Low attenuation/high FG on all brews

[mjphoto]

Hi Team,

I have been having some issues on the last 5 brews I have done (since getting a new system) with low apparent attenuation of the yeast or high final gravity. All brews seem to be consistently coming out 5-6 points above the estimated FG.

Set Up:

3 Vessel electric HERMS 5gal (batch size) system. Mash efficiency 78% Brewhouse efficiency 66%.
SS Brewtech Brewbucket fermenters inside a temp controlled fridge with an accuracy of +-0.1 deg Celsius.
Yeast Starter temperature controlled chamber with a stir plate.
Beersmith 3 for all recipes.

After stirring my grains in to the strike water (calculated temps in Beersmith 3) the mash temp stabilizes within a couple of mins and stays constant for the entire mash. The mash temp at the top of the Mash tun is approximately 1 deg different to the bottom and remains very consistent.

My water has been tested and I treat it accordingly for each brew. Mash PH is always between 5.2 and 5.3.

I have tried different ways of pitching yeasts and different yeasts - dry yeast rehydrate, dry yeast not rehydrated, liquid yeast large starter, decanted starter and liquid yeast straight from the pouch. Yeasts have been Safale US05, Mangrove Jacks M44, WLP001, WLP090. Yeast is always pitched in to well aerated wort.

I check the gravity with a hydrometer and then recheck with a different hydrometer. For FG lately I have been checking straight out of the fermenter at fermentation temps then checking again once the beer is cooled and fined (with gelatin) then warmed back up to 20deg (hydrometer calibration temperature).

My previous system was a Robobrew and I never didn't hit my estimated FG over 15 batches, the only thing that has changed in the process is going to a 3 Vessel system.

Here is a link to some of the sample recipes I have done - http://beersmithrecipes.com/listrecipes/143366/lasersnake

I just pulled two beers out of the fermenters and here are the numbers for them;

6Foot5 IPA - 23l Batch

6.35kg Pale Malt (93%)
0.16kg Cara-Pils (2.3%)
0.16kg Medium Crystal (2.3%)
0.16kg Vienna (2.3%)

3 Packs of Mangrove Jacks M44 rehydrated. Fermented at 19.5deg for 7 days then slow rise to 21 for 5 days.

Estimated OG = 1.062
Actual OG = 1.061

Estimated FG = 1.011
Actual FG = 1.016


And the other batch;

S Bomb IPA - 23l Batch

6.60kg Pale Malt (89.6%)
0.77kg Medium Crystal (10.4%)

2l Starter with WLP001. Fermented at 19.5deg for 7 days then slow rise to 21 for 5 days.

Estimated OG = 1.066
Actual OG = 1.065

Estimated FG = 1.013
Actual FG = 1.019

My yeast attenuation for these is around 70% which is lower than the low side of both yeasts used.

I think it is very strange that all batches are consistently 5-6 points above estimated FG. If anyone has any ideas I would be really grateful.

 

[jcav]

You may have a hydrometer calibration issue. I would put distilled water in your hydrometer testing tube and put it in the fridge until you hit 60 degrees (or whatever your hydrometer's calibration temp is) and check it with a thermometer. Then test your hydrometer and see if it reads zero at your calibration temp. If it's high that is the number you need to subtract from your readings. So let's say it reads four points high, you need to subtract four points from every reading with that hydrometer. Then put your hydrometer into your wort/beer and check the temp and enter the temp and the reading into a hydrometer reference chart (or software tool like BeerSmith) to get the real reading at the temp you are measuring. I bet your hydrometer is testing four to six points high, so you really are getting better attenuation then you think. Just a hunch though as I have seen this before. So I would calibrate my hydrometer first and see if this is the problem, and eliminate that first. Just my two cents.....

John

 

[V-Fib]

The 2 things that come to mind are mash temp and the stress you're putting on the yeast. Checking mash temp should be a simple fix. Try to think back to how you used to aerate. Are you doing the same exact thing now? Maybe try doing what ever you do a little longer or right before you pitch the yeast.

 

[mjphoto]

You may have a hydrometer calibration issue.

I am doing a calibration test right now... would be strange that both hydrometers are out though!

The 2 things that come to mind are mash temp and the stress you're putting on the yeast. Checking mash temp should be a simple fix. Try to think back to how you used to aerate. Are you doing the same exact thing now? Maybe try doing what ever you do a little longer or right before you pitch the yeast.

Yeah the mash temp would need to be significantly off to effect the attenuation this much though... playing around in beersmith I would need to be off by 4-5degrees Celsius which is definitely isn't, I have tested the temp with three thermometers and they are all very similar (within their own range of precision/accuracy).

As for aeration I basically use the shake method and shake for a while! I used an aquarium pump for one batch and it did not do the job very well at all (didn't start fermenting for 3 days as opposed to the 12 hours it usually takes... may have been another issue but the shake has always worked) so went back to the shake method.

 

[couchsending]

You don’t need to aerate with dry yeast so that’s not the problem.

Something must not be calibrated??

 

[Mer-man]

Have you verified your thermometer?

 

[stevehaun]

I apologize if I missed it, but what was your mash temp?