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Background: My co-brewer (ScottyG) and I recently brewed our first all-grain in a converted Coleman cooler. We have over sixty batches of extract under our belts and have even made a few hard ciders and a batch of mead. I freely admit, we are a bit late in getting around to going all-grain, but we’ve learned a LOT in our 60+ batches of extract+steeping grains.

We didn’t have high expectations for the first batch. We did some experiments to approximate temperature drops in the cooler (surprisingly little) and made sure we were using proper procedure. (following via ScottyG) *We used 10# of grain (9# Marris Otter, 1# Simpson's Dark Crystal) and 1.5 qt/lb for both mashing and sparging. Doughed in at 153, added 1 pint of boiling water. We let it rest for 60 min and the final temp was 149 F. Sparge water was 168 F, and we let it soak for 20 minutes before draining.

We did not: 1) Test pH 2) Test with iodine

First runnings were 2.4 gal @ 1.054, second runnings were 4.6 gal @ 1.012. Final was 7.1 gal @ 1.026 for an efficiency of 50%.* Much lower than we had expected, much lower than our software or hand calculations projected. The first running was about the SG we expected from the second.

We used some pre-crushed grain that was about a year old. (crushed at Northern Brewer about a year ago). It was from a kit a friend bought for us to make and had mistakenly got all-grain. We are reasonably certain that our troubles come from old grain, crushed a year ago. (BTW, we augmented with some extract to bring the resulting beer up to an acceptable SG. (Yay, it’s gonna be a beer!)

Now after all that setup, here’s the question:

What effect does the age of the grain have on the amount of fermentables you can mash out of it? Does the crush decrease the “freshness window?”

TL;DR What effect does old grain have, especially if it was crushed in the past.

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I love your attitude and comment "Yay, it's gonna be a beer!". I've made some bad mistakes in the process before, missed ingredients, and I've told people, worse case scenario, it's a beer! –  Mlusby Feb 4 '11 at 14:52
    
@Mlusby, I disagree. I've had a few batches that I screwed up pretty bad. Like the hoppy beer that I added all of the hops at 60 minutes (including the hops for the 30, 15, 5, and 0 minute additions). Could. not. drink. It was beer, but could not drink it. 5 gallon offering to the Beer Gods that I remember hop schedules on my future brews. –  Pulsehead Feb 4 '11 at 19:23
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4 Answers

up vote 1 down vote accepted

What I have heard about malt that is old is that the conversion time may increase due to decreased or degraded enzymes. It will potentially yield as much sugar as usual but may take an extra 30-60 minutes to fully convert. If this is the case your 60 minute mash may have only converted a portion of the starch.

You have also used too much sparge water since your final volume is 7.1 gallons, if you would have only collected 5.5 gallons your gravity would have been much higher. You essentially watered down your beer.

The design of your mash tun may have also played a part in the decreased efficiency.

Taking all of these things into consideration this would explain your low gravity outcome.

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How was the crushed grain stored?

It possibly soaked up ambient moisture, due to high relative humidity. Since it was crushed, it had more surface area to absorb the water.

There was some discussion of humidity and efficiency on Brew Strong, a few years ago.

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The crushed grain was sealed in a plastic bag, very little headroom. Cool, dry environment, no sunlight. –  TinCoyote Feb 4 '11 at 14:33
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ScottyG here. BTW we used 10# of grain (9# Marris Otter, 1# Simpson's Dark Crystal) and 1.5 qt/lb for both mashing and sparging. Doughed in at 153, added 1 pint of boiling water. We let it rest for 60 min and the final temp was 149 F. Sparge water was 168 F, and we let it soak for 20 minutes before draining.

We did not: 1) Test pH 2) Test with iodine

First runnings were 2.4 gal @ 1.054, second runnings were 4.6 gal @ 1.012. Final was 7.1 gal @ 1.026 for an efficiency of 50%.

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Information like this is good for explaining the original question. You will probably want this either added to the original post, or in a comment to the original post. Answers that aren't answers float to the bottom and get ignored. –  Mlusby Feb 4 '11 at 14:42
    
ScottyG's more precise comments added to original question. –  TinCoyote Feb 4 '11 at 18:47
    
Why did you let it soak for 20 min. before draining? Were you batch sparging? If so, did you stir well before the runoff? –  Denny Conn Feb 4 '11 at 21:17
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ScottyG again.

To NB Chris: I calculated the 50% efficiency based on 7.1 gal @ .026 points...if we'd have used less sparge water, we would have gotten fewer gallons but should have left more sugar in the grain. The 1.012 from the second runnings appears to be all that was available. We didn't worry about the high volume because we boiled most of the excess off anyway.

To baka: The 10# of grain was as measured by Northern Brewer when it was purchased. I didn't re-weigh it, but we didn't correct for that anyway.

To Denny: We batch sparged. I have seen different sources suggest that letting the sparge water sit for a bit can help ensure you get the last bit of sugar out of the grain, and we figured that worst-case, it was 20 minutes lost if it didn't help. We did re-stir the grain bed what I thought was well. I tasted some of the grain after we finished draining it and it wasn't particularly sweet anymore, so I think we were able to wash out what sugars were released.

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So it's possible that you had been shorted some grain from NB? –  baka Feb 5 '11 at 13:35
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