Attenuation?

[hilljack13]

I have noticed that my attenuation is all over the place. I only use dry yeast and most of that is S-04/05. My last three were with S-05. One was a big beer that had 82.6% attenuation, 10%abv. My current brew which is almost done fermenting, is sitting at 70% and no movement in almost two days. It is sitting till Thursday at a minimum. Prior to that I was at 73%, (6.55%abv) so decently close. I also had a stout I used S-05 with that went 80% at 8.4%abv.

What can cause such fluctuations? I am using a 500g pack so the batch is the same and it sits in the fridge until ready to use. I did measure out a bunch of 11.5g packs that I sealed for easier use.

I am just trying to get more consistency if that is even possible. Thanks!

 

[day_trippr]

Both the beer recipes and the mash temperature profiles used matter when it comes to attenuation.
Are these beers close in those regards?

Cheers!

 

[hilljack13]

I used the same temperature to mash. Either 152 or 153F. The big beer had something like 22lbs of grain and the efficiency was ~65% if I remember. IIPA. The other two were clone ale's and should have been around 5.5%abv, but they had higher efficiency (still working on that). At least those two were close, I think.

If it matters, the IIPA was pitched with three yeast sachets, the current was with two due to the higher than expected OG. I can't remember the other ale. Pretty sure the stout was with two sachets.

 

[Erik the Anglophile]

Post grainbills for the recipes so we can see if they were influencing your attenuattion.

 

[Erik the Anglophile]

And how do you measure temperatures? I had similair issues a while back, turned out my thermometer was really unreliable and I invested in a decent quality digital one.

 

[worlddivides]

I've also wondered why attenuation can fluctuate so much. Brewing software will suggest I'll have 1.007, but I end up with 1.010. Brewing software will suggest 80% attenuation, but I get 75% attenuation. And that's with mashing at 149F or 150F for an hour and getting a higher starting gravity than the software estimated. I am aware that attenuation for a yeast strain is just a range, but sometimes I'll overpitch by quite a bit and still only get 75% attenuation with US-05, although Fermentis has their apparent attenuation range for US-05 as 78% to 82% (I do think I've gotten higher than 82% from 05, though). Even if I know the main factors that contribute to attenuation, it's still kind of a mystery as to why I can get anywhere from 70% to 85% from the same yeast with a highly fermentable wort.

In short, I'm just as curious as the OP.

 

[Cheshire Cat]

This is what I do, the numbers are from the brews I’ve made using the above yeasts, which are mainly repacks of branded one I.e Midland = Nottingham, Five = US05 etc. The bottom line is the average the I put into my recipes.

Yeast Actual Attenuation

Midland	Five	Hell	Pia	M31	Clipper	M54
78%	83%	89%	81%	83%	81%	79%
76%	85%	83%	83%	87%	83%	81%
77%	82%	91%	85%	85%	80%	77%
80%	84%	79%	83%			79%
84%	84%		75%			81%
84%	83%					79%
76%	83%					80%
76%	86%					80%
77%	81%					76%
81%	83%					83%
80%	83%
82%	83%
75%	84%
74%
79%
82%
79%	83%	81%	81%	85%	81%	80%

 

[corncob]

Pitch rate doesn't effect attenuation in my experience, except that a drastic underpitch might result in incomplete fermentation.

When the wort is boiled, the content of all the various species of saccharides is set. Any given yeast strain will ferment the various sugars to various degrees pretty reliably and repeatably, unless they can't finish for some reason. That's really an "incomplete fermentation" and will result in off flavors.

The attention you get from most ale yeasts can be made to vary 10-15% by manipulating mash temperature, in my experience.

Things to check:

1. Your thermometer. Calibrate it in boiling water and ice water.
2. Your crush. Whatever it is, it must be the same every time. The finer the crush is, the faster conversion will proceed at dough-in BEFORE your mash temp is stabilized. So given the same recipe and strike water temp, you can get about a 5% change in attenuation just by varying the crush, give or take.
3. Your hydrometer. Calibrate by making up sugar solutions at approximate starting and finishing gravities.

