I'm getting increasingly frustrated about this attenuation issue. I just took a final gravity reading for my recent BoPils and it's 1.007 (I was estimating 1.014). Here was my recipe/process:
5.33 gallon batch
6.25# Weyermann floor-malted bohemian pilsner
2.25# Best Malz Pilsner
.50# Cara Pils
.30# Acid malt
Infuse w/18 qts H2O ==> Beta rest @ 145 for 25 minutes
Pull thick 8.5-qt decoction; raise to 158 and hold for 15 minutes
Boil thick decoction for 30 minutes
Remix thick decoction and raise main mash to Alpha rest @ 158 for 40 minutes
Pull thin 6.5-qt decoction and raise to boiling
Remix thin decoction and raise main mash to mashout temp @ 168 for 10 minutes
Mash pH was 5.4 throughout.
I pitched only the slurry from a 1.5L stirplate starter made from 2 smackpacks of Wyeast 2001. I fermented between 50-52 degrees for 14 days; the gravity was 1.012-1.013 on the 14th day of fermentation. I removed the fermenter from the cooling chamber and let it sit at 65 degrees for a 48-hour diacetyl rest. I then placed the fermenter back in the cooling chamber and gradually cooled the beer 5 degrees per day until I reached lagering temp.
Here are some nagging thoughts about my decoction procedure:
I mash in a 52-qt rectangular cooler, which means I can't directly heat my mash. This means that after I pull my first decoction, the main mash temp will stay around the low 140s until I add back the decoction. This can take up to an hour, depending on how long I boil the decoction. Will leaving the main mash at beta temps for that long basically set the fermentability of my wort? In other words, even if I raise the main mash to alpha temps after adding back the decoction, will the alpha rest actually make the wort less fermentable? Or am I stuck with a highly fermentable wort that sat at beta temps for a prolonged period of time? If my wort profile is basically set by the time I add back the thick decoction, it makes sense that my beers would be more attenuated (since the alpha rest isn't really doing much). As such, I might be better off just trying to hit my steps with infusions, since I can manipulate the rest times better that way given my setup.
Any thoughts/suggestions are much appreciated.