Mash Time

[gbrewer]

I've been brewing all grain for some time now but started to question some of my processes. Not a question of something not working, rather a question of how to make them better.

Today I was brewing a Kolsch. I have a fairly deluxe brew sculpture which uses a RIMS tube along with propane burners for strike water and boil kettle. I recirculate during the entire mash since I am using a RIMS tube.

For Christmas, I received a refractometer. I was playing with the refractometer today during the mash. At around 30 minutes, I took a sample reading of the mash and discovered it to be a 1.055. I understand that this is not my pre-boil gravity since it will be thinned out prior to going into the boil kettle. (Mash out) I was curious if I had reached conversion so I decided to do the starch / Iodine test. The iodine turned the appropriate color indicating conversion had occurred. I tested my gravity again approximately 10 minutes later and noticed it to be the same at 1.055. I typically do a by-the-book one hour mash.

It appears that I reached conversion at around 30 minutes. Was there anything gained by mashing for an additional 30 minutes?
What might have happened if I started the mash out at 30 minutes?

[dmtaylor]

The whole reason for extending the mash beyond about the first 15-20 minutes is for the purpose of fermentability, not conversion. You've got all your sugar in there after just a few minutes of the mash, but they are complex sugars that won't ferment out as well as you want. The enzymes in the mash continue to break down the complex molecules into more digestible ones after starch conversion is essentially completed. You could boil and ferment your 1.055 beer mashed for only 15-30 minutes, but your final gravity might end up being like 1.025 -- that kind of sucks. So you need to mash for 40-60 minutes to ensure your final gravity is more like 1.012-1.015 like you'd expect. I have run a lot of experimentation on this and I have found that 30 minutes was sometimes good enough for proper attenuation (about a 50/50 split of good vs. poor attenuation), 35 minutes was better, and 40 minutes is good enough for 90% of beer styles. So now I always mash for 40-45 minutes, and I've never looked back since.