As a homebrewer living in a small Manhattan apartment spent grain is….the worst. It’s heavy, it’s messy, and it makes me feel really wasteful. “This has to be like….25 loaves of bread?!” I always think to myself as I slowly scoop out the oatmeal-like jumble until it’s light enough for me to dump the whole mash tun into a trash bag.

Wooden bowl filled with spent grain flour next to a small marble bowl of spent grain — Spent grain flour with the grain it was made from.

But, my guilt laden fantasies aren’t completely true because there is almost no gluten in spent grain. That means those 25 imaginary loaves of bread would really suck. But on the bright side I can save grain, turn it into flour, and eat it after all! Another small victory for the homebrewer 🎉

How to Make Spent Grain Flour

The below short video shows you exactly how to make spent grain flour. Starting from mash tun all the way to ending up in your measuring cup. There is also a recipe-style explanation of this process at the very bottom of this post. If you don’t want to nerd out on the properties of spent grain with me…scroll all the way down. Geeks, I’ll meet you below the video!

What is Spent Grain Made Of?

If you did your job as a brewer, not much sugar or starch! The heat and enzymes in the brewing process gelatinzes the starchy endosperm in a kernel of barley. Without the sugary center bits, spent grain is made up mostly of grain’s husks. There is an external husk and two internal husks/cuticles called the pericarp and the testa.

The inside of a barley kernel before it is spent grain — Here the embryo is dyed red. The husk, pericarp, and testa make up the brownish outer layer.

Knowing this it makes sense that spent grain is roughly 70% fiber and 20% protein as these are the building blocks of the tough outer wall of the kernel that protects the soft starchy layers. These husks contain a high concentration of arabinoxylan and cellulose, two very healthy dietary fibers. They are even linked to controlling the onset and symptoms of diabetes.

Spent Grain and Baking Research

A study researching the validity of using spent grain to bake breadsticks (science is fun!) found a specific brewery sample of dried spent grain to contain exactly: 5.6% moisture, 20.8% protein, 4.5% fat, 3.2% ash (“ash” is mineral content), 3.3% starch and 60.5% dietary fiber. Compare that to the typical makeup of wheat flour: 74% starch and 4% dietary fiber, and it’s pretty clear that spent grain flour isn’t much like conventional flour at all!

Beyond the very high fiber content, spent grain flour differs from conventional flour in another very important way: There is almost no gluten in spent grain. This means the flour can’t form its own protein structure when it reacts with water and it will not rise, spread or hold a shape. In fact, professor Michael J. Lewis at UC Davis wrote an informative paper explaining that barley itself contains almost no gluten. Therefore, beer could be considered safe for Celiacs (people with gluten intolerance). I won’t get into that here, but it’s a good read if you’re interested.

Picture from thespent grain breadstick study published in the International Journal of Food Science and Technology in 2012. — Picture from the breadstick study published in the International Journal of Food Science and Technology in 2012.

You can see that lack of structure here. While the percentage of spent grain in the breadstick increases the structure or “crumb” of the bread decreases and eventually collapses completely at 35% spent grain flour.

Using Spent Grain Flour in Traditional Recipes

This is why treating spent grain flour like a nut meal or gluten-free flour in recipes works MUCH better than replacing any kind if all purpose, self rising, bread, cake, or wheat flour. If you want to throw a little spent grain into a traditional recipe, replace no more than ¼ cup per cup of conventional flour and add ¼ more leavener (baking powder/baking soda, skip this for yeast). So, if muffins call for 1 cup of flour and 1 teaspoon of baking powder you can use ¼ cup spent grain flour and ¾ cup all purpose flour with 1 ¼ teaspoons baking powder. But, expect your muffins to be less fluffy and more like a bran muffin – fiber! Hurray!

And before you bake with spent grain flour at all, take a look at my video so you can ensure your flour is milled to the correct texture. Let me save you hours of flossing out the grit of an unrefined spent grain flour, please. Learn from my mistakes.

All in all, it’s about having fun baking! Try my recipes that have been tested multiple times with spent grain, or go on your own journey experimenting with this less-than-flour like “flour” as I have for the last year and a half. If you run into issues you can find me @beerswithmandy…but if you make cookies heavy as bricks because you replaced all the flour…I might just have to say, “I told you so!”

Recipes that Use Spent Grain Flour

I’ve been baking with spent grain flour for close to a decade now, below are my tried and true recipes for using up the gluten-less, fiber-full flour.

Two spent grain brownies topped with cookies and cream ice cream — Spent Grain Brownies

spent grain banana muffins made with spent grain flour — Spent Grain Brownies

Grit-Free Spent Grain Flour Recipe

Dehydrate the Spent Grain:

Scoop enough flour out of your mash tun to make ¾ inch layer of grain on your baking sheet.
Break up as many clumps in the grain as you can. These retain moisture and take longer to dry.
Place the baking sheet in a cold oven and turn the oven to 350°F.
As soon as the oven reaches 350°F, remove the baking sheet and stir the grain. It will be very steamy! Then smooth it into a single layer and return the baking sheet to the oven.
Turn the heat down to 180°F.
Every hour, remove the sheet. Carefully feel through the grain for clumps you can break up with your fingers. Then give the grain a stir and return it to the oven.
After 5 to 7 hours the grain should be very dry and crumbly, easily breaking between your fingers.

Grind the Spent Grain into Flour:

Put your grain into a blender. If you’re using a very large baking sheet or multiple baking sheets, you may have to do this in batches. The blender should be a little over half full. Pulse the grain on high. Regularly remove the container from the base and give it a good shake. This is especially important if the blades gets stuck.
Grain that is too wet will form clumps or balls. It needs to go back into a 180°F oven to dry out more. Check it every 20 minutes to avoid scorching.
At first, the grain will form a flour made out of elongated granules. (I think they look like tiny sticks or pieces of hay.) Do NOT stop blending the flour yet. Continue to pulse and shake until the flour has a consistency of very fine sand or silt. (I know it doesn’t sound appetizing but this is important!)
Pour the grain into an airtight container. If any flour sticks to the sides of the blender after a little tap, leave it! The stuck grain likely contains moisture.
Use within 1 month or store in the refrigerator or freezer for up to 3 months.

How to Make Spent Grain Flour (That You Can Actually Bake With!)