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Doing the mash a few days before brewing

I have a parshall mash clone that I am getting to try. Is there anything wrong with doing the 45 min mash one night and store it in the fridge and doing my 60 boil later in the week.

Not optimal but it’s been done before, I’m sure. Boiling your wort later will reduce the risk of any problems encountered from the delay. Practice good technique and it should be fine.

After having partial mashed for awhile before going all grain, I really prefer the setup I have for all grain. If I get back to doing smaller batches indoors (either partial mash or all grain), I’ll approach it the same way as I do now. I would make a mini-mash tun to use indoors. Heat the strike water, put it in the cooler, stir in the grain and go do something else for awhile. I’ve done mashes for my AG where once it’s in the cooler, I take my dog for a short (45 minute or so) walk. Then my German Shepherd is content to lay and watch me finish brewing.

Is it possible he could end up with a sour?


@hd4mark is right. You will have to boil it to kill any bacteria that made its way into the kettle. Grain is full of bacteria, especially lactobacillius, which will sour it. Chilling will help with bacteria spoilage but you will have to chill it very fast.

I think I would just take the additional hour and make the beer rather than risk it.

I agree that you are running the risk of cultivating bacteria. But, if you don’t have the time to do a full 60 minute boil, you can pasteurize it by raising the temp above 170 for 10 minutes, and it will keep in the fridge better.

Right…mash out at completion of the mash at 170* for 10 minutes should get rid of Lactobacillus. Spores, well, even boiling wort doesn’t get rid of all spores.

I’ve done overnight mash. I would not wait a few days to boil. If I was short on time I would do an extract batch

Thanks for your help. I will not ask for trouble and just go for the longer brew day. I just thought that the one hour boil would kill anything that may have been pick up

The boil will kill lacto but the damage may already be done. There’s a process called kettle souring that’s specifically for this.

Although you could boil it for a short period and then chill to pitching temps and then pop it into the fridge, you would have to maintain a very clean process. Why risk it to save an hour or so?

Other option - look into no-chill brewing. Basically put the boiling wort into a food-grade plastic container, squeeze out all the air, and leave it at room temperature. Only one caveat, and it’s really important…


Boiling does not kill botulism spores, and their incubation period is 4 days. This is serious stuff, people die from botulism. But if you only need a couple days, you can do this safely.


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