Help needed for gushing...

[sembola]

I am trying to use one of the traditional produce of Italy (where I live), the chestnut . It had an very important role in feeding mountain populations until 1950s, and it is used by some craft breweries, sometimes as an ingredient , sometimes in the boil to give some flavours.

So I have brewed a chestnut ale twice, both times the beer was pretty good but both times in some three months it became overcarbonated and produced "nice" beer fountains. The first time I thought i had an infection, so I uncorked all remaining bottles and called it a lesson learned (though I tasted one and it seemed fine).

I tried again, and the same thing happened. One month of maturation and it's tasty, three months and you get a fountain. It's not impossible I managed to mess up two brews, but no other beer gave me problems whatsoever. Maybe there is a flaw in the specific procedure...

Grist is 75% pale malt, the rest is Munich, Biscuit and SpecialB. The chestnuts have been boiled and peeled, then squashed and kept in water at 60°C for 1 hour to fully gelatinize the starch; I have used 1/4 by weight of the grist. Mashed grains and chestnuts at 64°C for 45' and 72°C for 30', one hour boil, hopped at 29 IBU with EKG/Styrian Golding, pitched S-04 and fermented at 18-19°C for 16 days, then cold crash three days, fining with gelatin and finally bottled. OG was 1060, fermentation was monitored with a Brewbrain Float and it was completed in 10 days but I waited 6 days more, FG (measured with a traditional floating hydrometer) was 1016.

This time I didn't dump the beer but I measured the gravity (after degassing...) and it was 1007. So 9 points of further fermentation which can easily explain the fountains... I tasted it and it seemed normal, no strange taste or smell.

The only difference with my other (nearly 60) brews is the use of chestnuts, so I'm trying to understand what is wrong.

Maybe the gelatinization was not complete and some (a lot?) of starch remained unconverted. But how can unconverted starch become later edible by yeast?

Maybe I got an infection two times in the same beer (the only difference is the first brew was sparged, the second was BIAB). But can an infection only produce gas and not any funny/strange/different taste or smell?

Can anybody give advice?

Thanks in advance!

 

[day_trippr]

Greetings, @sembola, and welcome to the forums at Homebrew Talk

Unprocessed chestnuts contain a load of starch - and the enzymes to break that down into sugars when conditions are right. I would be curious about the denaturing temperature of the glucoamylase enzymes contained in chestnuts and whether the saccharification potential truly goes to zero in the course of brewing. Something to study up on

[edit] My wife and I visited Siena many years ago and greatly enjoyed the experience, and I had a thought just now that perhaps the altitude lowered the boiling point of wort significantly enough to perhaps allow some percentage of glucoamylase to survive the boil. But the city proper is around 1100 ft or 335 meters ASL, which would lower the boiling point of water to just a tiny bit below 99°C, which doesn't seem likely to be significant wrt denaturing glucoamylase...

Cheers!

 

[sembola]

Unprocessed chestnuts contain a load of starch - and the enzymes to break that down into sugars when conditions are right. I would be curious about the denaturing temperature of the glucoamylase enzymes contained in chestnuts ...

I don't even know if there are (and how much) enzymes in raw chestnuts, but having cooked them for 20 minutes I think there's none left anyway: I think 4 times malt should have plenty of diastatic potential.

[edit] My wife and I visited Siena many years ago and greatly enjoyed the experience, and I had a thought just now that perhaps the altitude lowered the boiling point of wort significantly enough to perhaps allow some percentage of glucoamylase to survive the boil. But the city proper is around 1100 ft or 335 meters ASL, which would lower the boiling point of water to just a tiny bit below 99°C, which doesn't seem likely to be significant wrt denaturing glucoamylase...

I didn't thought about altitude, but I agree it seems unlikey altitude can play a factor.

 

[mac_1103]

While I suppose that it's possible for some chestnut enzymes to survive your gelatinization and mashing steps, it seems highly unlikely that they would survive a one hour boil. But if your gravity dropped 9 points in the bottles then there had to be fermentable sugars left when you bottled. What temperature did you ferment at? Maybe try a few days at a higher temperature after fermentation seems to be done. Did you use a diastatic yeast by any chance?

 

[IslandLizard]

FG (measured with a traditional floating hydrometer) was 1016.

This time I didn't dump the beer but I measured the gravity (after degassing...) and it was 1007. So 9 points of further fermentation which can easily explain the fountains...

That proves the beer keeps fermenting (in your bottles).
1.016 is also pretty high for a 1.060 OG beer, fermented with S-04.

Although fermenting at 18-19°C for 16 days using S-04 may suffice for many regular beers, your chestnut addition may have changed that.

As @mac_1103 said, when fermentation is slowing down, raise it a few degrees to 21-22°C for another week and then recheck the gravity. If it has changed give it another week at the same (higher) temps, and so on, until your readings are stable (not changing anymore).
I have an inkling that your chestnut ale probably isn't done fermenting until you hit 1.007, or perhaps even a few points lower...

BTW, you must be using very strong bottles to contain that much pressure (from a 9 point gravity drop) without them exploding!

