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-   -   Dry Hopping (or other post fermentation additions) - Why No Stirring? (http://www.homebrewtalk.com/f13/dry-hopping-other-post-fermentation-additions-why-no-stirring-372801/)

Joeywhat 12-08-2012 04:39 PM

Dry Hopping (or other post fermentation additions) - Why No Stirring?
 
I'm curious, why is stirring the beer not required when dry hopping, or adding other ingredients like vanilla beans or other solids?

When I added my vanilla into my keg, I dunked it a few times with a sanitized racking cane, but have otherwise left it alone. Obviously, after a few days I have some wonderful vanilla flavors and aromas in it. How does it distribute itself so well? The beans (in a hop bag) float on top, the dip tube is on the bottom.

I understand that it's not needed, I'm not arguing that, I'm just curious to know the science behind how it distributes throughout the whole beer while just floating on top.

mtnagel 12-09-2012 01:05 AM

For hops, the hops absorb the wort and the flavors come out into solution and then try to come to equilibrium with the entire volume of liquid in the container. Similar for the vanilla, the flavors are extracted out and disperse throughout the wort.

To simulate it, take a glass of water and drop food coloring it in and you can see how the color flows around and eventually equilibrium will be reached where all the water will be colored. Creamer in coffee would work too.

Revvy 12-09-2012 01:15 AM

Because once fermentation has ceased, you want to keep any agitation of your beer to a MINIMUM if any, otherwise you run the risk of oxidation. And your beer becomes liquid cardboard.

Flavors seem to mingle themselves ok without our help anyway. Things become waterlogged and that releases the flavors, or they slowly fall through the beer, or they release oils, or they're liquids themselves and they mix on their own, or are dilluted- all those things allow their flavors to affect the beer without our help.

Beer's pretty cool that way...it really doesn't need excess fiddling on our behalf. It tends to do what it needs to do on it's own....

nukebrewer 12-09-2012 03:49 AM

The scientific principle is referred to as diffusion. It's the tendency of a substance in solution to attain an equilibrium concentration throughout the solution.


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