Spent grain is the term given to grain that is left over after the beer making process. When brewing beer, you add grain to hot water to extract all of the sugars in a process called mashing. The resulting sugar water is called wort and is then boiled with hops. After mashing, the grain can be composted, fed to livestock, spread in garden beds or, as I like to do, dry it out and turn it into a flour.
Spent grain flour gives your bread an incredible boost of whole grain flavor and nuttiness that really takes your bread to a different level. I like to use between 5-10% spent grain in my bread. For example, if I bake a 500g loaf, I’ll use 450g bread flour and 50g spent grain flour. Making spent grain flour is extremely easy and can be done while you finish your brew day.
Step 1: Brew some beer!
The first thing you’ll need to do is brew an all-grain or partial-mash beer (or know a brewer and get some fresh spent grain from them). I brewed up a cocoa porter and am using the grain from that beer in this guide. I’m hoping some of the darker and chocolate malts will carry through some of their roasty flavor into the bread I use the flour in.
There are many different ways to mash your grains and in this particular beer I chose to do a brew in the bag (BIAB) method with a sous vide to maintain my temperature. I normally use a large 10 gallon mash tun but this is only a 3 gallon batch so it’s easier for me to do it this way. I mashed the grains for an hour at 151’F and then did a mash-out at 168’F for 10 minutes.
Step 2: Remove all wort from grain
After mashing you’ll want to strain all the wort from the grain. When I’m using the BIAB method I let the bag rest in a colander for about 10 minutes so all of the wort can drain out. While this is happening, preheat your oven to 225’F and get some baking sheets cleaned and ready.
Step 3: Transfer grain to a baking sheet
A large baking sheet can handle about 5-6 cups worth of spent grain. Spread the spent grain in a layer about 1/4-1/2″ thick on the baking sheet. The thicker the layer, the more you’ll have to toss the grain and the longer it will take to dry out.
Step 4: Bake at 225’F until grain is completely dry
This will vary a lot depending on oven temperature, thickness of grain in the baking sheet, how dry your grain was to start with, etc, but I’ve found that at 225’F it will take about 3-5 hours to dry out.
You’ll definitely want to toss the grain around several times throughout the drying process and also rotate the sheets from top to bottom if you’re using multiple baking sheets. You can tell the grain is dry when it’s crunchy and there aren’t any darker clusters when you’re tossing it around.
Step 5: Grind the dried grain into flour
After you’ve dried your grain and made sure there isn’t any moisture left, it’s time to grind your grain into a flour. You want to make sure your grain is as dry as possible or else your flour could spoil and go rancid if you don’t use it right away.
I use a cleaned out coffee grinder to turn my dried grain into a flour. I simply fill the coffee grinder with flour and pulse it for 15-20 seconds, then dump it into a mixing bowl.
Note: If you don’t have a coffee grinder or don’t want to turn it into flour, you can use this grain as-is in your bread. I would still limit the whole dried grain to about 30-50g in a 500g loaf of bread.
The flour will still have some texture to it after going through the coffee grinder. Personally I like this and feel like it adds something to the bread but if you want a true flour then you might want to look into a flour mill.
I started with 11 cups of spent grain going into the oven and ended up with just over 3 cups of dried flour. I put mine in a sealable plastic container where it will last for several months. If you aren’t going to use it for a while, I’d recommend storing it in the freezer.
Step 6: Bake some bread!
Now all you have to do is bake some bread with your freshly made spent grain flour! Here are some of my spent grain bread recipes:
I’ve also thrown this, in small amounts, into pizza crust and quick breads (like banana bread). Anywhere you want a boost of whole grain flavor, throw some of this spent grain in there and enjoy! Let me know how you use your spent grain flour in the comments below!