Help- puzzling overcarbonation issue

[sparker42]

Hi all,
I need some help. I am an experienced homebrewer and for the past 8 months every batch I make becomes overcarbonated in the bottle. Starts OK, but by 1 month in the bottle it is a glass of foam. After 15 min sitting in a glass it is degassed and fine to drink. Great head retention too! Too much, actually.
I brew all grain, 6 gallon batches.
Here's what I have checked.
1) priming sugar weight: varies depending on style by typically 100-130g DME dissolved prior to bottling. So I'm not adding too much sugar.
2) Complete fermentation: I wait until gravity has stopped dropping in the secondary (usually 2 weeks), then an additional week to be sure. It always matches my predicted final gravity (using Brewsmith).
3) Recipes that used to be fine are now overcarbonated.
4) I did an interesting test. If I compare my "stable", predicted finishing SG at bottling, with the measured gravity of an overcarbonated bottle (after opening, degassing and adjusting to room temp), the bottle gravity is about 5 points lower than at bottling (Note that is before priming sugar added at bottling compared with after priming sugar used in the bottle). Made me conclude I had some sort of bacterial bottle infection that was processing some components and increasing gas. So last batch I washed the bottles, then bleached them, then dishwasher heated them, then acid rinsed them in star-san. And the same for all the containers, tubing, siphons, etc. Guess what. Overcarbonated after 1 month.....
I am at wits end. There is no off taste, there is not too much sugar (I used calculators to adjust for CO2 present at bottling temp), I store the beer at 65 degrees, then chill in a fridge for a couple days before opening.
I don't know what else I can check?
WHAT AM I DOING WRONG? PLEASE?
Steve

 

[grampamark]

This sounds more like an infection than a carbonation problem.

You mention using DME for priming. Are you using the same lot of extract or getting new DME for each batch? Some folks buy DME in larger quantities to keep on hand for priming. Could yours be contaminated? Have you tried priming a batch with something else?

You also mentioned doing some serious cleaning before the last brew, but didn't specifically mention fermenters. Might buy a new bucket, they're cheap, just to try an alternative to the fermenter you've been using.

If all else fails-drink more beer. Use it up within the first month.

Mark

 

[sparker42]

Thanks Mark,
Two good points.
I only use DME for priming and starters, so could be, though I have used more than a single bag over the 8 months. Could try a straight dextrose.

On the fermenter, I do sanitize it too, but had considered that because the SG drops to a stable value that all the "metabolism" had finished. I have had this overcarbonation issue with a batch that sat in the secondary of 2 months.

But, your suggestions are easy to implement, so I'll give a try. Have you heard of an infection that would slowly increase gas pressure like that (malo-lactic?). Would be good to know if these symptoms are common and difficult to sanitize or could come through the fermenter undetected.

Thanks,
Steve

This sounds more like an infection than a carbonation problem.

You mention using DME for priming. Are you using the same lot of extract or getting new DME for each batch? Some folks buy DME in larger quantities to keep on hand for priming. Could yours be contaminated? Have you tried priming a batch with something else?

You also mentioned doing some serious cleaning before the last brew, but didn't specifically mention fermenters. Might buy a new bucket, they're cheap, just to try an alternative to the fermenter you've been using.

If all else fails-drink more beer. Use it up within the first month.

Mark

 

[Smellyglove]

Have you used var. Diastaticus yeast prior to this started to happen? Like Belle Saison or BE-256. They create a microfilm inside the bottles. If this it not cleaned properly what you are describing can happen.

From Lallemand:
Saccharomyces cerevisiae var. diastaticus strains are capable of utilizing some types of dextrins. Extra care should be taken to ensure proper cleaning procedures are in place to avoid any cross-contamination with other brews.

 

[AZCoolerBrewer]

Normally I wouldn’t think it, but what about something to do with the bottle caps. Maybe they were somewhere not so savory. Do you sanitize your bottle caps?

 

[flars]

You may have an infection or you are bottling before the fermentation is complete. Final gravity/attenuation estimates in Brewsmith(?) may be the same attenuation estimates given by the yeast manufacturers. These estimates are only for comparing yeasts produced by that manufacturer. The percentages are produced by fermenting a standard wort for all of the yeasts. Actual final gravity/attenuation is determined by the fermentability of your wort. You may be stalling the fermentation by taking the beer off the yeast in the primary or slowing it to the point the SG seems stable.

Try leaving you beer in the primary for at least three weeks to establish the final gravity. The beer will clear in the primary. Skipping the secondary will also reduce some oxidation and infection risk. Bottled beer that continues to drop in SG more than likely means more cleaning and replacing some of the equipment that can't be disinfected with confidence.

 

[jalc6927]

Clean the bottles directly after emptying them and make sure no gunk is left, than sanitize them better

 

[jalc6927]

Also, is it possible you’re using too much yeast?

 

[sparker42]

Awesome guys, thanks. Your are all pointing to an infection of some sort. Made me think more through my process. I had not used diasticus (on purpose anyway!), but could be it got in there. I typically did not sanitize caps, but have done so for the last few brews thinking that was a potential problem, but the other thing I have changed that you made me think of is I started using an air pump to oxygenate at pitching. I do sanitize the stone, but could be the filter is not sterile and I am getting something from the air directly into the wort. I'll rethink that and sterilize the entire system.
Thanks for the advice.
Steve

 

[pdxal]

Sounds like an infection.
I don't think anyone has mentioned bottling bucket or bottling hardware. Spigots in bottling buckets need to be taken apart to be sanitized effectively, and you might consider either changing all bottling gear or seriously bombing it with bleach and/or another sanitizing agent.