FG 1.000 and Unfermentable Sugars

[SRJHops]

I've reached a point in my brewing knowledge where I'm confused about unfermentable/residual sugars...

For my last brew, a Belgian Blond, I mashed at 154 in order to try to create some residual/unfermentable sugars. The recipe software said I would hit 1.012 FG, but instead all the sugar fermented out and I hit 1.000. Not a huge problem to have -- my Blond became a Tripel! But I don't understand what happened to the unfermentable sugars?

The Belgian yeasts (I blended 3) were supposed to be moderately attenuative, but certainly not 100%.

Here are some factors that I think likely contributed to the 1.000, but I still don't understand what happened to the unfermentable sugars:

1. I tend to blend yeasts and it's very possible I overpitched. (I didn't use a pitching calculator.) Can overpitching alone cause 100% attenuation?

2. I mashed at 154, but for 90 minutes. The long mash likely created a more fermentable wort as the temp dropped a few degrees, but 100% fermentable?

3. I used a pound of table sugar to thin out the body and add ABV. (It was included in the recipe calculator.) I know sugar ferments out 100%, but again, what happened to the unfermentable sugars? Does sugar somehow accelerate fermentation so much that the yeast eats up the unfermentable sugar too?

Of course, I do know what to try next time, and I could do experiments: I could mash even higher, use less yeast, less sugar, and a shorter mash. But I want to understand what's going on, so I can better control my numbers. Thanks for any help you could provide.

 

[Barbarossa]

Alcohol has a lower gravity than water. You could have a .990 gravity liquid with .010 residual, totalling 1.000.

 

[VikeMan]

When you reach a Final Gravity of 1.000, that does not mean that there are no unfermentable dextrins left. 100% Apparent Attenuation is equal to about 82% Real Attenuation. The reason for the difference is that alcohol is less dense than water, so it makes the hydrometer reading lower than it would be without the alcohol. But, to get to your specific questions:

1. I tend to blend yeasts and it's very possible I overpitched. (I didn't use a pitching calculator.) Can overpitching alone cause 100% attenuation?

Overpitching doesn't cause more attenuation than pitching at a standard rate.

2. I mashed at 154, but for 90 minutes. The long mash likely created a more fermentable wort as the temp dropped a few degrees, but 100% fermentable?

Longer mashes do cause the wort to be more fermentable than shorter mashes.

Does sugar somehow accelerate fermentation so much that the yeast eats up the unfermentable sugar too?

No. But the simple sugar addition "by itself" will show an Apparent attenuation of about 122%. So that's certainly a factor in your overall apparent attenuation.

Of course, I do know what to try next time, and I could do experiments: I could mash even higher, use less yeast, less sugar, and a shorter mash.

Mash higher: Yes
Less Yeast: No
Less Sugar: Yes
Shorter Mash: Yes

Also, use less attenuative yeast strains.

ETA: Was one of your yeast strains a Saison strain?

 

[BrewChatter]

Sounds like on of the strains you used may have been diastaticus positive (which just means that they can break down unfermentable sugars), like a Saison strain such as 3711/Imperial Napoleon, which is what I think that @VikeMan may have been getting to. Given enough time, they will happily dry just about anything down to 1.000. I think he hit the nail on the head with using a less attenuative yeast strain for your next go at it.

 

[Vale71]

I doubt a yeast supplier would ever describe a diastaticus yeast as "moderately attenuative".

 

[SRJHops]

When you reach a Final Gravity of 1.000, that does not mean that there are no unfermentable dextrins left. 100% Apparent Attenuation is equal to about 82% Real Attenuation. The reason for the difference is that alcohol is less dense than water, so it makes the hydrometer reading lower than it would be without the alcohol. But, to get to your specific questions:



Overpitching doesn't cause more attenuation than pitching at a standard rate.



Longer mashes do cause the wort to be more fermentable than shorter mashes.



No. But the simple sugar addition "by itself" will show an Apparent attenuation of about 122%. So that's certainly a factor in your overall apparent attenuation.



Mash higher: Yes
Less Yeast: No
Less Sugar: Yes
Shorter Mash: Yes

Also, use less attenuative yeast strains.

ETA: Was one of your yeast strains a Saison strain?

Thanks! YES, I used Be-134, which is a Saison strain. Oddly, I have used it before with the same blend of slurries, and it did not attenuate all the way down to 1.000. BUT one other time it did -- on a Saison that I won a competition with. I didn't mind the 1.000 for that. But I'm trying to figure out why sometimes the same blend of yeasts attenuates down to 1.000, while other times it leaves me at 1.010 or a bit higher.

