How does cold crashing work?

[noob1979]

I have a beer in a fridge at between 35 and 40 F right now until tomorrow when I bottle. I'm doing this because threads on HBT tell me the clarity of the beer will increase as the beer is chilled to 35 F for a few days.

I was wondering if my conjecture on this phenomenon was correct, or if I need a primer in cold crashing?

I think the temperature of the water causes an increased density in the water, and this increased density does not allow the beer to hold large amounts of protein and trub. I also surmise the process works top to bottom, so the longer the fermentor is in the fridge the more compact the trub will become in the bottom of the fermentor.:cross:

If any of you have had the ability to observe the process, or simply have a better understanding on how this works, please let me know.

Thanks and Cheers

 

[djfriesen]

I don't think it has to do with the density change as much as the yeast being chilled, going dormant, and settling to the bottom of the fermenter. All that protein and trub is already so much more dense than the beer, that it will settle out over time. But I think the movement of the yeast towards the bottom probbaly helps accomplish this faster.

This is all conjecture, based on my limited experience with cold crashing.

 

[duboman]

Well, first off, it's beer not water...

Yes, the clod crashing forces the yeast cells to drop out of suspension and in the process the protiens, hop debris and anything else is forced out of suspension as well during the process which is why cold crashing is a common practice in clarifying the beer. The longer you go, the clearer the beer basically but keep in mind that there is still enough yeast in suspension to properly bottle condition and carbonate.

Think about making a lager and the amount of time a beer is spent lagering at 32-34 degrees and how a great lager is a beautiful crystal clear beer

 

[noob1979]

Well, first off, it's beer not water...

Obviously, you haven't had my beer.




Sent from my iPhone using Home Brew

 

[noob1979]

Now that I have time to think about your comment, duboman, it makes a lot of since. I have heard on HBT there are some that will crash for 5+ days. Does anyone know of a maximum optimal length of time for ale vs. lager yeast? I'm a biology teacher, and have a tendency to over analyze a bit, so stop me if I overstep here. I really am awed by the wealth of communal knowledge here.
Cheers


Sent from my iPhone using Home Brew

 

[BigFloyd]

I can only speak from my anecdotal experience, but I normally crash the primary for 5-7 days at 35-36*F. It clears the beer nicely and causes the cold yeast cake to be more firm. Having plenty of beer on hand, I'm in no rush.

 

[passedpawn]

Intuitively, I assumed that the yeast remained buoyant due to their respiration. While warm, they are constantly metabolizing sugars into alcohol and CO2. Both of those are less dense than water. With a bit of those inside their cell walls, they stay in suspension.

When they get really cold, they stop metabolizing sugars, stop creating CO2 and alcohol, and thus the gas is let out of their balloon. They drop due to their relative density.

I'm not a biologist and I made all that up. So, consider that before you repeat or believe any of it.

 

[Thedutchtouch]

I had a whole long response typed up and my browser crashed and lost it. Grr. Shorter version here:

Beer is a colloid, meaning a fluid that has particles in suspension. When the fluid is cooled, the molecules enter a less excited state, meaning there is less vibration in atomic bonds, and less movement overall within the fluid (less molecules hitting each other and bouncing off in new directions, and those that do are moving slower). The slower the motion of a particle/molecule/whathaveyou, the greater the perceived effect of gravity. Meaning, though gravity is a constant, it makes a slower thing fall out more quickly than a faster one.

Secondly, yeast form flocs naturally, but also as a reaction to stress. Cold temperature=stress. Flocs fall out of solution more readily than single cells because their movement is hindered on a cellular level due (to being clumped) and also becausethe force of gravity has a larger pull on a larger mass than a smaller mass (law of universal gravitation). The differences in mass between a yeast cell and a floc, however, may be too small relative to the mass of the earth for this to make a noticeable difference.

Thirdly, a colder solution is more viscous. The frictional forces felt by yeast etc moving through a more viscous solution are higher, resulting in overall slower movement of molecules within the fluid, which gets back to the first point.

Finally, fermentation is a turbulent reaction, both due to the creation of by products (CO2) causing turbulence as the molecules literally move through the fluid, and also because fermentation is an exothermic (gives off heat) reaction. Thermo- Fluid dynamics are a whole different post, but basically, putting heat into a fluid causes molecules to move, and more movement=greater turbidity.

 

[Gameface]

 

[noob1979]

Great information folks.

Gameface. Is that a yeast collection, or a before pic?


Sent from my iPhone using Home Brew

 

[duboman]

Great information folks.

Gameface. Is that a yeast collection, or a before pic?


Sent from my iPhone using Home Brew

That appears to be a time lapse video of a starter clearing as the yeast flocculates out of suspension

 

[noob1979]

Oh, cool. It didn't register as a video on my phone.


Sent from my iPhone using Home Brew

 

[Gameface]

Great information folks.

Gameface. Is that a yeast collection, or a before pic?


Sent from my iPhone using Home Brew

It's a gif of a yeast starter after being pulled off a stir plate. There are 9 images taken 20min apart.

 

[noob1979]

I was able to get it to work. Nicely done.


Sent from my iPhone using Home Brew

 

[noob1979]

I was watching the Big Secue make apple jack and he used something that wine makers do to clear the apple jack. That would kill the yeast in the fermenter, yeast I use to carb up in the bottle. Folks here use Spanish moss or gelatin for flocculation. Would gypsum work as well, or is that a little too dangerous? I know you are able to get suspended clay out of a pond with the stuff, and it is calcium carbonate, I don't know if there are any acids in beer that would react with it and create carbonic and hydrogen.


