Overpitching

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clive-s
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Overpitching

Post by clive-s » Sun Mar 07, 2021 5:51 pm

Greetings,
I have only done a couple of beer kits.

If I understand it correctly Overpitching is when you have volcanic followed by a short hard fermentation, rather than a slow longer fermentation..

I mainly brew Belgium style and Stouts. My first fermentation is approx three weeks, then move it to a pressure barrel for as long as possible.

To avoid a volcanic fermentation, and have a slower and longer fermentation. Could I split the starter yeast into three beakers, keeping two in the fridge and adding them to the wort weekly?

Regards,
Clive

f00b4r
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Overpitching

Post by f00b4r » Sun Mar 07, 2021 6:01 pm

Overpitching is just pitching too many yeast cells. Over pitching is very hard to do at a homebrew level unless you are pitching onto previous yeast cakes or brewing German wheat beers (they like a lower pitching rate to get the best flavours from the yeast). Experienced all grain brewers who have very tight processes can have the vast majority of fermentation done in the first 48 hours so it isn’t really something that they try and stretch out and you don’t usually want to underpitch.
Stouts tend to be pretty volcanic fermentations due to the dark malts in there (the question of why that is someone else would have to answer).
What do you ferment in?

guypettigrew
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Re: Overpitching

Post by guypettigrew » Sun Mar 07, 2021 7:38 pm

As f00b4r suggests, over pitching and the speed/length of fermentation aren't directly connected.

Also, as f00b4r says, most fermentations are finished in a few days. One of the main reasons some homebrews taste horrid, in my opinion, is because they are left far too long in the fermenter. The yeast slows down and begins to drop out, air can get in and oxidation and infection become a real possibility.

Three weeks is far too long for the fermentation of a stout. One week absolute maximum, probably four to five days. Cool it in the fermenter, if you can, then drop it into a barrel, leave it at about 12°C for a week or so then try it.

Guy

McMullan

Re: Overpitching

Post by McMullan » Sun Mar 07, 2021 11:26 pm

Obviously, there is actually a relationship between yeast pitching rate and fermentation performance, but, generally, we don’t need to worry about ‘over’ pitching. Worry more about under pitching, especially as it seems to be something promoted by home-brew lore, dodgy calculators and ‘convenient fixes’ to avoid the simple task of making a yeast starter.

I’m not sure what a ‘volcanic’ fermentation looks like, but I’m guessing it involves foam escaping from the fermenter. Usually it’s associated with insufficient headspace. Over filling the FV, in other words. A ‘no-shit Sherlock’ moment really. A particular ‘problem’ with some British and Belgian yeast strains. The ‘top heavy’ ones. Even more so when fermenting a dark ale that had black malt or roasted barley in the grist. These roasted malts contain foam-promoting compounds. It sometimes causes issues during the boil too, if there isn’t sufficient headspace in the kettle.

Edit: The point I wanted to make, before falling asleep, was that it might look like you have a vigorous, even 'over' pitched, fermentation going on, but appearances alone can be quite deceptive. It's always best to fact-check with something like an hydrometer. Note too that a big dark beer like a stout is probably going to take more than a week to reach FG, even if you're successful at 'over' pitching by quite a lot.

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