Harvesting yeast from the top

I have looked through the thread on yeast washing, all sorts of good stuff in there, but I notice that, for the most part, people seem to be harvesting yeast from the bottom of the fermenter. According to Michael Jackson's Beer companion (not really a scientific source, but it made me think) ale yeast ferments mostly at the top and was traditionally harvested by scooping out the foam from an active fermentation. Does this mean that if we harvest from the bottom we are selecting for a more lager like yeast? Also has anyone experimented with harvesting yeast from the krausen rather than from the yeastcake on the bottom?

Babylon said:

I have looked through the thread on yeast washing, all sorts of good stuff in there, but I notice that, for the most part, people seem to be harvesting yeast from the bottom of the fermenter. According to Michael Jackson's Beer companion (not really a scientific source, but it made me think) ale yeast ferments mostly at the top and was traditionally harvested by scooping out the foam from an active fermentation. Does this mean that if we harvest from the bottom we are selecting for a more lager like yeast? Also has anyone experimented with harvesting yeast from the krausen rather than from the yeastcake on the bottom?

Click to expand...

That is called [ame="http://www.google.com/search?q=top+cropping+yeast&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a"]top cropping[/ame].

Harvesting yeast from the cake will not produce lager characteristics. Those yeasts at the bottom are simply dormant yeasts that were at the top. Some yeast strains are good for top cropping, particularly English strains, because they produce a real creamy dense krausen that persists. Many American strains, though many have top cropped WLP001, do not produce a dense enough krausen to successfully top crop. In most cases the description from the yeast manufacturer will state whether the yeast is a true top cropper or not.

I like to stick to top cropping strains when I can. Its so much easier to get good viable yeast and there is no washing necessary.