Breaking Bread: How to Mill your Spent Grain

So, you’ve just finished homebrewing and now you’re staring at a huge pile of spent grain wondering what do do with it. Worst case, you could just throw it away, but that would be a waste of a perfectly viable product. Or you could continue the “cycle of life” by composting it, ensuring the spent grains of the past may contribute to hops of the future (should you use the compost on your hop rhizomes). Personally, I’ve traded with a good friend of mine who raises chickens; he gets free chicken feed and I get a dozen or so fresh eggs. Win-win if you ask me.

In my opinion, the best case scenario is that you can eat it. While spent grains have given up much of their sugars and proteins to the wort, they are still viable as a food product. Most often, people end up using spent grains to bake. A couple I met while at Avery Brewing Company in Boulder, Colorado swore by the spent grain pancakes they make.

How you use your spent grains will ultimately depend on what you’re using them for. The method we’re explaining below is just one way to process them, but I’ll let David explain further.

How to Mill your Spent Grains

You’re probably asking yourself why you’d want to mill your spent grains in the first place? Didn’t we mill them ahead of time for brewing? Well yes, that’s true. You don’t have to process your spent grains any further but this method gives you more versatility and possibly the ability to incorporate spent grain into a favorite recipe yours. In many of the recipes I develop and post, this process will be used to mill spent grain into flour or meal depending on the application and desired characteristics in the final product.

Step 1: Dry Out Your Spent Grain

This part of the process will take up to 24 hours. What you want to do is take your spent grain and place them in a, or possibly a few baking sheets or pans large enough to hold them. Pre-heat your oven to 150-200° F. Once there, place the spent grains into the oven. Stir the spent grains every hour to redistribute moisture and aid in drying. Once they’re completely dry, you can either store them in a plastic bag or airtight container to mill later or move on to Step 2 to continue the process.

Drying out spent grains does a couple of things. First, drying creates a lower water activity and it gives the grains a prolonged life span. You might not have the time or inclination to use spent grain in your cooking right away so this gives you the ability to use these grains when you’re ready (freezing would be the next best method). Second, it is necessary to dry them out in order to mill them to consistency we’re looking for. Any moisture will cause bending or mashing of the grain and inhibit them from achieving a flour-like texture.

Tray of dried out spent grain from a previous homebrew.

Tray of dried out spent grain from a previous homebrew.

Step 2: Mill your Spent Grains in a Blender

Can’t I use a food processor? You might be able to, but using a blender is more efficient for a few reasons. First, the way the blender works is that it creates a vortex that sucks ingredients back down onto the blades whereas a food processor tends to knock ingredients outwardly against the wall of the container. Second, the variable speeds allows you to break down the grains (husks and all) into a spent grain flour. In my opinion the blender is superior for milling but there are of other commercial mills available that are more efficient and provide a more consistent product.

Place several ounces of dried spent grain into your blender. Put the lid on and blend on medium-high/high speed for several minutes. The grains will be reduced into a coarse flour at this stage with finer particles being sent airborne so you’ll want to keep the lid on to avoid breathing it in.

Place several ounces of your spent grain into a blender.

Place several ounces of your spent grain into a blender.

You'll want to keep the cover on during the blending process as the spent grain turns into a fine powder.

You'll want to keep the cover on during the blending process as the spent grain turns into a fine powder.

What your blended spent grains should look like.

What your blended spent grains should look like.

Step 3: You’re Done!

As you can see, this was a pretty simple process. Take your spent grain flour and store it in an air tight container. Since the dried grain is shelf stable you’ll be able to keep it with your other baking supplies so you won’t forget to grab some for your next recipe. The photo below illustrates the contrast between whole, dried grain and a fine, milled flour.

Before and after: on the left, dried out spent grain'; on the right, blended spent grain.

Before and after: on the left, dried out spent grain'; on the right, blended spent grain.

Now What?

So now you have several ounces (or even pounds!) of spent grain flour. What can you use it for? Spent grain flour has lost much of the protein, gluten, and sugars necessarily for baking with this exclusively. It does, however, have a healthy dose of fiber to offer. That said, you can use spent grain flour in much the same way you’d use other grain flours or baking adjuncts, if you will. Use spent grain flour as a coating for fried green tomatoes or as additional texture for breads. Just remember your flours will lend a flavor similar to the recipe you brewed so some will be more appropriate to use in a recipe than others.

Hopefully this was helpful in explaining how and why this needs to be done. Many future recipes will be referencing the use of this product…Be on the lookout for the next post.

Now, go brew so you have grain to use!

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3 Responses to Breaking Bread: How to Mill your Spent Grain

  1. Ryan Moore says:

    I am an artisan sourdough baker. I have used spent grain from my homebrew in sourdough breads, muffins, and crackers. I have never milled it tho. Always used the whole grain. I like the texture it gives. But i will need to try this out for people not into a whole grainy mouth feel.

  2. Gunter Pfaff says:

    It was fun reading this blog after I thought I had pioneered the milling of spent grain.
    Humbled now, I still want to report that I dried spent rye in a dryer for 24 hrs, then milled it in a VitaMix and used 1/3 cp of it instead of the same amount of rye flour in my usual whole wheat/rye bread and it tasted great. The spent rye came from making rejuvelac for vegan cheddar cheese.

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