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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Mashed temp and FG
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Old 04-22-2013, 06:30 PM   #1
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Default Mashed temp and FG

Reading a bunch of threads on here, as well as looking back at some of the books I've got ( Palmer, Papazian ), I think I know the answer to my question, but looking for some additional input.

Last brew I made was an IPA. It's my 4th All Grain brew, with several extract and partial mash brews before that.

I've been working to get my consistency and efficiency better. I did much better this batch, hitting 1.062 (65%) of an optimal 1.068 (70%) OG. ( Measured with refractometer )

My error comes from a faulty thermometer. It's reading about 5 degrees too low. Even with that, I was on the high side of my mash temps. Planned was 154, dropping to 152 over the ~60 minutes. First temp reading after adding my strike water and mashing in was 158 ( which was actually closer to 163 thanks to the thermometer ). Let it go for ~60 min, and it was still at 155 after the hour.

Everything else went well, and I pitched with US-05 yeast and it's been fermenting for about 3 weeks at about 64F. Took my first reading at 2 weeks, and then every other day since. It's been solid at 1.022 for the past week. It should have finished up around 1.012-1.016 or so, according to the calculations. Would the overly high mash temps result in enough unfermentable product to lead to that high of a FG?

I'm thinking that's all I'm going to get, as due to the high mash temps, I created more unfermentable wort than normal. It's still tastes good, nice hoppy flavor, good malt to balance it, and has a bit fuller mouthfeel. It's definitely a very drinkable beer. Maybe not quite as high ABV as the plan, but still very adequate (5.5% vs 6.1%).

Next brew-day, have a new thermoworks digital thermo, and won't hesitate to add some cooler water, if I overshoot again on my strike water.

Any other thoughts, or similar experiences from anyone else?

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Old 04-22-2013, 06:46 PM   #2
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Yes, the higher mash temps would lead to more unfermentables and a higher FG.

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Old 04-22-2013, 06:46 PM   #3
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The high mash temps activate different enzymes that convert the starches in the grain into a higher percentage of complex, long-chain sugars that yeast can not eat (compared to lower mash temps where the starches are converted to almost all simple, short-chain sugars).

So you're right on with your thinking. That higher mash temp lead to more long-chain sugars in the wort that the yeast will not convert to alcohol, so higher FG, more residual sweetness in the final beer, which isn't always a bad thing in an IPA.

You are probably at FG. It doesn't hurt AT ALL, to go ahead and let it be for a few more days, then finish it out.

Good luck!


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