Low OG lead to low FG?

[acarter5251]

I recently brewed a couple 4 gallon batches on my Grainfather that had the same issues:

Batch 1 Grain Bill: Key Lime Saison (from BYO magazine recipe)
5 lbs 9 oz Belgian Pilsner
3 lbs Maris Otter
8 oz Caramel 40L
5 oz Flaked Oats
14 oz Lactose

Mashed at 150F 60 min
Used Belle Saison yeast (attenuation=77-83%) @ 72F

Expected/Actual OG: 1.066/1.061
Expected/Actual FG: 1.018/1.011

Batch 2 Grain Bill: Strawberry Milkshake IPA (based off BYO magazine recipe)
8 lbs 4 oz 2 Row
2 lbs Flaked Oats
12 oz Lactose

Mashed at 150F 60 min
Used a 1:1 blend of Conan and Sach Bruxellensis Trois @ 68F

Expected/Actual OG: 1.080/1.072
Expected/Actual FG: 1.023/1.013

As you can see, I missed the OG on both of these batches by about 7-8 points. Could the low FG be a result of the yeast attenuating equally well but with a low OG?

On the other hand, the lactose should not be fermentable and would be expected to contribute about 6 or so points for the batch, which would make the FGs about 1.005 and 1.007 respectively for the two batches?

At this point I am just trying to rationalize why my FGs are so low when I used a healthy amount of lactose in both batches.

Thanks in advance!

 

[bucketnative]

How are you determining your target OG? A lot of factors go into the actual attenuation: pitch rate, oxygenation, mash temperature, etc...

I find that a lot of the calculators are off when it comes to predicting OG, especially with Belle Saison. That's my go to saison yeast, and it routinely finishes below 1.004, even when Brewer's Friend predicts 1.008 or above.

 

[acarter5251]

How are you determining your target OG? A lot of factors go into the actual attenuation: pitch rate, oxygenation, mash temperature, etc...

I find that a lot of the calculators are off when it comes to predicting OG, especially with Belle Saison. That's my go to saison yeast, and it routinely finishes below 1.004, even when Brewer's Friend predicts 1.008 or above.

Target OG and FG were from Beersmith predictions, which were in pretty good agreement with the BYO magazine recipes as well.

 

[Smellyglove]

You're using Belle Saison. This is a agressive Diastaticus yeast, it will eat most of the sugars and even starch (it coneverts startch to sugars) in the beer.

If you'd use a non diastaticus you'd see a more "normal" attenuation.

 

[bucketnative]

You're using Belle Saison. This is a agressive Diastaticus yeast, it will eat most of the sugars and even starch (it coneverts startch to sugars) in the beer.

Agreed with your post. In fact, I was wondering if the Belle Saison was actually done at 1.011?

 

[Smellyglove]

Agreed with your post. In fact, I was wondering if the Belle Saison was actually done at 1.011?

OP said that without lactose the FG would have been 1.005 and 1.007, even that seems high.

 

[acarter5251]

Agreed with your post. In fact, I was wondering if the Belle Saison was actually done at 1.011?

It could still be going. That's just where it is currently sitting

 

[Smellyglove]

It could still be going. That's just where it is currently sitting

Bingo.

 

[bucketnative]

It could still be going. That's just where it is currently sitting

OK, your use of "FG" implies "final gravity", which implies the point at which you packaged your beer. If it's not final, I would use SG, which refers to the more generic "specific gravity" term.

 

[acarter5251]

OK, your use of "FG" implies "final gravity", which implies the point at which you packaged your beer. If it's not final, I would use SG, which refers to the more generic "specific gravity" term.

Either way, the gravity hasn't budged since I last checked it a week ago and krausen had dropped completely a week ago, so it's looking pretty final to me

 

[kh54s10]

Final gravity in any calculator is a prediction. I don't pay much attention to it. In fact in looking at my recipes, the few that I remembered to note the FG on, none were exact. Most varied 2-4 points up or down.

 

[El Nino]

Usually lower mash temperatures = lower FG, but if it was at 150 and didn't drift downward too much, it shouldn't be the case.

However, in my last 2 brews, I've gotten a lower than expected FG doing the same recipe. Didn't seem to affect the taste none, and more bang for my buck, I'm not complaining haha.

The first time my FG was 1.006 (mashing at 150), and the 2nd time was 1.010 (mashing at 152). Try upping your mash temp to 152 if you want a slightly higher FG.