Top Cropping Process

What are the advantages of doing this compared to collecting yeast from the bottom of your fermenter after packaging?

 

My attempt at "top cropping" did not end well. I didn't skim like you, but collected from a blow off tube and the resulting yeast did not start. I would be suspect of sanitation/oxidation problems using your technique. Have you had problems there? I would also be suspect of harvesting only the healthiest cells, potentially you are changing the character of the strain.

Your estimate of 1.2B/ml seems low if you're talking about yeast solids. If talking about yeast slurry (liquid/solids combined) it seems high.

I've had the best luck with making an oversized starter and pouring off the excess for the next brew day. Sanitation is easiest, you capture the full range of the strain, and the math works well. I typically get 3 cycles and can push it to 4 or 5. The controlling factor most often is something wild gets introduced and attenuation skyrockets.

 

Healthiest shouldn't be a problem, but I do wonder about the selective pressure you are putting on the yeast. You might end up with yeast that is less flocculent and more vigorously top-fermenting than the starting yeast. That might not be a bad thing though.

 

This is still done at all sorts of professional breweries all over the world. It’s a great technique provided you have the right yeast.

I believe there are top cropping breweries that have been using the same yeast forever, never starting new with a fresh pitch.

 

That is true. A local brewery has gone 100s of generations with top cropping British strains.

 

Magic Hat brewery was one that, as of a few years ago, were still using their original ringwood yeast strain...they had never purchased a new one at that time. Top-cropped all their batches for re-use and they had been a production brewery for over 20 years at that point....

I've stopped top cropping (as I've gotten lazier) and use the same technique that @PortLargo described. @hoptualBrew i'm interested to hear how it goes for you. I would often end up making a starter anyway just to assure myself of yeast health. Not sure if you can view this...but this was a good read from Colin Kaminski in the yeast health department: https://byo.com/article/the-new-starter-a-novel-method-for-ensuring-yeast-vitality/

 

Good or bad, if you bypass the "quick flocc'ers" you have changed the strain.

Absolutely. When I toured Ommegang they were shoveling the top-crop yeast into barrels. Only time I've seen a stainless steel shovel.

Link requires a membership to view. Any chance you could "copy and paste" the article without running afoul of the copyright police?

 

Not directly answering the question but,

I'm not convinced that collecting krausen for subsequent batches has all that much effect on yeast flocculation characteristics. Reusing yeast that has settled to the bottom of the fermenter certainly self selects yeast that fall fast, or at least leaves behind the yeast that are still floating around. This much is not debated.

But when yeast is collected during high krausen all of the yeast is active. There is little settling. Just very active yeast. Any yeast that have dropped are pretty lazy and I don't want them on my job anyway.

I've skimmed yeast many times, and the subsequent batches go off as well as dry strains or better. Burton Union systems went on for generations with little apparent mutation. My experience is really limited but I don't equate bottom harvesting and top harvesting as the same or even similar.

Am I way off?

Edit.
A production brewery would be unlikely to top crop and store the yeast for very long, if at all. So refrigeration is going to be a variable on the homebrew scale. A starter might be a good idea. But if you need to make a starter I don't see much point in top cropping.

 

FWIW your reasoning appears sound to me. At the beginning of an ale fermentation all (or at least the vast majority) of yeast will be happily fermenting on the top portion of the beer. If you were to skim yeast cells then it makes sense to me that you have a broad spectrum of yeast cells - I personally do not see a 'selection process' going on here.

Cheers!

 

Nice vids. I have a account but never post on IG. Have you done any brewing vids. I'm about to finish my first and the second will be done in a few weeks that i'll post on YT.

 

Is it at all possible to top crop from a fermenting lager? I have heard that it should not be done, but since there is often a good crop of krauzen there on top, why shouldn't it be done?

 

In a lager fermentation, the proportion of yeast in the krausen (which also contains proteins, hops matter, etc.) is lower. I guess you could try it, but I doubt the yield would make it worthwhile. And if there were enough yeast in the krausen to make it worthwhile, I think I'd bump the pitch rate up even higher than normal for a lager fermentation, to make up for the yeast that would be lost to cropping.

 

Is there THAT much protein floating on top (I generally have extremely little hop matter going in my fermenter - besides it would be of a darker color)? Is it worthwhile removing that protein?

 

Some traditional German Brewers skim the Braunhefe, the dark stuff, to result in a more refined taste.