What is the highest Specific Gravity that yeast can work in?

[kc_in_wv]

I am just curious

 

[Pappers_]

I don't think the specific gravity is what does the yeast in, its the alcohol. Different yeasts have different alcohol tolerances. Most of the producers list the alcohol tolerance on their websites. Generally, ale yeast will quit working at a lower abv than wine or champagne yeast.

 

[GinKings]

I think higher gravity musts do stress the yeast. When trying to brew really high ABV, it's common to feed the fermentation with additional sugars. I believe that's to avoid having a really high OG.

I don't know what the upper limit is. I get nervous when I get near 1.150. There is a mead from Poland called Jadwiga (sp?) that has a 3:1 honey to water ratio. If my math is correct, that's about 40 lbs in a five gallon batch! It's about 18% ABV. We tested a bottle and the FG was over 1.120! That puts the OG up around 1.260.

 

[OneCerebralSamurai]

Well from basic microbiology, microorganisms need a certain range of sugar/nutrient concentration in order for their metabolism to function. At very high gravities, the osmotic pressure will pull all the water out of a yeast cell and prevent it from metabolizing. This is why it's increasingly important to properly rehydrate yeast when pitching into high gravity musts. This is also the main reason that honey has such “anti-microbial” properties. It's simply so high in gravity than any critter that get's into it is immediately dehydrated and made inactive. (There are probably other anti-microbial properties to honey, but a straight sugar solution with the same gravity of honey will show much the same phenomena.)

The SG of honey is supposedly in the 1.400 – 1.450 range, and we know this is far beyond the max gravity for most yeast to do anything. I think the “maximum” SG would be very highly dependent on the yeast strain and how gently it was acclimated to the high gravity. If you use a very robust yeast (say, EC-1118), and properly rehydrate it and slowly increase the gravity of your must, then I think you should be able to handle something in the 1.200 – 1.250 range (maybe a touch more). Unfortunately, the resulting drink could be so syrupy-sweet as to be undrinkable (think vodka + pancake syrup). (I'd expect an ale yeast to have trouble around 1.150+)

Just my opinions...

 

[bknifefight]

There is a mead from Poland called Jadwiga (sp?) that has a 3:1 honey to water ratio. If my math is correct, that's about 40 lbs in a five gallon batch! It's about 18% ABV. We tested a bottle and the FG was over 1.120! That puts the OG up around 1.260.

Check your math, 40 lbs of honey in 5 gallons is 8:1, not 3:1 (which would be 15 lbs of honey, and seems to be common).

 

[OneCerebralSamurai]

Check your math, 40 lbs of honey in 5 gallons is 8:1, not 3:1 (which would be 15 lbs of honey, and seems to be common).

I think the numbers are for weight.

40lbs of honey ~ approx 3.3 gal. Therefore remaining 1.7 gal is water.

1.7gal water X 8lbs/gal = 13.6 lbs

40lbs honey/13.6lbs water = 2.94 ratio (close enough to 3)

 

[punkin]

Osmotic stress is surely a factor, hence the use of stepped fermentation.

Make a 10% potential and keep adding sugars as it uses them until the alcohol content stress the yeast to exhaustion. Bear in mind that stressed yeast will not make for a clean fermentation.


Seems to be a lot of questions here about getting the highest abv possible in a bottle. What is the purpose of high abv ciders?

Getting drunk quicker, or is it that you prefer the flavours of ethanol highlighted?

 

[kc_in_wv]

.

 

[Rockape66]

Water is 8.32 lbs/gal. 5 gal = 41.6 lbs. 40 lbs of honey to 5 gal water is damn close to 1:1 by weight. All information I have been able to find on meads recommend no more than 4.5 lbs of honey per gal of must.

 

[GinKings]

Water is 8.32 lbs/gal. 5 gal = 41.6 lbs. 40 lbs of honey to 5 gal water is damn close to 1:1 by weight. All information I have been able to find on meads recommend no more than 4.5 lbs of honey per gal of must.

My statement was 40 lbs of honey in a 5 gallon batch. Not 40 lbs of honey AND 5 gallons of water.

Water weighs about 8 lbs per gallon. Honey is denser and weighs about 12 lbs per gallon. 40 lbs of honey has a volume of approx. 3.33 gallons. If it's a 5 gallon batch, that means that only 1.67 gallons of water is needed (3.33 + 1.67 = 5). 1.67 gallons of water weighs 13.33 lbs.

A mead with 40 lbs honey and 13.33 lbs water is a 3:1 ratio by weight. I think you could also define it as a 2:1 ratio by volume (3.33 gallons honey to 1.67 gallons water).

Jadwiga is a Poltoraki style of mead. Here's a definition I found.

•poltoraki (półtoraki) - meads produced from the mixture of one unit of volume of honey and half of a unit of volume of water

I hope this makes sense.