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The 5 minute mash

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.


As you mentioned, attenuation may suffer.

Just because the starch converts to sugar doesn’t mean those long chain sugars have been chopped up into highly fermentable short chain sugars.

An interesting experiment would be to do a mash at say 5 minute intervals, measure and graph the fermentability of each.

I love these kinds of experiments. I have run my own, although the shortest mashes I have done were 15-20 minutes. I found that attenuation will indeed suffer. Meanwhile your efficiency is probably almost as good as if you had done a 60 minute mash. So efficiency is not the issue, but rather attenuation.

I like your idea of the reverse step mash. This is something I have always been very interested in but have not yet experimented with myself.

Please share your results! Thanks!!


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