Spent Grain Flour

So, there I was, merrily writing away on how to make spent grain bread when I realized something important. The recipe calls for spent grain flour. And I hadn’t written how to make spent grain flour at home…

Thus, deciding I didn’t want to do this backwards, you’re just going to have to wait a few more posts for the spent grain bread recipe. This is a good thing, actually. I promise. It means you can both learn more about how you’re going to make this fine bread AND I can experiment yet more on how to make sure it’s delightful.

Plus, don’t you need to plan your brew day so you can get some spent grain?1

Anyway, on to making flour. What I do is a slight modification from what the fine folks at Brooklyn Brew Shop do to make their spent grain flour. I suspect, from reading it, that they don’t tend to process as much grain down into flour as I do. Not that they don’t have as much grain; they likely have more. But that they tend to process down in small amounts as needed. For me, it’s much easier to store as flour, and most usages call for flour, so I tend to dry and mill all of my grain.


Turn on your oven as low as it goes. If you have a dehydrator, that works too, but definitely use some heat (not just “fan”). Spread your grain on a cookie sheet or “fruit roll-up sheet” (dehydrator; keep the grain from falling through the slats)2 Put it in the oven or dehydrator.

This is going to take forever in the oven and forever times two in the dehydrator. Accept this now. The thicker you spread the grain, the more you can get in the oven at once, but the longer it will take. And the more likely for odd smells. I’d say 1/4 inch to 1/2 inch deep is your best bet.

Plan to dry your grain for a minimum of six hours. Stir it occasionally. Spent Grain Chef says once at four hours. I am incapable of leaving it alone that much. Frankly, I think stirring it more often makes it go faster. But this is not based on any level of scientific study. This is just my guess.

Dry spent grain should be easily pulverized between two fingers. No squishiness or smooshing. Attempting to squish it should result in dust. Spent grain chef says, “when you feel absolutely no moisture remaining.” This is how I test for that.

In small batches, grind the flour down in your blender. It will make a horrible clatter. Everything is ok. This is the best way to the finest flour. You can try to do this in your food processor, but the flour will be coarser and you will make make a bigger, dustier mess.3

Store in an airtight container. I don’t know how long it keeps; it hasn’t gone off on me yet. Substitute 1:1 for all-purpose flour in any recipe you want to experiment with, but I suspect it’d go poorly if you replaced all the wheat flour. I suggest starting at roughly 10% of the flour and finding out what you life from there.

1 Also beer, but whatever.

2 I’ve also used parchment paper in the dehydrator. It works just fine, but isn’t as convenient or sturdy as the pre-made sheets. The sheets also assure airflow by constraining how far to the side you can put grain. My parchment did not. Seemed fine.

3 Maybe that’s just mine. But I doubt it.

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