to skim or not to skim

Hello all from a new member, first post.

American brewers often use narrow necked glass carboys for fermentation, so they can't skim off excessive yeast foam and brown sludge, wheras I skim 2 or 3 times a day. Which is best?

I think probably every person on here will say the same thing, that you should not skim the krausen. I have never skimmed and do not see the point in doing it. Any excessive yeast will just settle to the bottom after its done anyways.

+1 - What he said.

+1 on what they both said.

Welcome to HBT, Bob!

+1 x3


Welcome!

Even if there were some slight benefit to skimming you'd be risking contamination by opening the fermenter so often.

Traditional commercial breweries practice skimming for a variety of reasons.

Take Samuel Smith's, for instance. The yeast used in the stone square system is very flocculant and must be roused, but at the end of fermentation the yeast rise to the krausen level. From there they are skimmed for repitching, as opposed to racking the beer from the yeast cake and harvesting from the cake.

"English yeast strains are prized for their resilience and hardiness (resistance to mutation), and for their ability to remove themselves from the fermentation when their work is done (flocculation) perhaps more than the flavors they produce. After the bulk of the sugar is converted to alcohol, CO2 and flavor compounds, English ale yeast rise to the surface of the fermenter on bubbles of CO2. Once there, they can be scooped from the surface, or "skimmed". This yeast is the most viable (alive), and is prime yeast to be used for subsequent repitching. It should be relatively free of dead cells, trub and bacteria and so perhaps will need to be repropogated less often. I know of one brewery that has been using the same strain for over 200 years."


Unless you're continually repitching a particular yeast in search of a house strain, there is no reason to skim krauesen.

Cheers,

Bob

+1 on what's been said. I've read about skimming only in the context of wanting to collect yeast for re-use, but even then most people just collect from the trub after primary fermentation and that works great. While it's tougher to infect a batch than most new brewers think, there's really no reason to open up your fermenter more than you need to, it's just asking for trouble. If you give the beer enough time to condition, it'll clear itself up fine regardless.

Thanks to all for a very quick response, I was under the belief that the brown sludge could give unwanted flavour to the brew. I have been brewing for 40 years, and having just retired, with more time, am going to move to full mash. Thanks again.

And by the way - welcome to the forums

Danek, I am in Kettering Northants..

BOBTHEukBREWER said:

Danek, I am in Kettering Northants..

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Nice to see another brewer from this side of the pond . Hope you're managing to avoid the gales!

BOBTHEukBREWER said:

Danek, I am in Kettering Northants..

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Not sure if this would be of any interest to you, but I've just seen on eBay there's someone in Kettering selling 48 empty pint bottles. Maybe useful if you need to stock up on empties?

http://cgi.ebay.co.uk/beer-cider-br...57326820QQcmdZViewItem?hash=item180257326820&

What is your purpose for skimming? If it's for yeast ranching then yes. If it's to clear the beer then no way Jose. If it is to ranch, then 1 or 2 scoops is enough to make a starter for ranching.

By skimming off, you are also losing the benefit of the yeast cleaning up the beer as it flocculates downward (for ale yeast). As the krausen falls, it takes all sorts of stuff down with it (think hop floaties, and excess proteins).

The yeasts are really good at cleaning up their house after fermentation...

Revvy said:

By skimming off, you are also losing the benefit of the yeast cleaning up the beer as it flocculates downward (for ale yeast). As the krausen falls, it takes all sorts of stuff down with it (think hop floaties, and excess proteins).

The yeasts are really good at cleaning up their house after fermentation...

Click to expand...

There's so much yeast in suspension that there's going to be plenty left over to still clean up after themselves. I even asked Chris White about this at NHC and he said, contrary to my own thoughts, that it isn't as big deal as what some people play it out to be.

I have skimmed some Cal-Ale yeast to start making some super yeast. I'll keep skimming it for 3-4 more batches perhaps.