Why underpitching yeast is bad. Worst (almost) case scenario.

[NotSure]

I wanted to make a Baltic Porter to age for next winter and chose Wyeast 2206 Bavarian Lager to work with. In building my recipe, I was more concerned about the grist bill and admittedly not as much about the yeast apart from using the proper type. On brew day I was set with all my ingredients including two packs of Wyeast 2206. In hindsight, I wasn't thinking. This was using lager yeast, pitching cold, and high gravity at that. Two smack packs just ain't gonna cut it. I should have made a starter, but I was out of DME and got away with it before.

I brewed my Baltic Porter, pitched the yeast and got activity on the airlock in about 18 hours. So far, so good. The fermentation was going fine, or so I though. About eight days into it, the airlock noticeable slowed (a bubble every 9 seconds to a bubble every 20 seconds), so I started I increased the temperature slowly for a D-rest. The bubbling on the airlock went slower...and slower...and slower. It took three weeks for it to stop bubbling.

I checked the gravity and then checked it again a few days later. If you rounded up, it was right at the bottom of the indicated attenuation range. I used Munich as a base and also Amber, Caramunich and Carafa III, so this seemed right to me. I thought it was done. Then, I cleaned/sanitized the bottles and added the priming sugar and bottled. I tried the bottles at one week, two weeks, three weeks and noticed them getting progressively more carbonated. This was good, but week 3 was a bit more than intended.

On week 5, I decided to try another since (1) they tasted wonderful, (2) I had a lot of bottles, (3) I was a bit concerned about the carbonation. I popped one in the fridge and opened it a couple hours later.

BOOM! Beer all over the place. Got books, my keyboard, three walls and nearly hit the ceiling. I was stunned with a stupid look on my face. It took a day and a half to clean-up, but could have been worse. I use swing top bottles and have been relieving the pressure before putting them in the fridge. There were about 30 of them and this took time after an initial confrontation with PTSD.

I also gave a couple to a friend, who drank one and saved the other. Told him the story and the attached photo he sent me after he opened one of the bottles. The long and short of it is that the yeast stalled at the worst possible point.

I swear to God, Jesus, and cute little baby Jesus, that I will take the yeast pitch rate seriously from this point forward!

 

[rburrelli]

I am confused. Why would you assume that yeast underpitching would be the cause of the bottle bombs? You had fermentation activity in a reasonable amount of time. You likely bottled too soon but I can’t connect that to an ubderpitch.

 

[NotSure]

The yeast gave up and were moving so slow that I bottled. The taste was not off at all. I had gravity readings three days apart that were stable. Basically, the bottling process roused the yeast. They stalled at exactly the worst time. If it didn't underpitch, odds are I'd have enough yeast to finish the job without stalling.

 

[Twinkeelfool]

I am confused. Why would you assume that yeast underpitching would be the cause of the bottle bombs? You had fermentation activity in a reasonable amount of time. You likely bottled too soon but I can’t connect that to an ubderpitch.

I also think it appears it was bottled too early

OP what was the fg?

 

[Birrofilo]

The yeast gave up and were moving so slow that I bottled. The taste was not off at all. I had gravity readings three days apart that were stable. Basically, the bottling process roused the yeast. They stalled at exactly the worst time. If it didn't underpitch, odds are I'd have enough yeast to finish the job without stalling.

I don't know this particular yeast, but normally lager yeast has problems in working at higher temperature. At what temperature did you store the bottles?

The priming "rouses" the yeast, but only insofar as there is priming sugar to consume, normally.

I see you did the right thing, checking density for three days. Do you have your fermenter at constant temperature? In general, attenuation figures are unreliable in my experience, patience is more reliable. But I understand that, after three days with stable density at probable FG, bottling comes natural.

A mistake in priming calculations should not be totally excluded, though.

If you use sugar rather then dextrose, and put a too dense syrup in the beer, it will take a bit to be dissolved properly. Maybe your syrup was too dense and went straight to the bottom of the vessel, and some bottles are undercarbonated and some bottles are overcarbonated.

 

[NotSure]

I also think it appears it was bottled too early

OP what was the fg?

1.021 before bottling. I'm planning to get an actually FG after I let some of the bottles sit for a couple weeks.

 

[NotSure]

I don't know this particular yeast, but normally lager yeast has problems in working at higher temperature. At what temperature did you store the bottles?

The priming "rouses" the yeast, but only insofar as there is priming sugar to consume, normally.