I really wanted to have my current Blond end at 1.012 or even 1.015, but I again got 1.000. It will hopefully still be a tasty beer, of course.

 

[SRJHops]

I doubt a yeast supplier would ever describe a diastaticus yeast as "moderately attenuative".

Sorry, I should have been more careful with my words.... The predicted average attenuation of the yeast blend was 80%.

Though the Be-134 (according to the recipe software in Brewer's Friend) had an average attenuation of 90%. So maybe I should have adjusted the calculator to 90%, but I'd have to enter 100% to get to 1.000.

 

[SRJHops]

Sounds like on of the strains you used may have been diastaticus positive (which just means that they can break down unfermentable sugars), like a Saison strain such as 3711/Imperial Napoleon, which is what I think that @VikeMan may have been getting to. Given enough time, they will happily dry just about anything down to 1.000. I think he hit the nail on the head with using a less attenuative yeast strain for your next go at it.

I think that must be it. I did not know that Saison yeasts always push that low. So, here's a question then. If I still want to use the Be-134, which I like, what should I do to stop it from fermenting the wort down to 1.000? Or is that not possible?

I used Be-134 (and slurries) for a tripel, dubbel, quad, and golden strong, and they did not ferment down to 1.000. But both my Saison and Blond did. I will need to go back to my notes, but I think the only big difference (other than grain bills) is that I mashed for 90 minutes for the Saison and Blond. I don't see how that made enough of the difference, but maybe so?

 

[Vale71]

Sorry, I should have been more careful with my words.... The predicted average attenuation of the yeast blend was 80%.

Mixing yeast strains doesn't work like that. The most attenuative strain won't "stop short" just because either less attenuative strains are in the mix.

 

[BrewChatter]

I think that must be it. I did not know that Saison yeasts always push that low. So, here's a question then. If I still want to use the Be-134, which I like, what should I do to stop it from fermenting the wort down to 1.000? Or is that not possible?

I used Be-134 (and slurries) for a tripel, dubbel, quad, and golden strong, and they did not ferment down to 1.000. But both my Saison and Blond did. I will need to go back to my notes, but I think the only difference is that I mashed for 90 minutes for the Saison and Blond. I don't see how that made enough of the difference, but maybe so?

The 90 minute mash shouldn't make enough of a difference, but BE-134 is disataticus positive, so perhaps the difference is the lower gravity on the saison and blond. I would be willing to bet that given enough time on the higher gravity styles, they would have eventually done the same.

If you want to stick with that strain, you could always stop fermentation by adding sulfites (campden, potassium metabisulfite), but I'm not a huge fan of that method in beer, especially if you're bottle conditioning. Honestly, for the lower gravity styles, you might explore a different strain with a 'similar' flavor profile, like WLP565. Might make the whole process easier!

 

[SRJHops]

Mixing yeast strains doesn't work like that. The most attenuative strain won't "stop short" just because either less attenuative strains are in the mix.

So I should have used the highest attenuating yeast to predict FG, right? The Brewer's Friend software did not do that. It averaged the yeast blends and predicted 80% attenuation.

 

[SRJHops]

The 90 minute mash shouldn't make enough of a difference, but BE-134 is disataticus positive, so perhaps the difference is the lower gravity on the saison and blond. I would be willing to bet that given enough time on the higher gravity styles, they would have eventually done the same.

If you want to stick with that strain, you could always stop fermentation by adding sulfites (campden, potassium metabisulfite), but I'm not a huge fan of that method in beer, especially if you're bottle conditioning. Honestly, for the lower gravity styles, you might explore a different strain with a 'similar' flavor profile, like WLP565. Might make the whole process easier!

You are correct that all the other beers had higher OGs. Other than the quad, I drank them all up. But I could test the quad over the next few months to see if the yeast is still chewing away. I will say that all the FGs were stable for three weeks before I bottled.

Are all Saison strains disataticus positive? It does look like WLP565 is less attenuative than Be-134.

 

[VikeMan]

Are all Saison strains disataticus positive? It does look like WLP565 is less attenuative than Be-134.

There are strains that people have used in "saisons" that are not STA1 strains, but every strain I know of that makes a saison that tastes like a saison is.

 

[SRJHops]

Thanks for all the replies -- I've learned a ton this morning.

