that finds value in attentional distractions (distractions dispel anxiety?) eventually over takes the reward for sweetness and that is why many of us eventually prefer and even crave various forms of "dryness".

a book i'm reading now is "the handbook of multisensory processes". it has no articles that specifically cover this topic, but what you find is that many multisensory processes work similarly and you can test and apply ideas from one process that is well studied to another. related to specifically to culinary, the book has a phenomenal article titled "sweet and sour smells: learned synesthesia between the senses of taste and smell" by richard j. stevenson and robert a. boakes.

Edited September 2, 2011 by bostonapothecary (log)

[Kevin Liu]

Thanks for the thoughtful responses. I think both chemesthesis and thermoception are really important. I especially like the example of the low-alcohol fruit tasting strong.

I did a little more research into vanilloid receptors and found some interesting reading:

source

However, for many years it has been known that ethanol produces taste responses that include a burning sensation (Hellekant, 1965; Danilova and Hellekant, 2002; Sako and Yamamoto, 1999). The presence of the TRPV1 channel in taste receptor cells (Lyall et al., 2005a-c) provides a possible mechanism for the burning effect of ethanol. Indeed, previous studies in nociceptive neurons that innervate the face and mouth, as well as TRPV1-expressing HEK293 cells, showed that TRPV1 channels responded to ethanol at concentrations of 0.3-3% (about 65-650 mM) (Trevisani et al., 2002). Specifically, ethanol potentiated the response of TRPV1 to selective TRPV1 agonist - capsaicin and protons (acidic solution of pH 6) and lowered the threshold for heat activation of TRPV1 from 42 °C to 34 °C, which is near the temperature of the tongue. This provides a likely mechanistic explanation for the ethanol-induced sensory responses of inflamed tissues (Hirota et al., 2003)

So it looks like the jury may still be out on specifically how the burn we associate with alcohol actually works, but I'd be willing to bet its some combination of all these factors.

[Kevin Liu]

Hey - someone answered my quora question on the topic and did a stand-up job with it. I can't really summarize it because it's already a summary of lots of interesting research.

Full answer here: http://www.quora.com/Tastes-of-Alcohols/What-is-the-chemical-physiological-explanation-for-the-burning-taste-of-hard-alcohol