Recently a reader asked me to determine the alcohol content of a barley wine of his (and a very fine one it was too) which his calculations showed should have an ABV of about 23.8% using the Balling formula. The OG was about 43P and TE came in at 9.58P (lower than his estimate), which actually implies almost 26% again using the Balling formula. Remember that the Balling formula is based on conservation of mass so the question becomes "Where did all that sugar go?" (about 9P worth is unaccounted for). Sugar either 1) stays in solution to contribute to True Extract 2) gets converted into carbon dioxide 3) gets converted into yeast biomass or 4) gets converted to alcohol.

While puzzling over this (and re-running the assay) I remembered that when I'd spilled 18% ABV cyser on my hands the cooling effects of evaporating alcohol were very evident. So I made up a solution of a little pure alcohol in water and checked the concentration. It was 22.72%. I let the beaker sit for 20 minutes and then checked the strength again. It was down to 21%. Thesis confirmed - alcohol leaves concentrated water solutions very quickly. The brewer confirms that this beer spent weeks in carboys, was racked etc. So I think his sugar got turned into alcohol and carried off by the CO2 evolved and air currents during handling. This leads to a couple of questions:

1) Has anyone else here had experiences which tend to confirm or deny my suspicion?

2) Is there some sort of practical limitation caused by alcohol evaporation as to how strong a beer (or wine) can be fermented given that the yeast are not the limiting factor?

3) Are there any techniques (such as cold fermentation) which are successful in preventing loss of alcohol from strong beers and wines?

4) Has anyone here brewed a beer with alcohol concentration above 20% v/v without resorting to freezing, fortification etc.?

-AJ DeLange

RESPONSE:

Measurements of S.G., balling, density, gravity, Plato etc. in the presence of alcohol, especially higher levels of alcohol (15 - 20+%) is very deceiving. The presence of the alcohol with its minus gravity gives a false low Plato indicating a larger amount of sugar has been converted to alcohol than actually has been converted. This is a partial answer. There may be other factors.< p< it.

The alcohol does not usually evaporate as fast as you indicated. I work routinely with wineries that ferment up to 20+% alcohol with no evaporation problems during fermentation, processing, storage and aging.

Now, getting the fermentation up to 20+% alcohol can be a problem. It can be done with in 12 days with the right strain and volume of yeast, proper nutrient addition, aeration and special protocol for sugar addition. Fermentation temperature maintained between 70 - 89F. There are many regular strains of yeast that will ferment up to 20+% alcohol. The secret is TLC (tender loving care).

The Guinness Book of Records is supposed to be 23% and is held by brewer in the UK. If you are interested in trying for a 20+% brew, I will be glad to work with you.

Dr. Clayton Cone