 

[mac_1103]

fermented with S-04

Sorry, missed that the first time.

 

[DuncB]

One point that I haven't seen mentioned is whether any priming sugar was added to the bottles?

Another option would be to use a less efficient yeast such as Windsor, this can't metabolise maltotriose.

 

[sembola]

That proves the beer keeps fermenting (in your bottles).
1.016 is also pretty high for a 1.060 OG beer, fermented with S-04.

Although fermenting at 18-19°C for 16 days using S-04 may suffice for many regular beers, your chestnut addition may have changed that.

As @mac_1103 said, when fermentation is slowing down, raise it a few degrees to 21-22°C for another week and then recheck the gravity. If it has changed give it another week at the same (higher) temps, and so on, until your readings are stable (not changing anymore).
I have an inkling that your chestnut ale probably isn't done fermenting until you hit 1.007, or perhaps even a few points lower...

BTW, you must be using very strong bottles to contain that much pressure (from a 9 point gravity drop) without them exploding!

In other brews I raised the temperature to complete the fermentation but not in this one, since I have used S-04 other times and I never got more than 76% AA, so 73% wasn't particulary suspect: I have got up to 88% only with diastatic yeasts (BE134, WB06 -but not always...). Anyway this is a possibile explanation and a temperature raise could be a prudent addition when I will try again.
I used belgian bottles weighing around 250g each.

One point that I haven't seen mentioned is whether any priming sugar was added to the bottles?

Another option would be to use a less efficient yeast such as Windsor, this can't metabolise maltotriose.

Yes, I added sugar at bottling, my notes say 6g/L.

 

[DuncB]

Thanks, could add some yeast nutrient and 7mg of Zinc to help the yeast during the primary ferment. Boost the temp as the ferment shows it's tailing off on the floaty, don't wait for it to be flatlined for days before this.
Do a fast forced ferment with a sample of the beer separately this should guide you to what the final gravity will really be and you potentially if you get the maths right could leave the sugar out of the priming.

https://www.winning-homebrew.com/forced-fermentation-test.html

 

[sembola]

Thanks, could add some yeast nutrient...

I forgot to tell, i added some of that too at the end of the boil (and moss too). Small qty as per producer instruction (5g/hL, so 0,5g for 10L).

Do a fast forced ferment with a sample of the beer separately this should guide you to what the final gravity will really be and you potentially if you get the maths right could leave the sugar out of the priming.

https://www.winning-homebrew.com/forced-fermentation-test.html

That's another good idea to consider.

 

[Beermeister32]

On the practical end of things, this might be one that is hard to determine. In that case, use empirical evidence - it keeps foaming/ fermenting for 3 months, otherwise good. Time for a workaround.

I’d be inclined to let those chestnut Ales age out for 3 months in a room temp corney keg and naturally carbonate if you have kegging capacity. Keg it, hose off the keg then put it away for a while, go move on to other things.

After 3 months, check the carbonation level in the beer. If over carbonated, vent it off a bit, and put in your keg rotation on tap.

 

[Hoochin'Fool]

You could try making an extract: maybe roast them on an open fire in your oven to be sure there's no enzymes left in the nuts, then grind them up and soak them in vodka for a few weeks, then add the extract at bottling time.

 

[sembola]

You could try making an extract: maybe roast them on an open fire in your oven to be sure there's no enzymes left in the nuts, then grind them up and soak them in vodka for a few weeks, then add the extract at bottling time.

Do you think boiling for 30 min. besore mashing and then 1 hour boil couldn't do that?

Anyway, roasted chestnuts in late boil or even smoke dried ones are used by some breweries to give a slight smoked/roasted aroma.

 

[kevin58]

On the practical end of things, this might be one that is hard to determine. In that case, use empirical evidence - it keeps foaming/ fermenting for 3 months, otherwise good. Time for a workaround.

I’d be inclined to let those chestnut Ales age out for 3 months in a room temp corney keg and naturally carbonate if you have kegging capacity. Keg it, hose off the keg then put it away for a while, go move on to other things.

After 3 months, check the carbonation level in the beer. If over carbonated, vent it off a bit, and put in your keg rotation on tap.

I like this solution. If it still over carbonates you can just bleed off the excess CO2.

 

[Hoochin'Fool]

Do you think boiling for 30 min. before mashing and then 1 hour boil couldn't do that?

Not really, to be honest. But SOMETHING unique to your use of chestnuts is causing your beer to start refermenting in the bottle. How are you grinding the nuts? Maybe you're leaving chunks that are too big for the subsequent mash/boil to completely denature?

 

[SFC Rudy]

Are your bottles clean? I mean using a brush clean?

I had the same problem. Got lazy for awhile and thought rinsing after the pour was good enough. Beers were good for a month or so then I would start to get gushers. Cleaned them with a brush and was surprised at how dirty my cleaning solution got. Beer stone and other crap does build up over time.

 

[sembola]

Not really, to be honest. But SOMETHING unique to your use of chestnuts is causing your beer to start refermenting in the bottle. How are you grinding the nuts? Maybe you're leaving chunks that are too big for the subsequent mash/boil to completely denature?

