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Is it bad to cool mash runnings before the boil?

Is allowing your mash runnings to cool to room temp over 18 hours before starting the boil a bad idea?
I brew extremely high gravity (1.120 - 1.140 OG) lagers. I mash 30# of grain to collect 15 gallons of runnings which I then boil down to 6 gallons (twin brew kettle 2.5 hour boil). Getting that and the associated cleanup done (during and after) can make for a very long brew day (10+ hours). The last couple of batches, I split the process over two days by mashing and collecting my runnings on the first day (usually done around noon), then letting the full brew kettles sit over night and starting the boil early (5AM) the next morning. My batches spend 2-3 months in primary before a 10 week diacetyl/secondary/lagering regime, so the lag time between starting a batch and sampling the result can be almost half a year. I’m ready to start another couple of batches, but being a natural worrier, I’m worried that maybe letting the runnings sit over night might introduce undesired results. Before collecting any runnings, I mash out to 190F+ and my grain bed remains above 180F for the entire lauter/sparge. When I turn on the kettles for the boil the next morning, the runnings have cooled to 70F (I live in Alaska). Any other comments regarding my process are greatly appreciated.

I’d say as long as you mash out above 170F you’ll be effectively pasteurize the wort so it won’t sour overnight. Its wasteful of heat but if thats not a problem for you then it should be fine. YOu’re 190F mashout is pretty extreme, you do that for any particular reason? I know if you have your pH right it shouldn’t extract tannins but at the least its just that much more heat you are wasting.

I do this when I’m strapped for time. I mash one evening, store the wort in a fermenter overnight and then boil the next morning. I’ve seen no ill effects, it just takes longer to boil because I’m starting the wort at room temp instead of the 170 degrees or so it would be coming out of the mash.

My two-day protocol includes the boil, then I turn off the heat, put on the lid and run off in the morning. Your basic no-chill method, minus running it hot into a container. Of course this only works for malty beers with little or no late hop additions.

I always thought you wanted to keep the sparge below 170*? Maybe you are on to something.

I would be inclined to bring the wort to a boil for a couple minutes. Then put a lid on the pot and turn the flame off. Doing a complete boil the next day.

Or do the complete boil and ‘no chill’ it overnight.

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