Yeast attenuation in Recipe Editor

[AHarper]

This is a general question to all. It is based on my experiences and is subject to the many errors I make while brewing.

Have you noticed that the Final Gravity, and therefore the final ABV, rarely matches the values laid out in the recipe?
By that you can set up a recipe in the editor and select your yeast from the drop down. The %Attenuation gets input from the selected yeast data - it is usually an average value (the partial cause of the problem) - and it can be edited to what ever value you want. As you change this value the Final Gravity and ABV values alter accordingly, but what value SHOULD you use?
The Original Gravity may come out as the recipe suggests if you have a good mash regime and the temperatures are correct during the mash. Being a couple of points out is normal and not a serious problem. The Final Gravity is a different matter.
There are many factors than can affect the performance of the yeast. The number of cells in the pitched yeast - dry form or starter - the temperature of the atmosphere around the fermenter and the type and make of the yeast. I do not know if light plays any factor but it might - has anyone looked at this?

Anyway, I have used several different yeasts for different types of beers and faithfully used the recipe builder to map out the expected values - rarely did the end results and values match the plan exactly. The variation in the Attenuation value always seems to be the deciding factor. Most of my beers have been fermented in an InkBird controlled fridge in an effort to give some stability to the process but there is more drift than I am happy with. How do commercial brewers do it consistently?

I decided to take a look at some values from brewed recipes and the exported Fermentation results. I use Tilts to track the fermentation process and all these results so I can assume the FG values are accurate (?) and the other values are taken from the recipe design. There are two Attenuation values. One is from the Yeast attenuation value in the recipe and the other is the calculated value using the fermentation results.

The question is why do I consistently (?) get very high Attenuation compared to the selected - admittedly average - value of the yeast as published? This is usually at the upper end - and sometimes well past it. Do I now use this far higher, determined, value in future brews or stick to the manufacturers published average?

What do others do? What would you do? Has anyone else looked these types of figures?

I am fed up making a head belter beer when I swore to the wife then next one will be a mild, easy drinking lager she can handle.

 

[Megary]

Some of those attenuations are off-the-charts high for the yeast used. I’ve only used S-04 twice and I think I got low 70’s. I don’t want to suggest anything nefarious going on in your equipment, but you must be making the most fermentable wort of all time. Do you use a lot of sugar in your recipes? Mash low and long? Ferment warm? There’s a lot that can influence attenuation.

 

[Pricelessbrewing]

You'll also get different attenuation for a given recipe based on the mash temperature, fermentation temp, the yeast pitch rate, the OG, and the grains used.

Otherwise, S04 going up to 94% and US05 up to 91% is a more serious issue. If I didn't know you, my first thought would be contamination and having some kind of saison or otherwise diastatic yeast in the there, unless the recipe had a significant amount of simple sugars added.

 

[AHarper]

Some of those attenuations are off-the-charts high for the yeast used. I’ve only used S-04 twice and I think I got low 70’s. I don’t want to suggest anything nefarious going on in your equipment, but you must be making the most fermentable wort of all time. Do you use a lot of sugar in your recipes? Mash low and long? Ferment warm? There’s a lot that can influence attenuation.

Hi,

Yes I know some of the figures seem ridiculous I agree. For instance this is my Punky Munky fermentation chart - done by tilt so that may be out by a couple of degrees but it was still high atten.

I have had a couple of pretty low FGs and this was one of them. Nothing special in the recipe if you want to look at it.
https://www.brewersfriend.com/homebrew/recipe/view/1016685/punky-munky
It was a puzzle.
There are many in the low to mid 80's and I can live with them.

 

[AHarper]

You'll also get different attenuation for a given recipe based on the mash temperature, fermentation temp, the yeast pitch rate, the OG, and the grains used.

Otherwise, S04 going up to 94% and US05 up to 91% is a more serious issue. If I didn't know you, my first thought would be contamination and having some kind of saison or otherwise diastatic yeast in the there, unless the recipe had a significant amount of simple sugars added.

Yes there are many reasons I agree. I have few beers that had any contamination issues - except in the early days of course - and as I mentioned to Megary, the Punky Munky came out pretty good with no issues - except for the figures, and you know what I am like with Exports!!!

This is still work in progress and I will try and tighten up on my tilt calibration etc but it looks like I generally do better than the average quoted attenuation values. A puzzle but I will crack it eventually. I was just wondering if anyone else had similar observations.