Here's related question: As VikeMan and Barbarossa noted, even at 1.000 FG there are some residual sugars. Be-134 has an average attenuation of 90%. It seems to me that it's more like 100%, but can I get to 1.000 with 90% attenuation?

 

[VikeMan]

Here's related question: As VikeMan and Barbarossa noted, even at 1.000 FG there are some residual sugars. Be-134 has an average attenuation of 90%. It seems to me that it's more like 100%, but can I get to 1.000 with 90% attenuation?

Maybe not residual sugars, but residual dextrins. These normally "unfermentable" dextrins can be broken down and used to various extents by STA1 strains.

You cannot get to 1.000 with 90% Apparent Attenuation. By definition, 1.000 is 100% Apparent Attenuation.

Also, yeast strains don't always attenuate at a rate that's within the yeast vendor's published range.

 

[SRJHops]

Maybe not residual sugars, but residual dextrins. These normally "unfermentable" dextrins can be broken down and used to various extents by STA1 strains.

You cannot get to 1.000 with 90% Apparent Attenuation. By definition, 1.000 is 100% Apparent Attenuation.

Also, yeast strains don't always attenuate at a rate that's within the yeast vendor's published range.

Thanks. So, we are left with the fact that most Saison yeast strains ferment down to 100% apparent attenuation (if you let them, over time), but the manufacturer's for some reason don't list that? Correct?

 

[VikeMan]

Thanks. So, we are left with the fact that most Saison yeast strains ferment down to 100% apparent attenuation (if you let them, over time), but the manufacturer's for some reason don't list that? Correct?

I wouldn't say that every Saison strain will take a "typical" wort to 100% apparent attenuation. The Dupont strain(s), like Wyeast 3724, seems to be a little gentler, for example.

 

[SRJHops]

I wouldn't say that every Saison strain will take a "typical" wort to 100% apparent attenuation. The Dupont strain(s), like Wyeast 3724, seems to be a little gentler, for example.

Cool. I really appreciate your (and BrewChatter's and everyone's ) help!

Since it seems to work in my high OG Belgians -- and I want it for the Saison -- I think I'm still good to go with the Be-134. I just won't use it for a lower OG blond if I want it to have a little sweetness.

I of course can't wait to try the 1.000 blond that is conditioning right now. It will be high ABV, dry and not that bitter (IBU 19), with spice and fruit (hopefully some banana and bubblegum). So it's entirely possible that I will stick with the recipe. But it was important for me to figure out what was going on and learn from it -- thanks again!

 

[BrewChatter]

 

[cmac62]

Side question: Is Lactose broken down by the STA1 strains? Because I was thinking that adding some would help with OPs issue. Thanks

 

[bracconiere]

you didn't say what size batch, i don't think. but if i punch it into beersmith it gives me an options to check add after boil.

but i'm trying to figure out your recipe in reverse, and batch size so i can punch it into beersmith, to see what it tells me that sugar would do...


i stubbed out a 5 gallon batch, and a pound would drop the FG by 2 points...but 5lb's would drop it to 1.000

so if this was a 1 gallon batch it makes sense? and i guestimate a grain bill if you state your OG?

 

[SRJHops]

you didn't say what size batch, i don't think. but if i punch it into beersmith it gives me an options to check add after boil.

but i'm trying to figure out your recipe in reverse, and batch size so i can punch it into beersmith, to see what it tells me that sugar would do...


i stubbed out a 5 gallon batch, and a pound would drop the FG by 2 points...but 5lb's would drop it to 1.000

so if this was a 1 gallon batch it makes sense? and i guestimate a grain bill if you state your OG?

Here's the recipe. Thanks for your help. As you will see, the predicted FG was 1.013. I was trying to keep the ABV to under 7.5%.

https://www.brewersfriend.com/homebrew/recipe/view/1131988/blond
Love to see what Beersmith says. Also if I did anything wrong with the Brewer's Friend calculator...

 

[SRJHops]

Side question: Is Lactose broken down by the STA1 strains? Because I was thinking that adding some would help with OPs issue. Thanks

Interesting question.. I am guessing not? So I could throw in some lactose or erythritol and get the FG up.

Probably won't do that for this beer, though. Won't reduce the ABV and there's a pretty good chance the yeast and grain will give a perception of sweetness. I made a Saison the other month that was also 1.000, and it had a hint of sweetness. So I think FG is only one measure of the perceived sweetness....

 

[VikeMan]

Shot in the dark here... have you checked your hydrometer in plain water?

 

[bracconiere]

beersmith agrees...my eyes are peeled for an outcome of this though, because i have to spend $30 a year on gluco right now to get 1.000....

