Starving Yeast

[huesmann]

I understand that instead of using sulfate/sorbate to halt fermentation, one can simply starve yeast. I assume this means you just rack to secondary or tertiary for some period of time. How long? How do you know when all the yeast is dead?

 

[Yooper]

I understand that instead of using sulfate/sorbate to halt fermentation, one can simply starve yeast. I assume this means you just rack to secondary or tertiary for some period of time. How long? How do you know when all the yeast is dead?

It won't be dead. It'll just be dormant. You can ferment the mead dry, and rack several times and when it's crystal clear and no longer dropping lees it can be bottled. If you want to sweeten, though, it still must be stabilized as fermentation will restart when you add more fermentables.

Stopping an active fermentation is like stopping a freight train. You can't easily halt fermentation with sorbate and sulfite. It's used to stabilize a finished mead, and then the mead is sweetened. Sorbate doesn't kill yeast, either, but it inhibits reproduction. That's why you start with a finished, clear mead.

If you want a high ABV sweet mead, that's pretty easy. You just keep feeding the mead more honey until the yeast have reached their alcohol tolerance and quit. That works well, except some yeast strains can go over 18% ABV, so the mead will be rocket fuel for a few years!

 

[huesmann]

But what constitutes a "finished mead?"

If you want to do that sweet hi-test mead, do you add honey after initial fermentaion, or do you just pack as much honey as you can into your starting must?

 

[Yooper]

But what constitutes a "finished mead?"

If you want to do that sweet hi-test mead, do you add honey after initial fermentaion, or do you just pack as much honey as you can into your starting must?

Since mead can be a tough ferment (very little nutrients in honey), incremental feedings work best.

 

[huesmann]

Does the alcohol actually kill the yeast, or does it just make it go dormant?

 

[MedsenFey]

At high enough levels alcohol will kill them.

 

[huesmann]

How long does it take to kill the yeast once the tolerance level has been reached?

 

[Yooper]

How long does it take to kill the yeast once the tolerance level has been reached?

It's not like you hit 20% ABV, and suddenly they all die. It's more of a gradual poisoning of them- they will start dying individually until there are no more left. This might start at 16% or so, and then even the most vigorous will usually be done by 20%.

 

[huesmann]

Right, but how do you know for sure? Say your yeast is supposed to be good up to 18% and your SG calcs tell you you've hit 17.5%. Do you wait a few more weeks? Suppose you wait a few more weeks and it's still 17.5%?

 

[Yooper]

Right, but how do you know for sure? Say your yeast is supposed to be good up to 18% and your SG calcs tell you you've hit 17.5%. Do you wait a few more weeks? Suppose you wait a few more weeks and it's still 17.5%?

You'll never really know- unless your mead stops at an SG above dry. That is, if you stop at .998, say. And it stays there. And stays there and stays there. Then, when you add more fermentables, it stays there. Then you know it's done.

 

[fatbloke]

Just to mention the point, that the alcohol is the waste product after the yeasties have munched the sugar.

So by making a batch that's strong enough to kill the yeast, what you've actually done is make them drown in their own sheeeeit!

The downside of that, is that the batch will probably taste "alcohol hot" and take a millenia to smooth out.

regards

fatbloke

p.s. ha! I'd never thought about it like this, that we're making meads so we can drink the yeasties pooh!

 

[MedsenFey]

Right, but how do you know for sure? Say your yeast is supposed to be good up to 18% and your SG calcs tell you you've hit 17.5%. Do you wait a few more weeks? Suppose you wait a few more weeks and it's still 17.5%?

Brother Adam, the renowned mead maker of Buckfast Abbey, documented that in his high gravity batches that stopped, it was common to see fermentation restart when the temperature warmed up during the summer for up to two years. If you have a batch that still has residual sugar, and which has stopped below the ABV tolerance of the yeast, I'd suggest stabilizing with sorbate/sulfite (or some other mechanism to insure you don't get bottle bombs), or I'd suggest really long aging before bottling.

Medsen