Sour Beer - temperature related?

I've been having a curious problem with my beer lately: all but one of my last 6 batches has developed a sour taste within a few weeks. The strange part is that I brew 10 gallon batches with my dad, and after primary we split it into two five gallon kegs, one of which stays with him and the other goes home with me. His half of our batches has not been going sour.

I'm familiar with lactobacillus infections and take great care to sanitize everything thoroughly. Before our last brewing session, I took apart every single keg I own and and cleaned each piece with a B-T-F chemical (I'm forgetting the name--it comes in a bottle designed similarly to that of iodophor but I believe it's an acidic solution) and I always sanitize with iodophor before putting beer into any keg. My lines and picnic faucets are always soaked in iodophor before tapping the kegs.

The only difference is storage: his kegs are always refrigerated, but my beer fridge died recently so I've been forced to keep my kegs unrefrigerated for the last several months. During the end of the summer and early fall, I kept my kegs in my pantry where the temperature is 68-70 degrees, and since temperatures have been dropping, I've kept my last two batches in the garage where temperatures range from 45 - 55 degrees. Without fail, every batch I've taken home and stored unrefrigerated has developed a sour taste within a few weeks (and it has been extra foamy, like it's infected). Three batches ago, however, I opted to put my batch of fresh-hopped IPA into three gallon kegs. My wife was gracious enough to let me use up half of our refrigerator in the house to keep the beer cold, and that batch did not develop a sour taste.

I'm thinking that the temperature has to be the issue since it's essentially the only variable, but would temperature alone cause the beer to turn sour or are the higher temperatures promoting growth in an inherent bacterial infection?

Thanks for the help,

Isaac

sour taste is most likely from a lacto bacillus infection in your keging system. its quite obvious you are missing something somewhere with your sanitation ... my guess is the non-metal parts. could be your o-rings, or beer lines. its possible you have had this problem all this time but never noticed because the beer fridge kept the bacillus from growing.

MAJOR EDIT: I just re-read and realized your problem was POST-primary. Kept my original post below in case it gives you any ideas. New response is that yes, probably temperature. The cooler fridge temps would keep the lacto from thriving. Has your dad tried not refrigerating one of his kegs to see if it develops a sour flavor? If it does, then you're introducing lacto during the brewing process, and if it doesn't then it's likely something with your kegging process. Either way, it's probably been tamed previously by the cooler temperatures. If you can figure out where the bacteria is getting introduced then you can prevent it from souring with or without refrigeration.

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If there were a bacterial infection already present in a beer, a higher temperature would make it more likely that the bacteria would thrive (especially lactobacillus). But I don't think there's a bacteria presence during your brewing process because your dad's batches aren't developing a sourness even after they're bottled, warmed up, etc. It seems like the bacteria must be getting introduced somehow where you are stashing the fermenters. If you've always been fermenting them in the fridge prior to this, then it would be too cold for the souring bacteria to really survive in the fridge, so I think it's an environmental issue now and not just a temperature issue.

Where was your dead fermentation fridge located versus where your currently keeping the fermenters?

What's the problem? Sour beer is the next big thing!

Sorry, I don't have anything constructive to add other than that.

Thanks for the responses! One weak link might be our fermentation vessel. We clean it and then sanitize it with iodophor every time, but we haven't taken it completely apart and sanitized all of the parts. It's a 15 gallon keg, so taking apart the in- and out-fittings and sanitizing them thoroughly certainly wouldn't hurt. We'll do that today before our latest pale ale goes in for primary.

It's worth taking apart your fermentation vessel, but don't forget to take a hard look at whatever you are using to rack into the kegs. I agree with the others though, the low temps are probably inhibiting the souring bugs in your dad's kegs.

Check and clean your CO2 equipment and pay particular attention to the gas disconnect and the supply line. These are often overlooked and if there is any bacteria in either, it will be injected directly into the beer any time you force carbonate or add CO2 to the keg. The regulator itself could become contaminated if beer somehow manages to back up into it for whatever reason. Cool temperatures would certainly slow down the bacteria growth, but that is not the source of the infection.

I'm starting to agree with the temperature thing, as the cause for souring. Here is what I have run into. I brewed a Westy12 clone, that was fabulous for well over a year, and it has been in a keg since racking from the secondary. I just tapped off a few glasses and it has a sour taste to it. Needless to say, I am severely pi$$ed off about it. My kegs have been in the basement the whole time too. so temp must be the only thing. Because if it was a sanitation issue, I think it would have soured long before. I am at a loss to explain this. The only other thing I can think of is the CO2. Is it possible for beer to sour because of the CO2 ????

Bombo80 said:

I'm starting to agree with the temperature thing, as the cause for souring. Here is what I have run into. I brewed a Westy12 clone, that was fabulous for well over a year, and it has been in a keg since racking from the secondary. I just tapped off a few glasses and it has a sour taste to it. Needless to say, I am severely pi$$ed off about it. My kegs have been in the basement the whole time too. so temp must be the only thing. Because if it was a sanitation issue, I think it would have soured long before. I am at a loss to explain this. The only other thing I can think of is the CO2. Is it possible for beer to sour because of the CO2 ????

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Read my previous post. It's not likely the CO2 itself is source of the contamination, but more probably the gas line, keg connectors or the regulator. Warmer temperatures could well accelerate the growth of any bacterial or wild yeast infection, but it would not be the source IMO.

Bombo80 said:

My kegs have been in the basement the whole time too. so temp must be the only thing. Because if it was a sanitation issue, I think it would have soured long before.

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That is not necessarily true. If it sat untouched for a year in your basement how do you know it turned sour? Sour is caused by bacteria or wild yeast.

I know the recent sour taste is something that has occured just recently. I have sampled this beer periodically, just for a change of pace beer. I haven't had a glass for probably 3 months. I usually make sure the keg is pressurized well, then remove all the lines. I think the next thing to look at, and sanitize and sgterilize is all the gas lines and serving lines.

I don't know about temps in the seventies, but I`ve stored kegs a cellar temps of 50-55F for a year with no problems what so ever.

Well, I disassembled all my CO2 and tap lines. I picked up a bottle of BLC (beer line cleaner) and soaked everything in that for an hour or so. When I was taking the CO2 lines apart, I found that one had some beer in the line. I think this happened when I force carbed a keg, at some time in the past. I didn't have any issue until just recently. I guess I just got lucky. The bad thing is I have about a half keg of a strong dark Belgian ale, that now has a sour taste. I'm not sure what to do with it. I might try to blend it with another beer (from bottles) to see if that helps cut the sourness. I hate to dump it. I will try this blending and hope I don't get sick from it. So far none of the sour beers I have, (and I have three kegs) have made me sick to this point. I am trying to finish them instead of dumping them.