Consistently high attenuation / low FG

[lawst]

For some reason 90% of my brews end with an FG much lower than expected using the brewers friend recipe calculator. My OG is mostly bang on or at most a few points out but the FG is much lower than it should be.

For example my most recent brew was a Belgian blonde (all grain) with Mangrove Jack's M41 Belgian Ale yeast with an expected OG 1.057 and FG 1.007. There were no special sugars added, just grain. My actual OG was 1.058 and FG 1.005. The yeast attenuation range is 82-88% but my apparent attenuation was 91.4%.

An even more extreme example was an IPA with an expected OG 1.055 and FG 1.015. My OG was as expected but FG was 1.007. The yeast was WLP028 which has a 70-75% attenuation but I seem to have achieved 82.7%. This is one of my more frequent brews and I consistently get the same results.

From reading other forum posts and articles everything seems to point to an infection of some kind but the final product tastes good with no off flavours. I always give everything a thorough clean with PBW or sodium percarbonate and sanitise with starsan. I've stripped down all taps and components on my vessels, counterflow chiller and hoses from which I put all plastics in a chlorine solution initially then rinsed and added to a higher than normal concentration solution of starsan along with the stainless steel parts. I also replaced my silicone hoses. In other words everything the wort touches after the boil should be good to go.

I'm currently using a traditional 3 vessel all grain setup but had similar results previously with BIAB. I've also used different hydrometers and refractometers so I don't think there are any issues with my measuring equipment. I've checked temperature probes etc with multiple thermometers to ensure there are no issues with the mash temperature. I've only recently started doing water chemistry but that hasn't made any difference to the FG, only the flavour of the beer.

I'm completely out of ideas and although the beer is good, I'd like to have more precitable results. Is anyone able to shed some light?

 

[RPh_Guy]

I'm currently using a traditional 3 vessel all grain setup but had similar results previously with BIAB.

Tell us more about your brewing process...
What kind of mash schedule are you using?
You're making yeast starters?
Good oxygenation/aeration techniques?
Adjusting mash pH?
Possibly using yeast nutrients?
Are you adding enzymes of any kind?

 

[lawst]

Tell us more about your brewing process...
What kind of mash schedule are you using?
You're making yeast starters?
Good oxygenation/aeration techniques?
Adjusting mash pH?
Possibly using yeast nutrients?
Are you adding enzymes of any kind?

I brew a fairly wide variety of styles so the mash schedule varies but generally 65C/149F for 60 mins and then mash out at 76C/169F for 15 mins.

If I'm using liquid yeast I'll make a starter (like the IPA I mentioned) but with dried yeast I tend to direct pitch with no rehydration.

I'm not using any special aeration techniques, just creating a good amount of splashing when racking to the fermenter. I also recirculate while I'm chilling and the recirc port is above the wort in the boiler which also contributes to aeration.

I've been lazy with the mash pH until recently when I started doing water chemistry. I've been checking with pH strips and the pH seems to be within the expected range. Most brews require gypsum and calcium chloride but I also needed a bit of latic acid in the belgian blonde I mentioned to get the pH in the correct range.

I used to add yeast nutients towards the end of the boil but don't use them anymore. I also don't add any enzymes.

Hope that helps!

 

[dmtaylor]

M41 is diastaticus. Based on my own research it averages 93% attenuation, much greater than what you expected.

Diastaticus yeasts can cause permanent contamination, which could potentially explain your subsequent batches. Try replacing all plastic and rubber materials in your fermentation process and see if the problem disappears. Many people have found it necessary to dedicate two sets of equipment, one diastaticus and one not. Or one "wild" and one not, etc.

 

[RPh_Guy]

I think you're just seeing high attenuation because of high fermentability and healthy yeast.

65°C/149°F is pretty much the "sweet spot" for maximum attenuation from a single infusion mash, and pH adjustments help maximize enzyme activity.

Pitching healthy yeast (i.e. from a starter) also helps the yeast reach maximum attention.