Sent from my iPhone using Home Brew

 

[Gameface]

I was watching the Big Secue make apple jack and he used something that wine makers do to clear the apple jack. That would kill the yeast in the fermenter, yeast I use to carb up in the bottle. Folks here use Spanish moss or gelatin for flocculation. Would gypsum work as well, or is that a little too dangerous? I know you are able to get suspended clay out of a pond with the stuff, and it is calcium carbonate, I don't know if there are any acids in beer that would react with it and create carbonic and hydrogen.


Sent from my iPhone using Home Brew

I think gypsum would greatly alter the taste of the beer.

 

[noob1979]

Ok, I haven't put anything in a secondary. I do however want to know, if I go from crashing a primary, to a bottling bucket, and crash in the bucket, would that have a great effect on the clarity? I may just be beating a dead horse with that.
Cheers

 

[JimRausch]

Gelatin works well in conjunction with cold crashing. The cold crash starts the precipitation and the gelatin speeds the process and helps make a nice compact layer on bottom. I usually cold crash in the 30-40* range for 24-48 hours, add gelatin, and leave it for another couple days before bottling.
Gypsum is Calcium Sulfate. It is used during an AG mash to acidify the mash and add additional sulfate. It will definitely change the flavor. As an experiment, pour a beer and add 1/8 tsp. It won't hurt you, and you can see what the flavor change is. And I'm pretty sure it won't help precipitate anything anyways.

 

[rpe290]

I was watching the Big Secue make apple jack and he used something that wine makers do to clear the apple jack. That would kill the yeast in the fermenter, yeast I use to carb up in the bottle. Folks here use Spanish moss or gelatin for flocculation. Would gypsum work as well, or is that a little too dangerous? I know you are able to get suspended clay out of a pond with the stuff, and it is calcium carbonate, I don't know if there are any acids in beer that would react with it and create carbonic and hydrogen.


Sent from my iPhone using Home Brew

Calcium carbonate is "chalk" -Gypsum is Calcium sulfate. Either would be added to the mash/boil for pH/flavor, not for clearing later on.

Spanish moss is something that grows on live Oak in the South --maybe you meant Irish moss, and that is also a boil kettle addition.

Maybe you meant bentonite? used in wine more than beer I think.

Gelatin and Polyclar should be in your brewing toolbox for post boil clarifiers.

 

[Thedutchtouch]

For a 5 gala batch I use half a tab of whirlfloc thrown in for the last 5 min of the boil, ferment in a bucket with no secondary, then after fermentation is done, transfer to a keg, add one pack unflavored Knox gelatin (remember to let it bloom first). After a few days, I pull off a cloudy pint or two, and the rest of the keg is clear enough to read HBT through a full glass. Good enough for me.

 

[capt82]

noob1979,
How much change did you have cold crashing it at 35-40*? That's the temp I have in my uncontrolled refrigerator.

I ask because I messed up a 3 gallon California Common and it looks like mud. I was debating cold crashing it to see if I can clear it up some, but others say it could kill the yeast. My understanding is the yeast will go dormant in the cold and wake up again after bottling.


Sent from my iPad using Home Brew

 

[noob1979]

I went from sludge to a full body feel. I started with a floating mat of hops though and it fell inside 24 hours. It's not clear by any means, but I wasn't really looking for perfect clear, I prefer unfiltered beer. I would say it decreased the floating particulates by half. I only crashed for four days though. Longer would have been better. I'm thinking about the Gelatin idea with the crash. I have a batch BIAB dry hoping right now. I didn't put gelatin in it though either. Tomorrow will be day five for that and I will crash it for a week. To see what the difference is. I have been carbing the bottles for 6 days now, they are getting tension in them, PET, all I added was corn sugar. I have the 750ml bottles.

I am concise ring using 2L bottles for mini kegs. The article I saw here was very inspiring. Does anyone know if I should try to extrapolate the sugar volume per bottle or just calculate for 2.5 gal and add before bottling? I would assume make a 3/4 cup sugar to 1cup water syrup and use half.

I'm learning a ton from everyone here. Mostly that my terms and procedures are not there yet, but I'm hopeful. Keep up the good work guys.


Sent from my iPhone using Home Brew

 

[noob1979]

I realize the gravity of a new beer can change during dry hoping. Am I to assume this is unfinished fermentation, or did I add some sugars with the hop addition.
My OG was 1.047, FG before the addition was 1.014. Five days of dry hoping in a bag and FG of 1.012.
I took the bag out, should I leave it for a couple of days, or will I loose too much flavor?


Sent from my iPhone using Home Brew

 

[worthogg]

You're not introducing any sugars when you dry hop. It's most likely your yeast just continuing to chew down that final couple gravity points. I usually dry hop for three to five days. I've been led to believe that almost all the aroma and flavor extraction is complete in well under a week.

 

[noob1979]

Thanks. The hops seemed pretty spent when I removed them.


Sent from my iPhone using Home Brew

 

[BigFloyd]

If you dry hop for too long with certain hops (Cascade comes to mind), you can get some pretty pronounced grassy notes. 3-4 days should get you the aroma you seek w/o the grass.

 

[noob1979]

Thanks, I used Millennium. I will keep that in mind.


Sent from my iPhone using Home Brew