[Lazy Ant Brewing]

I have a beer fridge in the garage. 

If a bought a temp controller for it to control fermentation and used it both as a fermentation chamber and for storing bottled beer simultaneously, what would be the effect of the temperature cycling up and later down (after fermentation is finished) from say 40 F to 68 F on the beer that was being stored in there?

In other words, do I need to have a separate fermentation chamber and beer fridge, or can the fridge serve both functions at the same time?

Because of weight and medication issues I only drink 4 to 5 bottles per week, and I'm planning on brewing 2 1/2 gal batches so I can try new recipes more frequently. Thus some bottles in storage might go through several cycles of up and down temps in the process of fermenting new batches.

And one more question.  Would the freezer portion of that fridge still be usable with the controller manipulating
the temp of the fridge space?

Thanks in advance for your advice.

[mainebrewer]

Obviously, the beer would be better off without the temp swings. But, I don't know what the impact would be of several 30 degree temp swings.
As far as the freezer part of the 'fridge. It will maintain freezing temps at 40 degrees but not at 68.

[dmtaylor]

I don't think it matters all that much unless you have poor sanitization practices or known contamination issues, and as long as you always keep the temperature below 70 F as you plan to do anyway.  Temperature swings happen all the time in a distributor setting.  You wouldn't want to store the beer above that point for a significant amount of time as it will stale faster.  But if your average temp will be much lower than 70 F, you're still prolonging the life of your beer.  The alternative of course is to just drink it all within like 6 months of brewing, then you really don't need to worry.

[blair.streit]

I agree with dmtaylor's comments that it's probably not a huge deal.

That said, if I were worried about anything beyond contamination it would probably be oxygen ingress. Crown caps don't form a perfect seal, so minute amounts of oxygen are leaking into bottles all the time anyway.

I don't have any proof of this, but I would worry that 30F temperature fluctuations would create changes in pressure that would accelerate this process. Whether that acceleration would be enough of an issue to be concerned about I can't say, but since you mentioned storing the bottles for longer than 6 months in these conditions it's definitely something I would watch out for.

[Lazy Ant Brewing]

Regarding the increase in oxidation of bottles stored longer than 6 months, I guess time will tell. 

 I don't understand how oxidation occurs in bottled beer anyway, since the pressure in the bottle from CO2 would presumably be higher than atmospheric pressure.

Advice on that please and thanks for your previous comments.

[dmtaylor]

"They" will say that bottle caps allow oxygen ingress via osmosis.

Personally, I doubt that in most cases osmosis would allow so much oxygen ingress that it would cause appreciable oxidation in a span of a few months at proper storage conditions.  I believe most oxidation occurs due to the original oxygen present in the beer and in the fill space above it.  Osmosis seems a secondary effect that should take many years to have a huge effect.  Also... many (most? all?) brewers are using oxygen absorbing caps these days.  If those caps don't work, then well that kind of sucks and is false advertising, eh?

Besides..... canned beer goes stale as well.  Leave it sit for a couple years and I can guarantee that yes it does.  And there's no osmosis happening there.

In summary, I think oxidation occurs over long periods of time regardless of whether it's bottled or packaged in some other manner.

One thing I just thought of: Bottlers who are concerned about oxidation should probably be purging every bottle with CO2 prior to fill.  This is easy for keggers who have a CO2 tank.  Not so easy for bottlers but it could be done, and should if you want maximum storage life, say greater than 6 months like I indicated previously.

Personally, to some extent I kind of like the taste of oxidized beer anyway.  Gives it a little something.  The guys in the old days hundreds of years ago agreed with this as well, purposely blending new beer with stale beer to make it taste the way they liked.  They'd go 50/50 or 70/30 or whatever to give it that little something that they enjoyed.  I don't mind a little oxidation, especially in a stronger beer but even in a low gravity beer it's not so off-putting that I won't drink it.  So there's that too.  Taste is in the eye of the beholder like anything else.

[hopfenundmalz]

The law of partial pressures will cause O2 to go from the higher partial pressure in the atmosphere into the low partial pressure in the bottle, the pressure of the CO2 does not counter this. The diffusion through the cap liner happens,

Beer will stale under conditions of very low/no O2. There are redox reactions (reduction-oxidation), that result in staling. This is an electron exchange between molecules, the one that gains an electron is reduced, the one that loses the electron is oxidized.

[Visor]

Maybe I have too much skull where my brain should be, but I'm having difficulty understanding how atmospheric pressure could be greater than the pressure inside a sealed bottle of carbonated beer.

[dmtaylor]

Maybe I have too much skull where my brain should be, but I'm having difficulty understanding how atmospheric pressure could be greater than the pressure inside a sealed bottle of carbonated beer.

It can't.  However the laws of osmosis don't care as much about pressure differentials as the layman mind might imagine.

EDIT: I might be confusing the terms "osmosis" and "partial pressures" or maybe something entirely different.  It's been too many years since I've dealt with this stuff.  Somebody out there is smarter than me on this and knows the right stuff or will Google it.  Thanks in advance.

[Phil_M]

Yes, oxygen will enter the beer.

Will it matter?

Well, I had a fresh hop APA that I brewed sit on a shelf for a year. Bottle conditioned, O₂ absorbing lid. Shelf was at ambient temps (64-74, depending on the season.)

No oxidation flavors when I drank it a year later, and the fresh hop flavors were still there as well.

[hopfenundmalz]

Maybe I have too much skull where my brain should be, but I'm having difficulty understanding how atmospheric pressure could be greater than the pressure inside a sealed bottle of carbonated beer.

Look up Dalton's law of partial pressure. Sure the pressure in the bottle is higher, but the partial pressure of O2 is much lower.

Some have said the diffusion rate through a cap seal is around 1 ppb/day. When you consider that the best beers have a TPO of around 50 ppb or less, you can see the issue. The O2 will go up with time, the beer will stale. Sierra Nevada went to pry off caps to reduce the O2 ingress by about a factor of 20 - saw the graph at Ken Grossman's 2009 NHC keynote speach.

[Lazy Ant Brewing]

I have a friend that likes oxidized beers. 

He frequently encourages me to store a few bottles for a year or two.  He recently "shared" a 10-year-old bottle of home-brewed stout in a swing-cap bottle. A W F U L!!!![/size][/size]

He's a great friend, but I'm glad that was the last of his 10-year-old stash.