Attenuation issues

[St3in]

I'm curious if anyone is running into attenuation issues using Weyermann malts lately. I have seen that my Pils (66% Weyermann) is routinely failing to attenuate and fermentation is halting at ~3.2 plato. I have been producing this product for roughly 8 years, and it has always finished out ~2.2 plato. I do not believe this is a process issue, all other brands are attenuating as expected. To be safe, I went ahead and calibrated all temperature probes on the brewhouse. They were within 1 degree. Thought perhaps the lager yeast was getting sluggish so I brought in a new pitch. First brew, I reduced the mash temp to force over-attenuation - Pils failed to attenuate to expected target, and stopped at ~3.2 plato. Interesting.

To add another degree of complexity, I have 2 lagers both with similar OG's, same grist/H20 ratio, same mill gap, and same mash residence times. Lager (100% cargill) finishes as expected and Pils fails to attenuate, halting at ~3.2 plato.

So, I seem to have an issue with 1 Lager where the only difference is the grain bill. I'm fairly certain we can say it is not a problem with yeast, process, O2. Ideas? Am I missing something?

Cheers

[jebzter]

What does the COA about the malt say? I would suspect you will see some differences between the two bases. This would be where I would check for the problem, might need to adjust your mash regime for some differences in the malt, beyond just temperature.

[Brewtech11]

Attenuation blues

I'm curious if anyone is running into attenuation issues using Weyermann malts lately. I have seen that my Pils (66% Weyermann) is routinely failing to attenuate and fermentation is halting at ~3.2 plato. I have been producing this product for roughly 8 years, and it has always finished out ~2.2 plato. I do not believe this is a process issue, all other brands are attenuating as expected. To be safe, I went ahead and calibrated all temperature probes on the brewhouse. They were within 1 degree. Thought perhaps the lager yeast was getting sluggish so I brought in a new pitch. First brew, I reduced the mash temp to force over-attenuation - Pils failed to attenuate to expected target, and stopped at ~3.2 plato. Interesting.

To add another degree of complexity, I have 2 lagers both with similar OG's, same grist/H20 ratio, same mill gap, and same mash residence times. Lager (100% cargill) finishes as expected and Pils fails to attenuate, halting at ~3.2 plato.

So, I seem to have an issue with 1 Lager where the only difference is the grain bill. I'm fairly certain we can say it is not a problem with yeast, process, O2. Ideas? Am I missing something?

Cheers

One of two things is happening - either your carbohydrate profile in the wort has changed, or your yeast is not performing as it once was. Chances are it's the latter. In order to confirm, next time you make the beer take some oxygenated wort and put it in a 1L flask. Over pitch it with your typical yeast and put it on a stir plate in your lab or other warmish place. It should completely ferment out in a day and a half if constantly stirred. Check the finished gravity on this sample (heretofore referred to as the QF or quick ferment sample). If it is 3.2, which I doubt, it is the carbohydrate profile and you have to look at further adjustments to your mashing regime. If the QF finishes where the beer used to it is your yeast pooping out at the end of fermentation most likely due to premature yeast flocculation (PYF). PYF can most definitely be caused by malt. The mechanisms are still not fully understood but they are thought to be process related rather than barley related. Likely culprits are anaerobic steeping or excessive osmotic pressure during same. If you google premature yeast flocculation you will find out more information than you want to know. If this is in fact the cause you will have to take it up with the maltster to see if they routinely check for PYF. It is a fairly simple test done in an Imhoff cone with some yeast at the malthouse. If they do not run these tests and if another lot number doesn't fix the issue, you may be forced to look for another pils malt, or get used to sweeter beer. I have also seen attenuation issues where the malt had insufficient FAN levels, but these were only in very high gravity beers with very high degrees of attenuation. In theory all malt should have enough FAN if you are making non adjunct beers, but anecdotally this seems not to be the case when you are expecting too much from the yeast. Again, this doesn't sound like your situation at all.

[grnis]

Free Amino Nitrogen would be my guess.
The last harvest in northern Europe has had lower levels of FAN. The previous brewery I worked at have had problems with attenuation this year, so when I went back to work there a couple of weeks during vacation time this summer I added a protein rest and this seems to have fixed the issue.