Hi Bart,
All of this is my opinion, and it would be especially beneficial to hear from other forum members.
It sounds like you have continued fermentation in the bottle. Leaving them on the shelf can develop into a very risky and dangerous situation. There is the possibility of continued and more intense gushing and potential injury from exploding bottles. Exploding bottles in the market could be a liability for the brewery. None of those are desirable.
So what happened to cause the situation? Basically, fermentable substrate has been added to beer that contains a whole range of microorganisms in addition to Saccharomyces cerevisiae. Those microorganisms can ferment more than just glucose, maltose, and maltotriose. They can ferment dextrins remaining in the beer, as well as other substrates, and they can also produce additional CO2.
You mention beer going into whiskey barrels that have been previously used for beer and it developed a pellicle. Assuming this is wood, there can be a whole range of yeast, including Saccharomyces wild yeast, non-Saccharomyces yeast, and bacteria remaining in the barrel. Some of the organisms can ferment sugars and dextrins that Saccharomyces cerevisiae cannot ferment. The by-products of these fermentations are then used as fermentable material for some other organism in the barrel. In short, there is an entire ecosystem inside the barrel and each individual organism can thrive once the conditions are favorable and those conditions are constantly changing during barrel aging. In this continuous change, there is always a condition that is just right for some particular organism to begin fermentation. This is one reason why barrel aging is so interesting and, if all goes right, can produce some fantastic beers.
Then the beer was transferred to another tank where yeast (Saccharomyces) and fruit (sugar source for yeast) were added. Depending upon the type of fruit used, it can also bring more microorganisms into the beer The beer was held for 7 days. Afterwards, the beer was transferred to a CCV and held for 21 days. Then priming sugar was added, with a target calculation of 2.5 v/v CO2, and the beer was bottled.
Most likely, there is more fermentable substrate remaining at packaging than calculated. Target CO2 was calculated based on the idea of no other fermentable sugar remaining AND only Saccharomyces cerevisiae in the package.
There is the possibility that Saccharomyces (English ale yeast), non-Saccharomyces (Brettanomyces?), bacteria (pediococcus?), along with some remaining fermentable sugar and dextrin carryover from the beer, in addition to the priming sugar, went into the package. Coupled with possible oxygen uptake at transfer and filling, all of this helps to support continued fermentation. It takes place more slowly than a primary fermentation and this new fermentation takes place in the closed container. It looks like the beer was packaged in March and now, 2 months later, you have gushers.
It is quite possible that the gushing will continue to intensify to the point of becoming dangerous.
What to do in the future?
For the gushing, pasteurization is probably the best option. You will inactivate any organism that is fermenting and there will be no more risk of continued fermentation in the bottle once it is out in the marketplace. Pasteurization levels will probably need to be higher than what is needed for a standard lager, for example. Packaging members of the forum can certainly give some feedback.
Sterile filtration could also be a possibility, but beer will need some type of pre-filtration before running through a sterile filter.
Keg only and sell from the brewery. Keep the product cold until point of dispense. This, however, only offers a limited protection against further fermentation as well as limited selling opportunity.
If you decide to continue packaging as is--not recommended--you need to use bottles that can withstand higher internal pressure, such as a champagne bottle, but this still does not stop continued fermentation, gushers, and possibility of explodig bottles.
Look at a beer sample under a microscope and also plate some samples to examine the micro growth. It always helps to identify what you are dealing with in order to fix the problem. If you have no in house lab, there are probably labs nearby that can do this work for you.
Finally, keep the production equipment and production areas for these types of beer separate from any standard production beers. The organisms that grow in barrels can easily spread and contaminate the rest of the brewery. That is a situation to be avoided at all costs.
Always happy to talk further.
Cheers!
Andrew
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Andrew Fratianni, Dipl. Brew.
Sr. Enzyme Application Specialist
Brewing & Distilling Enzymes
IFF Health & Biosciences
andrew.j.fratianni@iff.com------------------------------
Original Message:
Sent: 05-26-2022 11:33
From: Jason Weihbrecht
Subject: Overcarbing of fruit beer in bottle: origin and solution?
Sometimes this can be caused by the fungus Fusarium that produces hydrophobins, which cause gushing. It's usually a problem associated with barley and hops, but I don't see why it couldn't have possibly on the fruit that was added.
Have you checked the CO2 content in the package to check if it has increased by some refermentation in package? You could also check things like ABV or AE to see if there are signs of unintended fermentation.
As for next time, I definitely would make sure to clarify the beer as much as possible to minimize anything that could act as a nucleation site for CO2 to break out.
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Jason Weihbrecht
Lab Manager
Oskar Blues Brewery
Brevard NC
Original Message:
Sent: 05-25-2022 08:50
From: Bart Ferguson
Subject: Overcarbing of fruit beer in bottle: origin and solution?
Hi all,
We're puzzled by a bottled fruited barrel-aged barleywine, that had fermented out and was stable in the tank but produces a subtle gusher when opened.
We brewed a barleywine in November 2020 (SG 1.102), let it ferment out (FG 1.030), racked it to a whiskey barrel previously used for a beer. In the barrel the beer developed a pellicle. A year later (Feb '22) we racked it to a blending vessel, added blackberries and fresh english ale yeast, and left it for seven days. Then we pushed it into a CCT, let it clear for 21 days (FG 1.030). After that period we bottled it, with priming sugar to yield 2.5 vol CO2, using equipment that we use to bottle funky/sour/diastatic/everything beers. This month (May) the bottles are gushers (FFG 1.028). They are not bottle bombs or vulcanoes, but they are way too 'enthusiastic' to our taste. We're thinking of keeping them on the shelves for a bit to see if that reduces the gushing (perhaps settling of nucleation sites?). Have you had similar experiences, and did you do something that reduced the gushing later?
Thinking ahead to a next batch, is there something we could do to prevent it next time? We think it's gotten plenty of time to ferment out and have particles of the fruit settled and removed in the tanks. Could it be the restarting of the yeast in the bottle? Could it be an infection - very well possible but then how long would you leave it after fruiting?
Best wishes, and thanks,
Bart
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Bart Ferguson
Utrecht
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