Underpitching advice

[fakr]

Guys, this question is directed towards underpitching into moderately high OG wort (1.060-1.070).

I understand the higher the OG, the more yeast cells need to be pitched to do the job. My question is, if lets say you made a 5GAL batch of wort within the above mentioned OG range, and pitched 1 pack of lets say s-05, when fermentation slows or stops, could you not stir up the yeast cake at the bottom of the fermentation bucket and have it finish up the process?  Perhaps the yeast cake at the bottom isn't much good anymore due to the higher OG?

Does anyone here ever stir up the yeast cake during fermentation?  would this produce off flavors or anything worth noting?

[Kyle]

go for it: its called "rousing" the yeast.

This is easiest to do if pitching in a keg, you disconnect any hoses, and give the thing a good shake once a day for the first few days of fermentation if you are worried you under pitched.

It does not create any off flavours that I have noticed. It means the beer will need to settle a bit after the last shake to flocculate: that depends on the yeast, but with S-04, 36hours is sufficient.

[fakr]

Thanks Kyle.  Would this also apply to fermenting in a bucket?  Do you or have you roused the yeast cake in a bucket?

I'm assuming if you underpitch, and rouse the yeast to continue fermentation, that the fermentation period would be extended?

[Kyle]

underpitching is never desirable, but if its unavoidable, yeah, give the bucket a very gentle swirl / shake. I usually only do this with high gravity beers or mead, but I'm sure it would work either way. Just be careful to hold the airlock in place and be be prepared for a rush of CO2. A blow off tube is a good idea.

[fakr]

great, thanks.

[Shawn]

Especially since you're talking about dry yeast here, which is of course cheaper than liquid yeast, I'd just play it safe and pitch 2 packs.

Maybe you're more asking out of curiosity, but with the number of bad effects underpitching can have on beer (and obviously your financial input for a high-ABV beer is higher), it's better to follow pitching guidelines.

[Richard]

Under- or Over- is bad, as has been thrown about here a few times. It's no end-of-the-world in any event, and under is definitely much worse, but this thing is real handy:

http://www.mrmalty.com/calc/calc.html

[fakr]

Thanks Shawn.  It was more a matter of curiosity.  If I was short by a small amount (lets say short 20-30% total pitch), should I cancel the brew day, or could I get away with it as long as I roused the yeast cake and let it ferment for longer).  
I've been in that situation before, and ended up cancelling brew day.  doesn't happen often as I usually brew either 5 or 10 gal batches...this one was in between.

[Shawn]

Hmmm, tough call. For me, it would kind of depend on what type of beer you're brewing, exactly. Are you doing a large batch (over 5 gallons)? Is simply cutting back on the volume an option?

Rousing the yeast may help the beer get to its FG... it's more the risk of off-flavors and whatnot that I'd be worried about. I know that lots of people underpitch and claim their beer comes out fine (especially in the case of not making a starter when using liquid yeast), so it's a matter of personal/taste preference.

[fakr]

Thanks Richard, yeah, I have that calc in my favorites.