Other than those 3, it's all about doughing in the same way every time, controlling temps to within about 2deg (especially at the start of the mash), measuring temps the same way every time, and taking good notes. I think it's not uncommon to be able to predict attention on one's own system to within 2-3 points for a new recipe/new yeast. You should be able to hit it within a point for a new recipe/familiar yeast. Give or take.

 

[hilljack13]

Post grainbills for the recipes so we can see if they were influencing your attenuattion.

My current brew (fermenting)
78.4% Pale Malt - Extra Pale 10.000 lb
17.6% Crystal - 75L (2-Row) 2.250 lb
3.9% Caramel/Crystal Malt -120L 0.500 lb

IIPA
89.9% Pale Ale (2-Row) 20 lb
4.5% Corn Sugar 1lb
3.4% Carapils 0.75 lb
2.2% Carastan 0.50 lb

Stout
88.6% Pale Malt (2-Row) 15.5 lb
5.6% Chocolate (2-Row) 1.0 lb
2.9% Crystal - 60L 0.50 lb
2.9% Carafa II 0.50 lb

Temperature is regulated by the G40 internal. I have measured with a calibrated digital thermometer and it is within 1F at boiling temps.

 

[Erik the Anglophile]

20+% of crystal is a heck-load of crystal, I wouldn't be surprised by a low AA for that one...
Is the G-40 recirculating the mash? I mash in a cooler bag but always stir it before taking the temp to get an accurate reading, try stirring the mash a bit then take a temp reading.

 

[scrap iron]

Your first recipe has a lot of crystal malt at 21%. That is a contributing factor.
Looks like Erik bet me to the post.

 

[dmtaylor]

21.5% crystal malt could affect attenuation in a big way.

Crush and calibration are also likely factors as others had mentioned.

 

[mac_1103]

I am just trying to get more consistency if that is even possible.

Unless you brew exactly the same recipe in exactly the same way several times with different results, you really can't say that the attenuation is inconsistent.

 

[worlddivides]

2. Your crush. Whatever it is, it must be the same every time. The finer the crush is, the faster conversion will proceed at dough-in BEFORE your mash temp is stabilized. So given the same recipe and strike water temp, you can get about a 5% change in attenuation just by varying the crush, give or take.

That's one thing I never considered. I think that's probably a big part of it. I've only ever considered the crush in regards to mash efficiency, not in regards to apparent attenuation.

 

[hotbeer]

Very minor point of contention...

They don't make S-05. It's US-05. They do make S-04 though. And not a US-04.

 

[hilljack13]

Is the G-40 recirculating the mash?

Yes, it has a silicone tube that recirculates from the bottom pump and "stirs" the top of the grain bed.

I've only ever considered the crush in regards to mash efficiency, not in regards to apparent attenuation.

The stout was crushed on hand mill. The others with the Spike mill. I'm still trying to get that crush size right.


The current brew is the Pizza Ports Shark Bite Red Ale

 

[day_trippr]

At this point the real question is how could one expect consistent results with all these variables wandering around?

Cheers!

 

[hilljack13]

I guess I would just like to see more "consistency" to what is advertised. I haven't been brewing long enough to understand some these aspects. I just know that people say to pitch more on big beers and one should be enough on said gravity. I only input 75% to these apps and recipes.

 

[mac_1103]

I guess I would just like to see more "consistency" to what is advertised.

What is advertised for S-04 is 74-82%, which is quite a range if you think about it. US-05 is advertised to be a little less variable at 78-82%. But attenuation depends on both the wort and the yeast. So for example, if 25% of your OG is in the form unfermentable dextrins then you're never going to get 80% attenuation (unless you use a diastatic yeast). OTOH, if you have a very highly fermentable wort with a very low percentage of dextrins (say because you mashed low and the recipe includes sugar or syrup) then it's possible to exceed the yeast's nominal attenuation range. To pick an extreme example, either one of those strains will give you 100% attenuation if you add glucoamylase to the fermenter.

If you want consistent attenuation you have to make consistent wort.

 

[corncob]

If you want consistent attenuation you have to make consistent wort.

This is what I was trying to say with all those words up above. S-04 has an advertised attenuation of 74%-82%, but an experienced brewer with good notes and reliable instruments and a stable process can easily make a wort that it will attenuate 68% or 85%, and also predict the attention within about a point.

