I ran an experiment Sunday with a one gallon test brew. 2.5 gallons is my standard brew. My objective was to cut brew time to a minimum. The program was as follows using BIAB:
1: Dough in at 130F (hot tap water), with the pot on high heat
2: Reduce temp to a temp rise of 1 deg per minute at 145F and start testing for conversion with refractometer and iodine test
3: If the temp hit 155 before full conversion, shut the heat off and allow the temp to fall and hold
4: At full conversion, crank the heat up and head for a boil, lifting the bag and squeezing at 165.
5: Proceed as usual.
- Conversion started at around 148-149. I stirred the whole time. The effect was visually dramatic. The cloudy wort cleared right up, and gravity climbed rapidly and leveled off, and the iodine test went negative after about 3 minutes, and the refractometer reading leveled out. At 5 minutes, I deemed the mash done. My gravity was well above my expected gravity I consider it a 5 minute mash, though conversion happened so rapidly that it was actually less… I just wasn’t a believer.
The test brew is now fermenting, and I eagerly await the results. I’ve read that attenuation will suffer.
I’ve played with the idea of a “reverse step mash” in the past due to the fact that the breakage into long chains sets things up to break down into short chains which happens at a lower temp. On my agenda now is to do a 5 minute mash, add some cold water to drop the temp, and do a rest down around 145-148 for an additional 10 minutes, then turn the heat on and run up to mashout temp.