If you simply want higher FG, I would consider mashing higher, around 68-71°C / 154-159°F.

Based on everything you've said, contamination seems less likely in my opinion. And I'm pretty sure "permanent contamination" isn't really a thing, otherwise no one could use a diastaticus strain on the main brewing or serving equipment. AFAIK, Belle Saison is the only commercial Saccharomyces strain that can form a biofilm, which can still be removed with proper cleaning.

How are you controlling fermentation temperature and what temperatures are you using? Higher temps may increase attenuation.

Welcome to HBT!

 

[lawst]

M41 is diastaticus. Based on my own research it averages 93% attenuation, much greater than what you expected.

Diastaticus yeasts can cause permanent contamination, which could potentially explain your subsequent batches. Try replacing all plastic and rubber materials in your fermentation process and see if the problem disappears. Many people have found it necessary to dedicate two sets of equipment, one diastaticus and one not. Or one "wild" and one not, etc.

Thanks for this, I'll look in to it further as its not something I'm familiar with. When you say fermentation process are you just talking about rubber washers etc in the fermenter itself or would it also include plastics etc in the boil kettle, chiller, ball lock taps? I'm wondering how far I need to take it.

 

[brownni5]

From my experience, the AA levels that the yeast companies cite are bunk, and so are the "expected FG" guesses that the brew software tell us.

A difference between 1.007 and 1.005? That's negligible. 1.015 to 1.007 is bigger, obviously, but if nobody told you, would you know? My guess is no.

Yeast is somewhat unpredictable - it's a living organism with a very quick life-cycle lending it to quick mutations. Trying to predict what will happen with your fermentations every time is likely to drive you nuts. Let me guess - engineer? Think like a biologist - let the organism tell you what they're thinking.

 

[lawst]

65°C/149°F is pretty much the "sweet spot" for maximum attenuation from a single infusion mash, and pH adjustments help maximize enzyme activity.

Pitching healthy yeast (i.e. from a starter) also helps the yeast reach maximum attention.

If you simply want higher FG, I would consider mashing higher, around 68-71°C / 154-159°F.

I forgot to mention I use a HERMs setup almost identical to the Electric Brewery and recirculate for the duration of the mash, although I'm not sure that makes much difference. It's a good point about increasing the mash temperature and its something I had planned to try with my next brew.

Based on everything you've said, contamination seems less likely in my opinion. And I'm pretty sure "permanent contamination" isn't really a thing, otherwise no one could use a diastaticus strain on the main brewing or serving equipment. AFAIK, Belle Saison is the only commercial Saccharomyces strain that can form a biofilm, which can still be removed with proper cleaning.

That's good to know I might not need to replace all my washers etc! I'll definitely look in to this more since its been mentioned twice and isn't an area I'm familar with.

How are you controlling fermentation temperature and what temperatures are you using? Higher temps may increase attenuation.

I'm using a temperature controller to ensure my fermentation temp is stable and I have a few different types so I'm confident there's no issues with the temperature or stability. I mostly ferment at 20°C/68°F and where I live the temperature is rarely more than the fermentation so I'm heating rather than cooling.

Welcome to HBT!

Thanks and I appreciate all the info you've provided

 

[lawst]

From my experience, the AA levels that the yeast companies cite are bunk, and so are the "expected FG" guesses that the brew software tell us.

A difference between 1.007 and 1.005? That's negligible. 1.015 to 1.007 is bigger, obviously, but if nobody told you, would you know? My guess is no.

Yeast is somewhat unpredictable - it's a living organism with a very quick life-cycle lending it to quick mutations. Trying to predict what will happen with your fermentations every time is likely to drive you nuts. Let me guess - engineer? Think like a biologist - let the organism tell you what they're thinking.

You guessed correctly!

 

[brownni5]

You guessed correctly!

Ugh. Engineers. A+B=C. Boring.