 

[pvtpublic]

Are you controlling your fermentation temperature? If so, how?

 

[hilljack13]

Are you controlling your fermentation temperature? If so, how?

Spike Flex+ and glycol chiller.

 

[hilljack13]

What is advertised for S-04 is 74-82%, which is quite a range if you think about it. US-05 is advertised to be a little less variable at 78-82%. But attenuation depends on both the wort and the yeast. So for example, if 25% of your OG is in the form unfermentable dextrins then you're never going to get 80% attenuation (unless you use a diastatic yeast). OTOH, if you have a very highly fermentable wort with a very low percentage of dextrins (say because you mashed low and the recipe includes sugar or syrup) then it's possible to exceed the yeast's nominal attenuation range. To pick an extreme example, either one of those strains will give you 100% attenuation if you add glucoamylase to the fermenter.

If you want consistent attenuation you have to make consistent wort.

I'm still trying grasp some things but I think I see what you mean. Other than the Pale Malt in the above, most of the grains are different so I should expect different outcomes? I don't really plan to brew the same thing soon so all this may be a mute point.

 

[hilljack13]

This is what I was trying to say with all those words up above. S-04 has an advertised attenuation of 74%-82%, but an experienced brewer with good notes and reliable instruments and a stable process can easily make a wort that it will attenuate 68% or 85%, and also predict the attention within about a point.

I had to go back an re-read. From your three points, I can say I check all the boxes. Since I am new to most of the brewing world, I still have some issues. Trying to figure out what I need to change is becoming a challenge, even when I follow advice from the multiple questions I keep asking. I don't know, something just isn't clicking. I feel I am close, but missing something. No way I can come close to predicting if I'll get 68% or 85% attenuation.

For clarity
1. Your thermometer. Calibrate it in boiling water and ice water. - Checked with ice water and boiling water, only when reaching boiling temps does the thermometer vary ~2deg from the G40 probe.
2. Your crush. Whatever it is, it must be the same every time. The finer the crush is, the faster conversion will proceed at dough-in BEFORE your mash temp is stabilized. So given the same recipe and strike water temp, you can get about a 5% change in attenuation just by varying the crush, give or take. - Currently using Spike mill set at 0.045. Only change was for 1 gal batches which aren't part of this discussion
3. Your hydrometer. Calibrate by making up sugar solutions at approximate starting and finishing gravities. - Check twice and same with refractometer. Hydrometer always reads .002 high.

 

[mac_1103]

most of the grains are different so I should expect different outcomes?

Short answer is yes. I don't know what software (if any) you're using or how it handles mash temps and yeast strain. I just use the free Brewer's Friend recipe builder, which doesn't seem to do much in terms of adjusting for mash temps and just plugs in a single number for yeast attenuation. It would make a lot more sense to think of both fermentability and attenuation as ranges.

 

[corncob]

If you want to be able to predict attenuation, you'll need to either use brewing software or build a little spreadsheet (my choice) or do some math by hand.

Base malt attenuates more than crystal, which attenuates more than dark malts, etc. Sugar always has an apparent attenuation of over 100%. You have to add everything up. And then tweak your model based on your results.

 

[Yooper]

Ingredients play a great role in yeast attenuation, simply because some ingredients are fully fermentable (simple sugars), some less so but still fermentable like base malt with a lot of maltose for the yeast to 'eat', and some far less fermentable (crystal malts, roast malts) and some mashes will favor a wort with more maltotriose (a higher mash temp, for example) and will be less fermentable. As a rule, yeast will prefer simple sugars first, and then the last sugars will be more complex like maltotriose.

So there is a lot going on in the mash with ingredients that play a bigger role in yeast attenuation than choice of strain or temperature.

 

[BrewnWKopperKat]

FWIW, steeping & pasteurizing (no need to boil) a small wort (perhaps .25 gal) that contains a single crystal (perhaps 60L) or roasted (perhaps chocolate) is both easy and informative. Measure OG (refractometer), pitch some yeast (room temperature above 65F is fine), and let it ferment.

