Why does cold crashing clear beer?

[mongoose33]

I have looked online to find out this question and haven't found anything.

I have a theory (CO2 attached to yeast create bubbles that help them float, and the CO2 is absorbed into the beer when it's cold crashed and thus the yeast sinks). But I have no idea if that's correct or if something else is operating.

Anyone know the answer to this?

 

[Sailingeric]

Yeast get cold, they snuggle together to stay warm, get to heavy to float and sink the bottom. That is my theory and I am sticking too it

 

[kombat]

It's harder for things to stay dissolved in cold liquid vs. warm liquid. You chill the beer, stuff precipitates out of solution and sinks to the bottom. Adding gelatin helps this, because the opposing ionic charge of the gelatin attaches the particles to stray precipitates in the beer, increasing their combined weight and pulling them to the bottom faster.

 

[poptarts]

Proteins and polyphenols (tannins) form agglomerations (basically bind with each other to form larger molecules) which become insoluble, at cooler temps as @kombat mentioned, and precipitate out of solution. Yeast also tend to go dormant and drop out as well if they are still in suspension.

 

[SanPancho]

its not the co2, that actually is more likely to dissolve and stay dissolved in the beer as the temp drops.

lower temps mean the yeast move and eat and multiply more slowly. some ale yeasts drop completely at 60, some lager yeasts take weeks to fully drop at 35F. but *on average* the lower you go the more yeast go dormant and fall to bottom.

and as noted above, all the other molecules slow down their movements as well, which means they are more likely to bump into each other and stick together until their weight pulls them down- like proteins, trub, hop particles, remaining yeast, etc.

its like if you had a table full of spinning tops, and you could magically slow down their rotation speed all at once- slow them down enough, and they fall out of motion.

 

[cegan09]

Think about trying to dissolve sugar (or a drink mix) into water. Cold water will only accept so much before it just rejects the rest which collects on the bottom. Hot water will dissolve a lot more of the same additive.


It's not perfectly the same with cold crashing, but it should give you an idea. Things are less soluble at colder temps, so they drop out.