 

[bracconiere]

on a new to me note, do you have a refractometer along with the hydrometer? i'd be curious what they read side by side....

 

[SRJHops]

on a new to me note, do you have a refractometer along with the hydrometer? i'd be curious what they read side by side....

I have a Tilt in there now, and it tends to be pretty accurate on the FG, not as good at OG. So I take OG with a refractometer, hydrometer, and the Tilt. OF COURSE I get three different readings! I tend to trust the hydrometer when push comes to shove.

 

[SRJHops]

beersmith agrees...my eyes are peeled for an outcome of this though, because i have to spend $30 a year on gluco right now to get 1.000....

Beersmith agrees that it should have finished at 1.013?

I think the conclusion/answer is that the Saison yeast ate up the non-fermentable sugars. It does not explain why the recipe calculators are not calibrated for this, but perhaps there are just too many variables....

 

[bracconiere]

acording to beersmiths trick i just recently learned if you took a refrac reading it should be ~6.5 Brix then....

 

[SRJHops]

Shot in the dark here... have you checked your hydrometer in plain water?

Great suggestion. Just got a reading of 1.002, so it appears to be a bit off. Good to know. I'll keep that in mind when I take the FG when bottling in a few weeks.

 

[dmtaylor]

I've reached a point in my brewing knowledge where I'm confused about unfermentable/residual sugars...

For my last brew, a Belgian Blond, I mashed at 154 in order to try to create some residual/unfermentable sugars. The recipe software said I would hit 1.012 FG, but instead all the sugar fermented out and I hit 1.000. Not a huge problem to have -- my Blond became a Tripel! But I don't understand what happened to the unfermentable sugars?

The Belgian yeasts (I blended 3) were supposed to be moderately attenuative, but certainly not 100%.

Here are some factors that I think likely contributed to the 1.000, but I still don't understand what happened to the unfermentable sugars:

1. I tend to blend yeasts and it's very possible I overpitched. (I didn't use a pitching calculator.) Can overpitching alone cause 100% attenuation?

2. I mashed at 154, but for 90 minutes. The long mash likely created a more fermentable wort as the temp dropped a few degrees, but 100% fermentable?

3. I used a pound of table sugar to thin out the body and add ABV. (It was included in the recipe calculator.) I know sugar ferments out 100%, but again, what happened to the unfermentable sugars? Does sugar somehow accelerate fermentation so much that the yeast eats up the unfermentable sugar too?

Of course, I do know what to try next time, and I could do experiments: I could mash even higher, use less yeast, less sugar, and a shorter mash. But I want to understand what's going on, so I can better control my numbers. Thanks for any help you could provide.

I'm answering your questions without reading anybody else's responses yet.

1. Which yeasts? (Hopefully someone else already asked.) The specific strains matter a LOT. Some are probably diastaticus, hence your high attenuation. Pitch rate and overpitching does NOT matter AT ALL.

2. Your mash temperature of 154 F is not very hot. If you want low fermentability, try like 158 F. Or even 160 F. Mash TIME is the overriding factor anyway. If you had mashed for just 30 minutes instead of 90 minutes, huge difference in attenuation. Also, your 100% attenuation is specifically "apparent" attenuation, not real attenuation. In reality, there's still sugars left even at 1.000. If nearly all of the sugars actually fermented out, you would be left with a gravity closer to like 0.990. Yes, seriously.

3. The sugar definitely affected attenuation. There are still some unfermented sugars, as mentioned above in #2. Just not as much as you expected. Sugar doesn't boost the yeast or anything like that. They just see it and eat it all, up to their alcohol tolerance anyway, which in this case was apparently not reached for at least one of the three yeasts you used.

I think diastaticus was at play here. Diastaticus variant yeasts are well known for producing FG of 1.000-1.002. Belle Saison and Wyeast 3711 are the most famous of these. Yeast matters most.

Next time mash at around 156 F for just 30-40 minutes, and avoid diastaticus. You'll get a different result. But the diastaticus yeast is key. If you still have diastaticus in there, you'll still get about 1.002 no matter what the heck you do with mash time or temperature.

Now I'll read everybody else's answers, and add editorial comments as appropriate. Hope some of us are singing the same song already. Cheers.

 

[bracconiere]

Beersmith agrees that it should have finished at 1.013?

yes it did....or 1.012

 

[SRJHops]

I'm answering your questions without reading anybody else's responses yet.

