From strength comes forth sweetness

Is alcohol sweet? Does a high alcohol level in a wine make it taste sweeter? That’s the conventional wisdom, and it’s been mine too. But it’s always good to have one’s prejudices and ingrained assumptions questioned. If a shiraz with 15.5% alcohol tastes sweet because of the alcohol (ie the residual sugar is negligible), then why doesn’t a fino sherry at the same alcohol level taste sweet?

That was the simple question posed by someone on Jancis Robinson’s website forum recently, and I thought the answers were interesting and that they were worth sharing with a few geeks out there. (Actually someone did point out that “Very little regarding wine is ‘simple'”.)

One of the most useful answers quoted from the great Emile Peynaud’s  book The taste of Wine. He says that as well as sugars, there are other sweet substances in wine “which have one or more alcoholic functions, formed during the course of alcoholic fermentation” – ethyl alcohol, glycerol, butylene glycol, inositol, sorbitol.

Peynaud tested various alcohol strengths in water, and found that it “has a vaguely sweet, lightly sugary taste, clearly apparent by comparison with water but without the particular taste of alcohol being recognizable as such. The taste is different from the sweet taste of sugar while belonging to the same family of tastes. At 10% of alcohol there is a strong sweet taste along with a warm slightly burning sensation. This solution clearly shows the complex taste of alcohol. affecting both taste buds and the mucous membranes at the same time.”

Then he talks, of course, about the other aspects of a wine’s balance that affect the sensation of sweetness – acid, bitterness and saltiness.

The contributor to the forum who quoted Peynaud (at much greater length than this) also pointed out the contribution of fruitiness, and concluded that “I guess that in the end, it is just not about alcohol alone or sugar alone but a very complex interplay of many elements.”

Another contributor suggested looking at the role of volatile esters here: ‘Volatile esters are one of the major flavour components of fruit and can be perceived as “sweet” despite not actually being sugars. Look up esters in wikipedia, or google “sweetness and volatile esters” and you’ll see what I mean. And as alcohol is one base components of an ester, it makes sense that a wine higher in alcohol might generate more esters. I saw this in a previous life in the whisky business – whisky can appear “sweet”, or even “fruity” in varying degrees – despite having neither sugar nor fruit in it.’

But perhaps the question remains, why a wine at 15% alcohol seems sweeter than a sherry at 15%.

Again, it’s useful to talk about balance (one can never get away from the concept of balance in wine!): Another comment was:

‘To my simple mind is exactly the presence or absence of fruit (not alone, but in combination with acidity and tannin levels), that make the perception of sweetness of two wines with the same alcohol differ: I’m not a sherry expert or afficionado, but I believe that a Fino’s hallmarks would be a certain nuttiness, saltiness and maybe even earthyness in the nicest possible way – none of which we associate with sweetness. The blackcurrant, blackberry aromas of an Aussie Shiraz with the same amount of alcohol and res. sugar as the Fino would make it come across a lot sweeter, as we associate these aromas with fruit and sugar. It’s the way we have been ‘programmed’ and try as much as we like to be totally objective in tasting, we can not totally block these experiences.’

A number of people had mentioned glycerol as a factor in the difference between the sweetnesses of wine and sherry, and this was supported by David Bird MW, chemist and author of Understanding wine technology:

‘I think that the apparent sweetness is due to glycerol. It is a widely known fact that glycerol is formed during the fermentation of sugar. So, the more sugar in the original must, the more alcohol and the more glycerol. As glycerol has a sweet, smooth taste, so wines with high alcohol tend to taste smooth and sweet. If the alcohol is added, as with sherry or any other fortified wine, this extra glycerol is not present, hence the natural wines taste sweeter.’

So. We can happily continue finding alcoholic wines a bit sweet (and finding that another cause for objection to them, if we wish), and know that there’s good reason for it. It’s always comforting to have science supporting our beliefs.

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