highgravitybacon

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So the research differs greatly from practice. The research on flocculation finds that flocculation is increased by agitation, not reduced by it. Which makes sense, because if the yeast flocculation is a consequence of chemical bonds between two yeast cells, anything that increases the chances of yeast bumping into other yeast would then increase the flocculation. Then as clumps get bigger, they fall faster.

This differs from the usual practice of swirling the carboy to rouse the yeast. It would seems that trying to rouse yeast may be counter productive. However, the yeast can deflocculate in the presence of sugars so the swirling would then expose the cells to sugar to encourage further fermentation.

One text I read last night said that gentle swirling of 70-120 rpm maybe even using CO2 to bubble it would hasten flocculation.

It's not a causal thing, but I did notice a dramatic change in some carboys I shuttled around the house. For weeks, I'd been waiting for a beer to clear. It was a poorly flocculant yeast. For the longest time, I always treated these clearing carboys like fine china. Super gentle, don't want to disturb the yeast, etc.. But I wasn't very kind with these last two batches. Treated them like a rented mule.

Within days, they were rapidly clearing. It was after the fact that I did this bit of reading about flocculation so pick your logical fallacy and insert [here]. But I like the theory.

Has anyone else noticed this or played around with the idea that gentle agitation works to increase flocculation and thus clearing?

Here's a snippet from the undisputed source of all facts, Wikipedia:
For flocculation to occur the yeast must be flocculent and the environmental conditions (such as agitation, absence of sugars, a microamount of Ca2+, ethanol, etc.; Jin and Speers 1999). Several factors are important in cell-to-cell binding such as surface charge, hydrophobic effects and zymolectin interactions (see following). The importance of these forces in brewing yeast flocculation was unrecognized but work by Speers et al. (2006)[1] have indicated the importance of zymolectin and hydrophobic interactions. As the cells are too large to be moved by Brownian motion, for binding of two or more cells to occur the cells must subjected to low level of agitation.

beerbeerbeer123

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I wish i had a solid answer..but i think you run a higher risk of oxidation..I like to crash cool the beer.. its tryed and true..the agitation think i would be cautious

beerbeerbeer123

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Oh and im not saying it would not work.. just saying i would never try it to find out

eastoak

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i don't see this as a problem at all, how fast the yeast floc. once the beer is in the fermentor and the yeast are pitched i don't worry about it for a couple of weeks or more. it is interesting, the idea that yeast floc faster when agitated but it doesn't relate that well to homebrewing in my view.

AerationStation

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From Brewing Science and Practice; Briggs et al. 2004 pg 378

"The precise mechanism by which flocculation occurs is controversial and there is no
consensus that there is a single mechanism that applies to all yeast strains. The onset of
flocculation is observed in laboratory cultures that have just entered the stationary phase
of growth. Similarly, in brewing, flocculation occurs towards the end of primary
fermentation. Nevertheless, exponentially growing yeast cells can be made to flocculate
providing they are removed from the growth medium and washed and suspended in
water, supplemented with Ca2+ ions. Cells must come into contact with each other for
flocculation to occur, hence the surprising observation that flocculation and the vigour of
mechanical agitation are positively correlated. Thus, in well-stirred systems there is a
high probability that cells will contact each other and once formed, flocs are relatively
stable structures."

So I mean, assuming your Ca2+ con'c is good and your not adding any extra sugar later on in fermentation, swirling the carboy to get flocculation to occur is reasonable. Whether or not it's worth it is another question.

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highgravitybacon

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I have noticed in a completed starter, for instance, you can shake the ever living **** out of the starter, and it will floc out within maybe half an hour. Once they decide to throw in the towel, it's game over for the yeast.

dzlater

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I think it helps. When I move my Better Bottles, or give them a gentle shake, or a couple of thumps on the side, I can see yeast falling out of suspension. I don't go crazy with it, usually just moving it from the closet where I ferment it to the garage to cold crash is enough. Of course just giving it more time would probably have the same effect.

patthebrewer

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Personally I think this is only a topic for discusion with smaller batches with larger batches, the health of the prospective "agitater" could be endangered (I.e. Cardiac problems, muscular, skeletal problems, trauma etc.)

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highgravitybacon

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I'm going on record as think that a gentle swirling helps. I have a tripel that's been just kind of lazily sitting in secondary. About twice a day, I give it a gentle twirl to agitate the cloudy and clear layer. The rate of clearing has dramatically increased. Normally, in my 52F basement, this is a month long process of just sitting. It's been 3 days and half the beer is almost clear.

I know, it's incredibly scientific. I had some guys from CERN and the Goddard Space center come out to set up the test apparatus.

william_shakes_beer

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I find the posts above quite interesting, but the discussion only deals with half the system; from active fermentation to conclusion and flocculation. Once the yeast flocculates, swirling to "rouse the yeast" moves them back into the beer. Does this " unflocculate" them, decoupling them from one aonther and returning them to activity, or just move flocculated (and presumably dormant) yeast cells back into suspension?