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Top Fermenting Yeasts - Skim Or No Skim?

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Bribie G

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Have been using genuine Nottingham Yeast for three ale and stout brews and have been harvesting yeast cake and reviving it in starter bottle for next brew.

This time I got a real 'cauliflower head' as it's a top fermenting UK yeast. Also by coincidence the day before yesterday I watched Michael Jackson's TV Beer Hunter episode re British Real Ales. Visiting the Bateman's Brewery, Michael and the head brewer are inspecting an open fermenter of ale and the comment is made "It's been skimmed and is about ready for racking"

Then, something I had forgotten over the years, came back to me. While home brewing in the UK in my former life I followed two gurus, CJJ Dennis and Dave Line (both best selling textbooks still in print) and there was a big emphasis on skimming the krausen head off the top fermenting brew after the initial vigorous fermentation as it contains all sorts of crud that you don't want to fall back into the brew. If I remember correctly the major culprit was the very bitter hop oils that end up in the foam. Made sense at the time and I would always skim after two or three days in the fermenter. (And in those days in the UK I'm talking plastic garbage bin :eek: - great for top ferm, however)

Obviously not an issue in OZ with lagers or even - for example - Morgans or Coopers cans.

However with recipe and AG brews, do any members here skim their top fermenting ales when using a true ale yeast ? Tempted to do this with the current one.
 

buttersd70

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Sometimes I do....the whole skim the top because its bad if you dont issue was done to death on here several months ago, and I don't really have too much of an opinion on it. (makes a change :lol: ).
I have done it a few times with 1275, but to be honest, could detect no difference between skimmed and unskimmed in the final product.
 

Muggus

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Not sure if i'd recommend doing it until you're at the point where you're sure the yeast has done what you want it to (stopped fermenting?) and you're ready to rack/bottle.
I made the mistake of using the krausen of a hefeweizen that was fermenting away nicely and tasting amazing, and using a few scoopfuls to start up a weizenbock i'd just brewed. The weizenbock turned out great, the hefeweizen went to shit. In a beer of that style, where the yeast really dictates the ideal character, I don't think its advisable.
 

PostModern

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You don't skim the top to remove "Bad Stuff"(tm)! You skim to harvest the most active yeast and pitch it in your next brew!
 

Dr Gonzo

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I recall the need to skim being that the brown scum that forms on top of the krausen foam, when exposed to oxygen, can oxidise to form harsh compounds which, when allowed to fall back through to beer may produce off flavors. In a sealed fermenter this is not an issue, but in an open ferment it may be.
 

mfdes

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There is no yeast as vigorous and clean as that which you skim off the top of a brew. This is because the yeast has flocculated at the optimal stage in its metabolism to be at its peak of health and nutrient content. Thus yeast skimmed off the top of a top-fermented ale makes a far better re-usable than the yeast cake off the bottom. This was the traditional method of cropping yeast in many breweries and resulted in no loss of vigour, which yeast harvested from the bottom can do in the long run.
I do this in two ways: When open fermenting (which I no longer do) i would skim once at high krausen to remove trub and hop resins, then again a day or two later to crop almost pure yeast.
Nowadays I use a glass carboy and a blowoff tube. I blow off for a day or so and then start collecting yeast. I use a well sanitised tube and jar, covered with sanitised aluminium foil. Works a treat and the yeast seems to last a longer time in storage than bottom-cropped stuff. I still make a starter if the yeast is more than 3 weeks old when I plan to pitch it though,
 

Bribie G

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Thanks for the tip, I'll try that next time as I want to keep a vigorous colony of Nottingham yeast going - about to do one lager brew for Christmas but apart from that it will be all ale brews until after Easter so I'm looking to develop skills in yeast culturing.
 

PostModern

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Thanks for the tip, I'll try that next time as I want to keep a vigorous colony of Nottingham yeast going - about to do one lager brew for Christmas but apart from that it will be all ale brews until after Easter so I'm looking to develop skills in yeast culturing.
Try starting with something nicer than that. Ringwood or Whitbread or Burton or something interesting. Nottingham is a dry, bland, boring yeast.
 

mfdes

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For English bitters and Pale Ales I absolutely love the Wyeast 1968 yeast. It has the most fantastic flavour profile. It does especially well with lower gravity beers, such as bitter and mild, as it is a low attenuator.
MFS.
 
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