I agree it is something unique to the use of boiled chestnuts (see later).
I have boiled them for about 30 minutes, then peeled and crushed with a blender. Mashed at 60°C/140°F for 30 min for starch gelatinization * together with some malt , then added rest of strike water and grist. Chestnut were about 18% of total fermentables.
So, if I understand well, your hypotesis is that some amylase still present in the boiled chestnuts survived 60 more minutes at 100°C and, after the fermentation (apparently) finished, transformed some unconverted starch into sugars that the bottling yeast used to boost carbonation.

* AFAIK gelatinization temperature for chestnuts is among 57 and 70 °C

Are your bottles clean? I mean using a brush clean?

I had the same problem. Got lazy for awhile and thought rinsing after the pour was good enough. Beers were good for a month or so then I would start to get gushers. Cleaned them with a brush and was surprised at how dirty my cleaning solution got. Beer stone and other crap does build up over time.

I'm pretty confident this it's not caused by poor bottle cleaning, in 60-odd brews i got this problem twice but only in the chestnut ale. I think it's rather something in the process...

 

[mac_1103]

So the chestnut amylases survive 90 minutes of boiling but then become inactive during fermentation and reactivate in the bottles? That's some serious enzymatic gymnastics right there. To my knowledge, chestnut amylases are not any more thermostable than barley amylases.

But if this is what is really going on then it's a two part problem - the enzymes aren't being fully denatured and the starches aren't being fully converted. So attack both - boil the chestnuts longer, mashout longer, boil longer, etc, but also mash longer or maybe mash the chestnuts separately with some exogenous enzymes. Do everything you can think of to reduce the possibility of putting either unconverted starch or active enzymes into your fermenter.

 

[MaxStout]

I'm thinking the enzyme angle needs more looking into. We brewers deal with a few common ones, but perhaps chestnuts contain something different, and enzyme that can withstand higher temps? If not, then you can rule it out

Maybe you could search for an agricultural university that has some knowledge of chestnuts. It's been an important part of food in your region. There might be a researcher who knows about it.

 

[DuncB]

Just pressure cook the chestnuts no natural enzymes can survive that.
If done for long enough, but I can't see why a chestnut would need an enzyme that heat tolerant

 

[sembola]

I'm thinking the enzyme angle needs more looking into. We brewers deal with a few common ones, but perhaps chestnuts contain something different, and enzyme that can withstand higher temps? If not, then you can rule it out

Maybe you could search for an agricultural university that has some knowledge of chestnuts. It's been an important part of food in your region. There might be a researcher who knows about it.

I searched in the scientific literature and I could only find that chestnut pulp contain some endogenous amylase enzyme and that its starch is somewhat more "resistant" to amylase action. So it doesn't seem impossible that some starch from the chestnut did not get converted and got into the beer, but it seems unlikely that an enzyme that denaturates over 75°C survives 1 hour boil.

So the chestnut amylases survive 90 minutes of boiling but then become inactive during fermentation and reactivate in the bottles? That's some serious enzymatic gymnastics right there. To my knowledge, chestnut amylases are not any more thermostable than barley amylases.

But if this is what is really going on then it's a two part problem - the enzymes aren't being fully denatured and the starches aren't being fully converted. So attack both - boil the chestnuts longer, mashout longer, boil longer, etc, but also mash longer or maybe mash the chestnuts separately with some exogenous enzymes. Do everything you can think of to reduce the possibility of putting either unconverted starch or active enzymes into your fermenter.

I agree.
Just wondering: even if starch reaches the fermenter and then finished beer, what can transform it into sugar? Amylase shouldn't be present, and yeast cannot digest starch.I've seen hop creep, but I believe it's transformation of dextrins, not starch...

 

[mac_1103]

I believe it's transformation of dextrins, not starch...

Perhaps those "somewhat resistant" starches are being (partially) converted to (large) dextrins.

 

[sembola]

Perhaps those "somewhat resistant" starches are being (partially) converted to (large) dextrins.

It could be, but by what? there is anything else (apart from amylase enzymes which seem unlikely to survive boil) that is able to convert starch into dextrins/sugars?

 

[DuncB]

Hop enzymes.
As per hop creep.

 

[sembola]

Hop enzymes.
As per hop creep.

Can they degrade starch also, and not dextrines only? That could be a explanation.
I didn't dry hopped though, I trew 1g/L at 10 minute and 1,4g/L at flameout of Styrian Golding.

 

[mac_1103]

there is anything else (apart from amylase enzymes which seem unlikely to survive boil) that is able to convert starch into dextrins/sugars?

I meant during the mash, but yeah, there still needs to be something else going on later.

 

[DuncB]

I think no dry hop, then no hop creep.

 

[Skeeter686]

I am trying to use one of the traditional produce of Italy (where I live), the chestnut . It had an very important role in feeding mountain populations until 1950s, and it is used by some craft breweries, sometimes as an ingredient , sometimes in the boil to give some flavours.

Are there any craft breweries near you that have experience with chestnuts? They may be willing to give you some pointers if you ask.