1. Which yeasts? (Hopefully someone else already asked.) The specific strains matter a LOT. Some are probably diastaticus, hence your high attenuation. Pitch rate and overpitching does NOT matter AT ALL.

2. Your mash temperature of 154 F is not very hot. If you want low fermentability, try like 158 F. Or even 160 F. Mash TIME is the overriding factor anyway. If you had mashed for just 30 minutes instead of 90 minutes, huge difference in attenuation. Also, your 100% attenuation is specifically "apparent" attenuation, not real attenuation. In reality, there's still sugars left even at 1.000. If nearly all of the sugars actually fermented out, you would be left with a gravity closer to like 0.990. Yes, seriously.

3. The sugar definitely affected attenuation. There are still some unfermented sugars, as mentioned above in #2. Just not as much as you expected. Sugar doesn't boost the yeast or anything like that. They just see it and eat it all, up to their alcohol tolerance anyway, which in this case was apparently not reached for at least one of the three yeasts you used.

I think diastaticus was at play here. Diastaticus variant yeasts are well known for producing FG of 1.000-1.002. Belle Saison and Wyeast 3711 are the most famous of these. Yeast matters most.

Next time mash at around 156 F for just 30-40 minutes, and avoid diastaticus. You'll get a different result. But the diastaticus yeast is key. If you still have diastaticus in there, you'll still get about 1.002 no matter what the heck you do with mash time or temperature.

Now I'll read everybody else's answers, and add editorial comments as appropriate. Hope some of us are singing the same song already. Cheers.

No need to read the others - you are spot on! Actually glad you answered this way -- good to see it all put together. Thanks!

 

[SRJHops]

yes it did....or 1.012

I guess that means the recipe calculators aren't so good at diastaticus variant yeasts. (I'm not too proud to admit that I didn't even know that word before today.) Much appreciation to you all!

 

[dmtaylor]

Side question: Is Lactose broken down by the STA1 strains? Because I was thinking that adding some would help with OPs issue. Thanks

Nope, diastaticus yeasts cannot eat lactose. This is one option to increase FG if desired. About a half pound in 5 gallons can take the edge off a bit and add approximately 0.005.

 

[dmtaylor]

Here's the recipe. Thanks for your help. As you will see, the predicted FG was 1.013. I was trying to keep the ABV to under 7.5%.

https://www.brewersfriend.com/homebrew/recipe/view/1131988/blond
Love to see what Beersmith says. Also if I did anything wrong with the Brewer's Friend calculator...

Thanks for the recipe. All 3 of your yeasts are diastaticus. The "worst offender" could have been any of the 3, I'm not sure which one.

 

[dmtaylor]

I have a Tilt in there now, and it tends to be pretty accurate on the FG, not as good at OG. So I take OG with a refractometer, hydrometer, and the Tilt. OF COURSE I get three different readings! I tend to trust the hydrometer when push comes to shove.

Here's some stuff from me about the Tilt:

https://www.homebrewersassociation.org/forum/index.php?topic=32797.msg432694#msg432694
In particular:

" When yeast and hops are stuck to the Tilt, it will make the SG read lower than it really is. Don't be surprised when your FG ends up being 1.006 when you expected 1.012 or whatever. "

 

[SRJHops]

Here's some stuff from me about the Tilt:

https://www.homebrewersassociation.org/forum/index.php?topic=32797.msg432694#msg432694
In particular:

" When yeast and hops are stuck to the Tilt, it will make the SG read lower than it really is. Don't be surprised when your FG ends up being 1.006 when you expected 1.012 or whatever. "

Agreed. I do check with a hydrometer for the FINAL FG. I also got 1.000 on my last beer using the same 3 yeasts.

 

[SRJHops]

Thanks for the recipe. All 3 of your yeasts are diastaticus. The "worst offender" could have been any of the 3, I'm not sure which one.

What? Really? Sheesh. Are ALL Belgian yeasts diastaticus? I thought the offender was the Be-134 Saison yeast. The other two are just regular ol' Belgian yeasts...

 

[dmtaylor]

Agreed. I do check with a hydrometer for the FINAL FG. I also got 1.000 on my last beer.

If this has become a pattern where you are getting close to 1.000 for every beer... it might be a permanent "contamination" issue where diastaticus yeasts hide out in soft materials in your fermentation equipment, which can include hoses, stoppers, o-rings, buckets, etc. If this continues for many batches, it might be time to consider replacing all soft materials. I've had to do this a few times over the past 23 years when I started getting something off in my beers including super high attenuation.