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Getting Lower Attenuation

So my last several batches have finished way too low for my liking and I can’t figure out why. These are all grain-only (no sugar) batches, usually around 1.060-1.070, and many having been finishing around 1.010. This is with a mash temp of 154*. I’ve double checked the hydrometer (which if anything reads a little high, not low), and double checked my thermapen in an ice bath and at boiling temp, so i don’t think its a measurement issue, and am kind of at a loss and how I keep getting so much attenuation, even with high mash temps.

This is happening on a wide ranges of brews (kolschs, reds, ambers) and with a variety of yeasts as well (05, WY 2565, Wy 1007).

The only thing I can think of is that i generally mash overnight so I can get up early and be done by 11, which helps keep the wife happy. Usually experience a temp drop overnight from 154 to the mid 140’s. However, from everything I’ve read, the fermentability of the wort is ‘set’ within the first hour or so as all the starch has been converted, so the extended time in the mash sitting in the 140’s shouldn’t really affect anything.

Anyone got any bright ideas? Start mashing at 158? Only use british yeast and add lactose to every batch?

I don’t know if I have any ‘bright’ ideas, but I have a couple thoughts.

  1. Are you sure your initial gravity readings are taken on fully stirred wort? Depending on your sampling technique you could possible be getting artificially high readings. For example, if you sample from the bottom of your kettle without stirring your wort first, I would expect your gravity readings to be artificially high as your first runnings which end up in the bottom of the kettle will be higher gravity than your later runnings at the top of the kettle.

  2. Can you brew a batch without the overnight mash to see if you get a different results? I don’t know a lot about the process in which enzymes become denatured, but I don’t think 100% of the enzymes are always completely denatured after 60 minutes, so you could still have some enzyme activity going on over night that creates a highly fermentable wort.

Its definately a direct result of the long overnight mashing,
You let the enzymes work on the carbohydrates for that long,
You end up with a wort that’s rich with broken down simple sugars.
At that point, any yeast is going to attenuate off their “chart”.
Do you feel that the high attenuation is negatively affecting your brews (flavor/mouthfeel) ? Try a standard 60 minute mash again, if you don’t enjoy the finished product any more/less, than don’t stray from your current S.O.P.

Yep, definitely caused by the extended period in the 140s - the enyzmes keep munching away, breaking down the longer chains that were formed in the earlier, warmer mash. I use an overnight mash any time I’m making a big Belgian just for this reason.

One time I let my mash go 95 minutes instead of my normal 45, I ended up with a 5 point lower than usual F G.

A brown I just kegged that went through a regular mash finished at 1.016 from 1.062 using wy 1335 and a 152 mash, so I think u may all be onto something…bummer, I really liked the convenience of the overnight mash. Now how to break it to the wife…

Shouldn’t you be able to stop the enzymes with a mash-out? Any reason you can’t take it up to 170 before you walk away?

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