Very old COS

[t0m]

I have an ancient tin of Coopers Original Stout, I think it's a couple of years old now. I was thinking a kilo of DME and a new pack of Safale-04, does that sound about right? Maybe slightly less DME because I am aiming for a 19 litre brew length. This is a test batch that I am going to try fermenting under pressure in a sixtel.

 

[winelight]

Personally I'd still use the full kilo of DME even for 19l... I think many people hereabouts brew this kit short to 21l anyway.

 

[bobsbeer]

What's the advantage of fermenting under pressure? Surely it makes it more complicated to transfer later as you will need to keep it under pressure.

 

[robsan77]

I heard that the yeast doesn't like being carbonated. Co2 is a waste product so its a bit like a fish swimming in a bowl of ammonia.
As a result you may not get good attenuation.

 

[jonewer]

Laws of physics would indicate that fermenting under CO2 pressure is not a good thing.

If your equation is Sugar -> Alcohol + CO2 then putting the squeeze on CO2 is going to shift the balance of the equation to the left.

Edit - that said, maybe theres some metabolic changes the pressure gives the yeast? Anyone?

 

[t0m]

I'll ferment under pressure then push it out through the beer line into a second sixtel. I serve out of sixtels so I have more than one coupler.

Possible advantages of fermenting under pressure might be:
* no contact with air at any point during fermentation
* natural carbonation
* don't need much headspace in the sixtel.

Worth punting a 2 year old kit on I reckon. :

I'll give it the full kilo or in fact 2 lbs as they say here in the **** end of nowhere.

 

[rpt]

Possible advantages of fermenting under pressure might be:
* no contact with air at any point during fermentation

But the yeast need oxygen in the early stages of fermentation to reproduce. So without air, don't you need a massive yeast starter?

 

[t0m]

Good point, it would need very thorough aeration. There are some flavour changes associated with extra pressure. The pH goes down from the dissolved CO2, and you get more diacetyl but less fusel oil. Can't be all bad because this is how most commercial beer is brewed.

You need to remove the check valve in the gas line and put in a gauge and pressure relief valve to avoid excessive pressure. There is a shed load of information here, from an evangelist of the process. http://www.homebrewtalk.com/wiki/index. ... rmentation