Low Final Gravity

[Crosley]

So the last 3 batches have finished quite a bit lower than expected and lower than all previous batches. This was around the 5th generation of this yeast so I thought it might be yeast related, so I tossed that strain and order fresh. I just brewed again and the same thing is happening.

Here's a little about this batch.
IPA
90lbs of grain / barrel mashed at 149-150
60 minute boil OG of 1.075
4LPM of o2 for 30 minutes
BSI 8bbl pitch for 6 barrels
Fermented at 69-70

I'm now on day 6 and it's dropped down to 1.014 (expected fg of 1.021)

Does anyone have any information of tips they might be able to pass along.
Thanks

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[Rooh]

What yeast strain is this? If it is related to the chico strain, that is not a low final gravity. That mash temp is pretty low, you should expect relatively high attenuation.

Rich DeLano
rich@thebrewinglair.com

[Crosley]

It's BSI- 1. Their American ale strain similar to 001

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[andrew_FSBC]

Have you added something unfermentable to your wort that would lead you to believe you should have that high of a final gravity? 1.014 is still a bit high for that strain at that mash temp and a very healthy pitch of yeast.

[BemidjiBrewing]

I'm on board with Rich and Andrew on this one - that seems right in the range for a Chico strain with that mash temp. What does the grist look like for this beer? Is it also low on caramel/crystal/dextrin malts? If this is a pretty pale IPA with a low percentage of specialty malts (or any unfermentables) I wouldn't be surprised if it finished in the 1.011 to 1.014 range with that starting gravity and mash temp.

Does this beer and its balance rely upon a higher finishing gravity? If so I would consider a higher (and maybe faster) mash rest and/or choosing a less attenuative yeast strain.

Also, there are a lot of variables in adding O2 to cooled wort but 30 minutes at 4LPM for 6bbl seems like a LOT of oxygen. But that's just my opinion on that topic...

Cheers,
Tom

[feinbera]

Maybe the right question to ask is, was there anything different about your recent batches versus the previous batches that finished higher? Any explicit changes to mash and fermentation temps and procedures? Adding that oxygenation step (or other steps)? Just getting your equipment and processes more dailed in so you hit your numbers on the head where you might have been mashing or fermenting a couple degrees off before?

[andrew_FSBC]

Maybe the right question to ask is, was there anything different about your recent batches versus the previous batches that finished higher? Any explicit changes to mash and fermentation temps and procedures? Adding that oxygenation step (or other steps)? Just getting your equipment and processes more dailed in so you hit your numbers on the head where you might have been mashing or fermenting a couple degrees off before?

Also this.

I was going to ask if you have calibrated whatever you are checking mash temp with.

[Junkyard]

If the recipe is the same +2 for calibrating and cross referencing your mash temp with multiple thermometers at multiple points (top of mash, mid of mash, wort grant temp possibly)

[organicbrewer]

I'll add, are you preheating your mash tun? At least where I live the brewhouse is 40f cooler than it was over the summer. That could lower your effective mash temp.

[Crosley]

Maybe the right question to ask is, was there anything different about your recent batches versus the previous batches that finished higher? Any explicit changes to mash and fermentation temps and procedures? Adding that oxygenation step (or other steps)? Just getting your equipment and processes more dailed in so you hit your numbers on the head where you might have been mashing or fermenting a couple degrees off before?

That's kind of what spurred this thread is that I've brewed this recipe over 50 times and my FG numbers are normally around 1.019-1.021. Same with the other batches that did the same thing, they were spot on before and then just all of a sudden they were finishing low. That's why I tossed the yeast I was using and start from scratch.

[Crosley]

If the recipe is the same +2 for calibrating and cross referencing your mash temp with multiple thermometers at multiple points (top of mash, mid of mash, wort grant temp possibly)

I came in this am to brew a second batch of something and I pulled the temp probe and added some heat gel and it was still reading the same. I also manually checked the mash temp and it was spot on with the probe.

[Crosley]

I'll add, are you preheating your mash tun? At least where I live the brewhouse is 40f cooler than it was over the summer. That could lower your effective mash temp.

I try to preheat the mash tun just with a god hot water rinse. I'm in a cold area also and I actually have just figured out my water temp based on summer versus winter. My water temp needs to be roughly 2 degrees warmer in the winter months.

[WappingBeer]

Different base malt?

FG 1.019 to 1.021 seems high for WLP001. Anyway, just wondering if the supplier or base malt has changed that could cause higher attenuation. Also - has mill gap setting changed?

[Crosley]

Thanks everyone for all of the responses. Since nothing has changes on the process side it looks like it's time to go back to the drawing board and tweak the recipe. You guys are right, with that yeast I should be finishing lower than 1.021. I'll make some changes and then report back.

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[Crosley]

OK last question. I was in checking gravities this morning and checked this IPA in question, 1.010. The more research I've done and your information this seems right in line with this yeast. This is what got me thinking in the beginning, on these beers when they've finished low they seem to rage for 2 days and then start to die off. This beer is bubbling ever so slightly still and only dropping .001 per day for 4 days now. This batch is 8 days old and still in fermentation.
This is odd to me. Anyone have any information that may help.

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