I see you did the right thing, checking density for three days. Do you have your fermenter at constant temperature? In general, attenuation figures are unreliable in my experience, patience is more reliable. But I understand that, after three days with stable density at probable FG, bottling comes natural.

A mistake in priming calculations should not be totally excluded, though.

If you use sugar rather then dextrose, and put a too dense syrup in the beer, it will take a bit to be dissolved properly. Maybe your syrup was too dense and went straight to the bottom of the vessel, and some bottles are undercarbonated and some bottles are overcarbonated.

I was storing the bottles in a closet with a fairly stable temperature of about 18-20C (64-68F). For fermenting, I have a fermentation chamber with an inkbird. It spent about 8 days at 11-12C (52-54F) before ramping-up slowly over two days for D-rest at 16C (61F). It was still bubbling slowly, so I left it at this temp for 15 days. To encourage it to finish-up, I left it at room temp and a few days later the airlock stopped. 32 days total in the FV from pitching the yeast to bottling.

I'm fairly sure I got the priming sugar amount correct, but I agree there's always a possibility I didn't. I used Dextrose dissolved in boiling water, chilled to room temp and then added to the FV while stirring. All the bottles were massively overcarbonated.

After I let the remaining bottles sit a few weeks I'll get the actual FG and see where it sits.

 

[hout17]

How much priming sugar did you add and how much beer did you have in your bottling bucket? Just curious. Also what kind of sugar?

 

[NotSure]

How much priming sugar did you add and how much beer did you have in your bottling bucket? Just curious. Also what kind of sugar?

140g of Dextrose was used to bottle 47 500ml bottles. This should have given me about 2.3 Volumes of CO2.

 

[hout17]

140g of Dextrose was used to bottle 47 500ml bottles. This should have given me about 2.3 Volumes of CO2.

Yeah, you are right on the money I get right around 2.35 volumes plugging in the numbers.

This is an interesting case. I believe I saw you gently stirred your priming sugar in up above.

The only time I've ran into this issue is when I used to add in the priming solution to the bucket first and then let it mix with the beer as it transferred from the fermenter to the bottling bucket. I got a few bottle bombs that way. Once I started gently stirring that issue went away.

Definitely sounds like there were still some fermentables left. That probably would've caught me off guard too.

Edit: I've heard of this happening if some wild yeast or an infection find their way in but that's all I've got.

 

[NotSure]

Yeah, you are right on the money I get right around 2.35 volumes plugging in the numbers.

This is an interesting case. I believe I saw you gently stirred your priming sugar in up above.

The only time I've ran into this issue is when I used to add in the priming solution to the bucket first and then let it mix with the beer as it transferred from the fermenter to the bottling bucket. I got a few bottle bombs that way. Once I started gently stirring that issue went away.

Definitely sounds like there were still some fermentables left. That probably would've caught me off guard too.

Edit: I've heard of this happening if some wild yeast or an infection find their way in but that's all I've got.

I did initially think it may have had a bug and just to be sure I checked all my cold-side equipment. I didn't see anything and I've also done a few brews since the Baltic Porter and they had no issues. Cleaned and sanitized everything anyway just to be on the safe side. Also, the yeast started fairly quickly which usually is something positive with regard to keeping out bugs.

There's no off flavor at all, so if it's wild yeast then I'd think it'd be Saccharomyces cerevisiae v. diastaticus. I still have 8 bottles of the batch that I didn't put in the fridge and have bled almost all the pressure from them. I'll seal them up and let them sit for a few weeks and see if there's a pressure build-up. Once I think the yeast are done, I'll check the FG and taste. If the flavor is mostly gone and the FG is insanely low, then it's v. diastaticus.

 

[Toxxyc]

I'm going to say you bottled too soon, that's about it. Two packs of yeast, even pitched cold and into a higher gravity beer, should be fine. Also, you're lucky. You could have gotten hurt in the process. I carry scar from bottling too early.

 

[VikeMan]

Two packs of yeast, even pitched cold and into a higher gravity beer, should be fine.

Depending on the particulars, I don't agree with "fine." Here's why. This was a Baltic Porter, so let's assume 5 gallons (@NotSure please correct if wrong) and an OG right in the middle of the style's range, at 1.075. That's 18.2 degrees P. Using the (probably) most commonly quoted Lager pitch rate of 1.5M cells per ml per degree P, that's:

1.5M cells/ml/P x 18,927 ml x 18.2P = 516.7 Billion cells

2 packs of brand spanking new (which is doubtful) yeast would contain about 200 Billion Cells.