I've done this with either 60L or chocolate a couple of times using US-05. Steeped, 60L is fermentable (lower FG than OG, but definitely not 80% attenuation). Steeped, chocolate malt does not appear to be fermentable at all (FG = OG in two trials, so effectively 0% attenuation).

Adding enzymes to the steep (just 60L or just chocolate) at 155F could be one approach for 'simulating' a mash - and perhaps a modern take on the "Testing fermentability of crystal malt" topic from the late Nov 2010 here at HomeBrewTalk.

 

[ba-brewer]

I used the same temperature to mash. Either 152 or 153F. The big beer had something like 22lbs of grain and the efficiency was ~65% if I remember. IIPA. The other two were clone ale's and should have been around 5.5%abv, but they had higher efficiency (still working on that). At least those two were close, I think.

If it matters, the IIPA was pitched with three yeast sachets, the current was with two due to the higher than expected OG. I can't remember the other ale. Pretty sure the stout was with two sachets.

How do you determine when to stop mashing?
It is better to calculate an estimated target gravity and measure for when it gets close then to simply go by time.

 

[day_trippr]

fwiw, I was fortunate to have plenty of time during my latest brew so I decided to track the mash SG in near real time. I extended the mash duration until the SG stopped climbing - which was almost an extra 45 minutes for a 5 point rise vs my usual 60 minute mash.

BUT the resulting OG was indistinguishable from the exact same recipe using my "normal" mash process and duration - which includes a rise from 150° F to mashout at 170°F (~10 minutes) and a stand of another 10 minutes before I start the runout - which takes another 45 minutes at 1 qt per minute for 11 gallons to the kettle. I've brewed that recipe 3 times before and the OG is always 1.074 - as was this batch. Basically I hit the same number earlier in the process.

So...an interesting exercise. My take-away is to just do what I always do and keep the basic mash duration at 60 minutes as my crush seems compatible


Cheers!

 

[hilljack13]

How do you determine when to stop mashing?
It is better to calculate an estimated target gravity and measure for when it gets close then to simply go by time.

I haven't gone a far as to do an iodine test. I just know that when I did a 60 min mash, my SG was usually 5+ points lower than what pre-boil expected. When I started doing 75 I am usually a point or two. Obviously, I am still learning.

 

[ba-brewer]

I use a refractometer to measure the gravity during the mash, I normally only get to about 90% of the expected gravity at a temp in the 150-154F range, the final 10% happens when I raise the temp to 164F. Not exactly sure why but sometime getting to 90% takes longer than 60min so I extend my mash until it gets there.

 

[IslandLizard]

I use a refractometer to measure the gravity during the mash, I normally only get to about 90% of the expected gravity at a temp in the 150-154F range, the final 10% happens when I raise the temp to 164F. Not exactly sure why but sometime getting to 90% takes longer than 60min so I extend my mash until it gets there.

Interesting...!
What kind of mash system do you use?

How finely/coarsely is your grist milled? Coarser milled grist may take longer to obtain full conversion.
Have you tried mashing longer at 150-154F to see if that (simply) raises your gravity too?

 

[hilljack13]

Interesting...!
What kind of mash system do you use?

How finely/coarsely is your grist milled? Coarser milled grist may take longer to obtain full conversion.
Have you tried mashing longer at 150-154F to see if that (simply) raises your gravity too?

Same question. I do a mash out for 10 min. I haven't checked gravity before the mash out. Maybe I should just to see where I am at.

 

[MicroMickey]

Any control of the degree of attenuation should be made during mashing, and not by attempting to adjust matters subsequently.

 

[ba-brewer]

Interesting...!
What kind of mash system do you use?

How finely/coarsely is your grist milled? Coarser milled grist may take longer to obtain full conversion.
Have you tried mashing longer at 150-154F to see if that (simply) raises your gravity too?

I have a RIMS system. I condition my grain to a get a fairly course crush and preserve the husks, allows for a quicker flow without compacting the bed. I think my mill it set to .04 or so.

I have done extended mashes but it seem like there is a plateau at about 90%, sometime I hit that level as early as 40mins but let it run to 60min and it does not increase gravity until the temp is increased.