High alcohol and SO2 is an aroma killer explained via science

[Don Giovanni]

High Alcohol and SO2 is a Aroma killer explained via science : case for lower alcs and SO2 in wine

the big debate over high alcohol and some experimenting that I did this past harvest is now explained by science in the new book that I have been reading 'Taste Buds and Molecules' page 38 specifically.

first to the experiment I did and have been evaluating ...

the subject grape is a aromatic grape Cayuga White grape a hybrid who's life begins in 1947 and then brought to the wine world in 1972 by Cornell... it's a very good winter hardy grape that when fermented will give notes of peach, pear, wildflower, honeysuckle as the primary notes...

the experiment I fermented three batches in stainless and the following are the results

CW -1 ....CW-2.... CW-3

PH 3.22 ... PH 3.21 ... PH 3.33

T.A. 7.5 g/l ... T.A. 6.9 g/l ... T.A. 7.8 g/l

R.S. 0.9 ... R.S. .06 ... R.S. 2.4

Alc 13.1 ... Alc 13.1 ... Alc 13.9

Free SO2 52.8 ... Free SO2 60.8 ... Free SO2 49.6

each had Birx of 19 and each has sugar added to boost the alc... the yeast was a control commercial yeast not being disclosed

...

CW-1 the wine had the best aroma fully of life very pleasant very big...

CW-2 the wine had a nice aroma 1/2 the bigness as the CW -1 still nice but the SO2 was in the air and muscled out the aroma... in time as the SO2 binds or if decanted blows off the wine will open up , but it's my experience it won't be as perfect as the CW-1 wine

CW-3 is everything wrong with this high alc wine the aroma is gone and hiding far in the background ... hard to believe it's the same grape... muted is the kindest description ...

so molecular weight in wine as displayed by aroma comes to play...

the first CW-1 had the greatest balance where the alc allowed the lowest molecular weight of the aroma that has the most aroma to come up and out of the glass....

CW-2 had more SO2 that gave off the flint match head smell and competed with the lowest molecular weight in the aroma by muting the aroma... it was a bully in that glass...

CW-3 was a mess although the SO2 was the least and not far off the control wine CW-1 ... the high alc. killed the aroma by not letting the aroma out trapping the lowest molecular weight aroma in the wine

we know that "when wines with the normal alcoholic content, those between 10% and 14%, the aromas are released in successive stages. First come the compounds of low molecular density. then the later, depending on the interaction with oxygen in the air of the wine, then the higher density compounds. In higher alcohol wines the low density aromatic compounds are rapidly inhibited, leaving room for only the high density compounds." page 38 Taste Buds & Molecules by Francois Chartier.

So I did this experiment and found the results but lacked the science as to why... then by the gift of information...Bob recommended the above book and a light went off I had my answer in English as to the science... go figure...

if the winemaker does not let the wine come in at a much lower alc specific to that grapes expressive aromatic low molecular weight aroma then the it will kill the aroma, also if the winemaker is too liberal with SO2 then again they are killing the aromatic low molecular weight aroma... and last if they do both the above they lose the personality of the grape and produce a unnatural high density aroma only...

[Dexter]

Just to make sure I'm reading this right, you allowed the fermentations to go to different lengths for the higher alcohol wines, right? I'd be particularly interested in seeing what the results would be if you'd arrested the fermentations all at the same point, and changed the SO2 and EtOH levels artificially, just to eliminate the variable of fermentation byproducts (as well as more time for blowoff, etc).

Also, did you control for total sulfur, or just free?

[Don Giovanni]

Just to make sure I'm reading this right, you allowed the fermentations to go to different lengths for the higher alcohol wines, right? I'd be particularly interested in seeing what the results would be if you'd arrested the fermentations all at the same point, and changed the SO2 and EtOH levels artificially, just to eliminate the variable of fermentation byproducts (as well as more time for blowoff, etc).

Also, did you control for total sulfur, or just free?

yes I allowed fermentations go to different lengths for the higher alc...

The first and last were free SO2 the second was hit to arrest the SO2 at that level...the third I lowered the tank as the yeast were dying anyway due to alc toxicity to the yeast... I have done what you proposed using white lightning or pure alc... the higher alc killed the low density molecules of the aroma rendering the wine muted... playing with the SO2 's has been done again the result being muted low aromatic molecular density aroma... those experiments we do all the time as they are the easiest...

cheers !!!