I brewed two 3.5 gal BIAB batches of stout with the same grain bill, hops bill, and yeast (11.5 gr of rehydrated S-04). The only significant differences were that batch #1 was mashed at 160°F (OG = 1.050) and was fermented at 63°F, while batch #2 was mashed at 156°F (OG = 1.055) and fermented at 66°F. Both beers tasted great, but batch #2 had 30% more alcohol than batch #1 (4.6% vs 3.5%).
Both fermentations were for four weeks and both were roused and finished at about 70°F, so I would think the fermentations were complete. And all gravities were meticulously measured with a calibrated hydrometer. Given that the post-mash gravity and the OG of batch #2 were significantly higher than batch #1, that leaves the mash temperature as the main culprit in explaining the difference in ABV.
I expected that mashing at a higher temperature would produce more unfermentable sugars, but did not expect that only 4°F would make that big of a difference in ABV. Is the ABV that sensitive to mashing temperature?
TomVA
Both fermentations were for four weeks and both were roused and finished at about 70°F, so I would think the fermentations were complete. And all gravities were meticulously measured with a calibrated hydrometer. Given that the post-mash gravity and the OG of batch #2 were significantly higher than batch #1, that leaves the mash temperature as the main culprit in explaining the difference in ABV.
I expected that mashing at a higher temperature would produce more unfermentable sugars, but did not expect that only 4°F would make that big of a difference in ABV. Is the ABV that sensitive to mashing temperature?
TomVA