Overnight Mash and Final Gravity

Question here that I hope makes sense....

I'm wondering if an overnight mash where temps eventually drop into the low 140s might cause the final gravity to also be quite low.

I did my first ever overnight mash on a wheat beer (also my first wheat) and today transferred it over to the secondary. Took a gravity reading and was rather surprised to find it at 1.001. This got me thinking that maybe as the mash drops through the temps overnight that more enzymes are converting the starches into highly fermentable sugars instead of the longer chains that lead to a "thicker" beer. I started the mash at 154 hoping to get a little fuller mouthfeel and honestly hadn't considered the effect that the overnight temp drop might have had on the enzymes/starches. Not a big deal, mind you, as I'm sure I'll still enjoy the brew, but I'm just wondering if anyone has any experience with this. And if this is, indeed, the case, perhaps doing overnight mashes on beers that should have a "fuller" mouthfeel might not be a good idea.

Any ideas? thoughts? pointers?

If you want a "thicker" beer then you want to do a relatively quick mash. Mash at your desired temperature, like 154, until it passes an iodine test. Then mash out. Mashing out means you raise the temperature to around 165-70, which denatures the enzymes. At that point the enzymes will not break down more of the unfermentable sugars, leaving them in the brew to give the mouth feel. Do an overnight mash and those enzymes will nibble at those unfermentable sugars all night long, resulting in a thin beer with little or no mouth feel.

Assuming you have a well insulated container (the one time I tried it I awoke to a soured mess), an overnight mash would be ideal for something like a light pilsner.

Another thing to think about is that the lower the final gravity is, the less unfermentable sugars there will be to balance out the hops. So you'll get more perceived bitterness from them.

Last Saturday I brewed a Saison in a homebrewing competition at a local craft brewery.  We had this exact same conversation.  I mashed at 147 F.  I lost temperature during a 90 minute mash down to 142 F at the 45 minute mark.  I decided to decoct part of my mash and bring the temperature back up to 147 F.  Because it was a Saison, it probably wouldn't have hurt it to be more fermentable, but I didn't want to lose any mouthfeel that I would get at 147 F, compared to the mouthfeel that I might lose by letting it sit at 142 F for the last 45 minutes of the mash.

It probably wouldn't make much difference on my beer, because it's a Saison and it's supposed to finish very dry.  However, as the mash temperature drops, you do break up a lot of the longer chains into simple short chained sugars and you get a really fermentable wort.  I'm putting a flavored black tea and some hibiscus in the secondary of this one.  Because the teas, dried fruits and flowers are going to add sweetness and some tartness, I didn't want the brew to be too thin.

My starting gravity was 1.060.  I'm going to be checking the gravity tomorrow night when I add the tea and flowers.  I'm expecting it to be at around 1.004.

The winner will have their recipe brewed on the breweries 15 bbl system.

Thanks for the feedback, guys. And good luck, Scott, with the competition. Let me know how your beer does.

Had another thought. If I were to lose, say, 15F in temp in an overnight mash (roughly 8 hours), would it be feasible to start the mash around 165 and let it drop from there? Would that fix the problem of a too-fermentable wort?

would it be feasible to start the mash around 165 and let it drop from there?

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Probably not. I would think that would denature the enzymes, so when the temperature dropped into their active range, no conversion would occur.

Maine Homebrewer said:

would it be feasible to start the mash around 165 and let it drop from there?

Click to expand...

Probably not. I would think that would denature the enzymes, so when the temperature dropped into their active range, no conversion would occur.

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Right. Stupid question.

I've got one more example that could point that way too.  My previous batch was a black IPA, mashed overnight, and came in at about 1.003.  Otherwise the brew day was normal (BG, OG, volumes, etc).  Ended up sooo tasty.