Posted 06 January 2012 - 06:08 AM
I almost never mashout, either. If you are sparging with 170°F water, the gradual temperature rise of the grain bed and the wort probably go through the equivalent of a short alpha rest, I'd think.On my system, running the math with a head cold, 10-20% additional conversion on a 1048 beer is the difference between 88% or 80%-72% efficiency. That would mean that at least 8-16% of the sugar would have been converted at an alpha rest. I think that means that the sugar from the alpha rest of that starch would have to be ~40-60% unfermentable to bump the FG by ~2 points, I think. That seems like it would be an easily noticeable change, if it was actually that unfermentable, but less might be enough to come across as a satisfyingly subtle increase in body and you would need less if you started the alpha rest earlier.Kai Troester did a mash temperature experiment on Pilsner Malt, followed by a fast ferment test for the upper limit of fementability from that wort. He measured a maximum fermentability of ~87-90% at 145 & 151°F and 60% at 167°F. Too bad he didn't test 148°F. I can't find if this is apparent or real attenuation, at the moment. (By the way, he found that attenuation decreased by ~4% for every 1°C, or ~2% for 1°F, increase in mash temperature above 151°F, in a very linear fashion.)That seems like a 40-60% unfermentable wort at 158-162°F might be a stretch, if you are depending on all the additional unfermentablity coming from just that bump in conversion, not some conversion that would have been completed at the lower mash temperature finishing at the higher temperature.Frankly, I just use this technique because it was the first one that gave me the results I was looking for, which was a dry tasting beer that wasn't lacking in body. When I started just raising the mash temperature in a single infusiion, my beer seemed to be getting a more cloying sweetness. When I tried a beta-alpha step mash, I got a dry tasting beer that had a nice body. There are so many variables in this process, and I've had other brewer's beers that were mashed warm that weren't sweet, that I think there are more than one ways to get the same result. This was just the first one I stumbled upon that worked in my brewery.