IMO, this would be a pretty serious under pitch for a lager. I have seen a similar situation where an underpitched lager crept along so slowly as to appear to give stable readings days apart. Fortunately, we realized what was going on and waited it out.

 

[NotSure]

Depending on the particulars, I don't agree with "fine." Here's why. This was a Baltic Porter, so let's assume 5 gallons (@NotSure please correct if wrong) and an OG right in the middle of the style's range, at 1.075. That's 18.2 degrees P. Using the (probably) most commonly quoted Lager pitch rate of 1.5M cells per ml per degree P, that's:

1.5M cells/ml/P x 18,927 ml x 18.2P = 516.7 Billion cells

2 packs of brand spanking new (which is doubtful) yeast would contain about 200 Billion Cells.

IMO, this would be a pretty serious under pitch for a lager. I have seen a similar situation where an underpitched lager crept along so slowly as to appear to give stable readings days apart. Fortunately, we realized what was going on and waited it out.

About 26 litres (with lots of trub) made it to the Fermenter and 23.5 litres made it to bottles. The batch was a bit bigger than 5 gallons. Also, my OG was 1.080.

 

[hout17]

His 47 500ml bottle number he gave me comes to about 6.2 gallons.

That's a huge underpitch though by your calcs vikeman wow.

 

[VikeMan]

About 26 litres (with lots of trub) made it to the Fermenter and 23.5 litres made it to bottles. The batch was a bit bigger than 5 gallons. Also, my OG was 1.080.

Yikes.
1.5M cells/ml/P x 26,000 ml x 19.3P = ~753 Billion cells

 

[Toxxyc]

Oi I missed that, sorry. Yes that would be a pretty big underpitch. I admit I underpitch often, but not by that much. My last lager I pitched around 350 billion into a 1.044 lager, right on the 5-gallon mark so it's a slight underpitch. I think I missed the large gravity, sorry.

 

[hottpeper13]

I always make a small beer as a starter for a high grav brew. I try to keep it under 1.048 OG

 

[Birrofilo]

@NotSure

I wasn't clear. My question referred to the temperature at which you store the bottles.

It is not unheard that fermentation can restart and yeast can begin, slowly but tirelessly, digesting complex sugars that they did not touch during the first fermentation. When this happens, it is a slow process, something that is noticed in months. The threshold between what is eatable and what is not is a blurry line and depends on time, temperature etc.

If we eat grain and supposing for some illness we have no enzymes to digest it, we would in any case digest it, slowly and "painfully", but ultimately we would digest it. Enzymes accelerate some chemical reactions, but that doesn't mean that those reactions wouldn't be possible without enzymes.

At the moment, though, the main suspect is an infection. Infections do not necessarily impart a "signature" taste or aroma.

 

[NotSure]

@NotSure

I wasn't clear. My question referred to the temperature at which you store the bottles.

It is not unheard that fermentation can restart and yeast can begin, slowly but tirelessly, digesting complex sugars that they did not touch during the first fermentation. When this happens, it is a slow process, something that is noticed in months. The threshold between what is eatable and what is not is a blurry line and depends on time, temperature etc.

If we eat grain and supposing for some illness we have no enzymes to digest it, we would in any case digest it, slowly and "painfully", but ultimately we would digest it. Enzymes accelerate some chemical reactions, but that doesn't mean that those reactions wouldn't be possible without enzymes.

At the moment, though, the main suspect is an infection. Infections do not necessarily impart a "signature" taste or aroma.

I store my bottles at 18-20C.

I'll know more as to if it's an infection or the underpitched Wyeast 2206 in a few weeks I hope!

 

[NotSure]

An update on this if anyone finds it of interest.... I bled the pressure from the bottles again in May by repeatedly opening and closing the swing-tops and finally letting them rest with the top off for a few hours. First took the gravity, then I let them sit a few weeks. After that, there was a little more carbonation, but not too much. The gravity stabilized at 1.013 (pictured).

I bottled three months prior at 1.021. Looking back at my notes, I did mash a bit low for a Baltic Porter, so 1.013 does sound reasonable albeit a bit high for attenuation.

Also, I happened to find a bottle that I missed for disposal/depressurization yesterday. After freaking-out a bit, I chilled the heck out of it, and opened it outside. It made a mess, but I saved 2/3's of it and it tasted good.

Assuming the priming added two points, the German swing-tops survived a 10 point change in gravity without exploding.