 

[Megary]

For your next few beers, maybe confirm your tilt FG readings with a hydrometer, just to make sure??

 

[Donoroto]

Careful using a tilt for FG. Krausen krud atop the capsule will affect the readings.

 

[Sunfire96]

Careful using a tilt for FG. Krausen krud atop the capsule will affect the readings.

My incorrect tilt FGs are always too high, never too low

 

[Donoroto]

Mine are often low. Dunno, but it definitely tells me when sg is stable...

 

[AHarper]

Mine are often low. Dunno, but it definitely tells me when sg is stable...

Yes that is how I use them. I'll drink the beer whatever the FG turns out to be,

 

[Ozarks Mountain Brewery]

I don't even measure anything any more, I just brew it and drink it

 

[J A]

I definitely wouldn't assume that the measurements are right with those numbers. S-04 or US-05 consistently in the 80s is believable but those figures just don't add up. Rather than assuming everyone else in the world gets lower attenuation and yours is magically higher, I'd look at the measuring device. If you're not confirming these figures with a hydrometer, they're likely just not correct.

 

[dmtaylor]

This is excellent documentation of just how inaccurate the Tilt can be for FG measurements. Not much beyond that.

 

[Josh Hughes]

This is excellent documentation of just how inaccurate the Tilt can be for FG measurements. Not much beyond that.

Mine is within a point or 2. So much that I no longer double check.

 

[AHarper]

I definitely wouldn't assume that the measurements are right with those numbers. S-04 or US-05 consistently in the 80s is believable but those figures just don't add up. Rather than assuming everyone else in the world gets lower attenuation and yours is magically higher, I'd look at the measuring device. If you're not confirming these figures with a hydrometer, they're likely just not correct.

No magic here just puzzlement. I just wondered if anyone else had looked into the data.

 

[Sunfire96]

Alan, I haven't myself seen such discrepancies between predicted and actual FG. I agree that some of your equipment might need to be checked and recalibrated. What kind of thermometer do you use to check your mash temp? What device are you using to check gravtities?

The yeasts that I use most often will sometimes stray from the average attenuation listed. For instance I tend to get 78% out of S04 instead of 75%, but it's almost always the same amount.

 

[Donoroto]

This got me thinking, and so I dug out all my records and, of those complete enough to tell (most of them) it seems that i am getting mostly lower attenuation than the recipe prediction. Some of the recipe attenuations are manually entered.

Red is lower, green is higher, gray is mostly neutral

I suspect my lower attenuations are from my tendency to ferment a bit cooler. But after a couple of days I do warm it up several degrees, so I dunno. I am not too concerned about it though.

 

[AHarper]

This got me thinking, and so I dug out all my records and, of those complete enough to tell (most of them) it seems that i am getting mostly lower attenuation than the recipe prediction. Some of the recipe attenuations are manually entered.

Red is lower, green is higher, gray is mostly neutral

View attachment 19473

I suspect my lower attenuations are from my tendency to ferment a bit cooler. But after a couple of days I do warm it up several degrees, so I dunno. I am not too concerned about it though.

No I'm not too bothered either - a beer will be what a beer wants to be - Shakespeare got it wrong in Hamlet!!!

 

[J A]

No magic here just puzzlement. I just wondered if anyone else had looked into the data.

I use Tilts to track the fermentation process and all these results so I can assume the FG values are accurate (?)

I think the first place to look is your assumption that your values are accurate. Not at all a safe assumption. Since you don't have hydro readings to verify those figures, they don't mean anything and should be ignored until you can get real data.
I think you're asking the wrong question... "Why is my FG so much higher than predicted?" should be "Since I'm getting readings that don't look at all right, what is my actual FG?"

 

[Mark Farrall]

No magic here just puzzlement. I just wondered if anyone else had looked into the data.

I've got a few recipes where I consistently get over or under the predicted average number. After a few batches to confirm that it is different enough and it wasn't something I want to change, I'll adjust the yeast attenuation. 90% of the time, though, the numbers are close enough that I don't change anything.

My black IPA and a few of my mixed fermentation Saison's are the ones that get a different attenuation. And the main reason I change is so that I've got a reasonable guideline for when to spund, or dry hop, or some similar late stage process step.