 

[dmtaylor]

Thanks for this, I'll look in to it further as its not something I'm familiar with. When you say fermentation process are you just talking about rubber washers etc in the fermenter itself or would it also include plastics etc in the boil kettle, chiller, ball lock taps? I'm wondering how far I need to take it.

Anything post-boil. So your chiller, HOSES (that's a big one), washers, o-rings, etc. But especially the fermenter itself, and hoses.

 

[ncbrewer]

There was a podcast on Master Brewers
http://masterbrewerspodcast.com/068-diastaticus-part-1 about diastaticus yeast. The link doesn't work now, but here are some notes I made:
Over-carbonation. Exploding bottles. Lawsuits. Super-attenuation caused by diastaticus contamination is a hot topic in the brewing industry. We bring you interviews with brewers, yeast suppliers, and independent microbiologists to talk about detection, prevention, and more. Whether your strategy is to keep diastaticus out of your brewery altogether or to manage it alongside other Saccharomyces cerevisiae strains lacking the STA gene, you're guaranteed to learn something from these interviews.

• Breaks down dextrin and causes bottle bombs
  
  
• Can be in the yeast (intentionally) or in the air
  
  
• There is no acceptable threshold - one cell can be a problem
  
  
• In 3 - 4 months, excessive carbonation. Another lab said within 2 weeks. Another tested bottles stored at 80F - went from 2.6 volumes to 3.7 volumes in 3 days
  
  
• Once in your brewery, it is everywhere
  
  
• Keep it at bay with good sanitation (apparently, this is for accidental contamination)
  
  
• If contamination, can tell within 2 weeks, or sometimes 1 - 2 months depending on how it is stored
  
  
• Be suspicious of any very high attenuationg yeast - it might include diastaticus
  

 

[RPh_Guy]

^ It's important to be aware of such things.

The yeast attenuation range is 82-88% but my apparent attenuation was 91.4%. [...] The yeast was WLP028 which has a 70-75% attenuation but I seem to have achieved 82.7%. [...] This is one of my more frequent brews and I consistently get the same results. [...] the final product tastes good with no off flavours.

All of this is why I believe it is not a contamination in this case.

I believe that a rampant diastaticus contamination would most likely reach closer to the same level of attenuation in every beer. I don't think it makes sense for the attenuation of a contaminant yeast to vary based on the pitched yeast.

If the high attenuation continues after increasing mash temp by 5-10°F, I think contamination would be a lot more likely at that point.

 

[brownni5]

Right, and just a few points above listed attenuation ranges. Diastatic yeast would take 75% AA to more like 90% or more.

 

[dmtaylor]

Fair enough dudes, you're likely correct.

Next thing then is to double triple quadrupel check your calibrations on your mash thermometer and your hydrometer. Be ABSOLUTELY CERTAIN you're hitting all your numbers, without any question at all.

 

[lawst]

Thanks for all the replies. Everyone seems to be in agreement its probably not diastaticus but I appreciate all the info about it. One of the great things with brewing is there's always something new to learn (or equipment to buy!).

Just to add to my original post, this has been happening for at least 3 years but maybe longer as my notes don't go back further than then. Generally the attenuation hasn't gone as high as 90% with the exception of the Belgian one I mentioned plus a Saison I did about a year ago so I guess this also reduces the chance of it being diastaticus based on what's been said.

Next thing then is to double triple quadrupel check your calibrations on your mash thermometer and your hydrometer. Be ABSOLUTELY CERTAIN you're hitting all your numbers, without any question at all.

I've done this a few times now as this is what I suspected the problem to be initially. I've checked the temperature reading with 3 or 4 different thermometers. They were all digital but different brands so even if there are inaccuracies I don't think it'll be out by much. I've also used 3 different hydrometers and 2 refractometers so I'm also confident about my measurements although I'll try this again on my next brew just to make certain.

If the high attenuation continues after increasing mash temp by 5-10°F, I think contamination would be a lot more likely at that point.

I'm brewing a milk stout this weekend that I've brewed previously so I'll increase my mash temperature and compare with the previous one to see what impact it has and report back on the results