Some Food Science Related to Brewers’ Spent Grain

As I’ve immersed myself in beer culture, I’ve come to be incredibly aware of brewery waste. In particular, a brewery-in-planning specifically mentioned spent grain and its uses to me; until then I hadn’t really put much thought into it. That mention led Bill and I to make a few loaves of spent-grain bread, after which I became curious about the nutritional content of spent grain.

So I did what is practically second nature these days: I asked Google to help me figure it out. From various, long-unrecalled sources, I did discover spent grain has a lot of fiber (which I expected) and is high in protein (which surprised me).

I was most curious about micronutrients, though, which is how I ended up asking Google, PhD1 for further help. And, oh MAN, have I learned a lot. Mostly from reading (and rereading and rereading) a review article2 I found online (since taken down; and I forgot to note the access date) from Journal of Cereal Science titled, “Brewers’ Spent Grain: Generation, Characteristics and Potential Applications.”

After trying for ages to make a single post out of explaining this article, I’ve realized it’s going to take at least two, possibly three, posts to really break it down. Furthermore, I decided that there was one aspect, in particular, I found deeply fascinating, so I’m starting there.

Food. Of course. The most interesting uses to me are always going to be food-related.

I think this isn’t surprising, as I’m probably as invested in food as I am beer (if not more so). Indeed, once I started experimenting with spent grain as an ingredient in food, I realized I was far more interested in cooking with it than brewing the beer itself3. So my brewing equipment is a bit dusty, but my loaf pans are getting a workout.

So, what did I learn?

As I mentioned, I found this review by looking for the nutritional content of spent grain. So, while I don’t recall the first places I learned generically about fiber and protein content of spent grain, those facts were reiterated in this paper. Basically, when dried, milled into a flour, then baked into bread, the fiber content of the bread was doubled. On top of that, overall protein was increased 50% and the essential amino acids were increased by 10%4. Finally, the calories were decreased by about 7%; I assume due to the increase in fiber (the review authors don’t say). This is awesome, frankly. If nothing else, I can feel better about the bread I make. (Recipe up next week.)

However, like any awesome thing, there are some catches. The good news is that the catch isn’t in the nutrition, but in the use of the grain for making food products. The bad news is that there’re a surprising number of catches. The devil is, as they say, in the details.

The first catch is alluded to above, in that spent grain must be turned into flour before using, or at least the review authors claim. I’ve met homebrewers who make bread from whole spent grain, and Spent Grain Chef over at Brooklyn Brew Shop have a few recipes calling for whole spent grain. So, clearly, the statement that the grain must be milled down is not wholly correct. However, it seems likely to me that, on a large scale (thinking Budweiser amounts of grain here), flour is going to be substantially more palatable.

Ok, no problem there, right? Make that stuff into flour and throw it in everything! More fiber! Fewer calories!

Unfortunately, that’s the next problem. Apparently, spent grain flour bakes into a brownish color (I can vouch for this; and it gets worse the darker the beer you brewed), which means anything that needs to bake up perfectly white will not be well-suited to using any amount of spent grain flour to bake. To my mind, that’s not a huge impediment. So we won’t be making angel food cakes with spent grain flour, but chocolate chip cookies? HERE I COME.

On top of that, apparently there are flavor and texture issues. Sure, Spent grain flour can be substituted in major commercial applications, but for no more than about 10% of the flour in baked goods. I’d love to know more about this (and am trying to find the citation in question). Partially because I pretty much always love to know more, but also, because there are a lot of things that are different in a home batch than what the authors say is acceptable. Looking at my recipe (up next week!), I do substitute a bit over 10% of the wheat flour for spent grain flour (I use 1/9 spent grain flour, to be precise), but this is largely because it makes measuring easier. Everyone who’s had the bread agrees it’s wonderful, but the base recipe is pretty wonderful too. I think Bill and I will have to experiment with this. (And cookies. Of course.)

Ok. Fine, all’s well. We make it into flour, we put it in off-white goods, we keep it at only 10% of the flour content, and BAM! We still end up with increased protein, increased fiber, and decreased calories! Let’s do this. All we have to do is dry it out, right?

Indeed, but that’s another issue. Spent grain is about 80% water, and it spoils quickly. Having recently come into a bunch of spent grain from my homebrewing and from my homebrewing friends, I can attest to this spoilage problem. I found it easy to freeze, but if I tried to dry too much at a time (in the oven, specifically), the grain got a slightly “sour” smell to it5. On a home scale, this wasn’t really a problem. In fact, it lent a very nice (albeit quite mild) flavor to several of loaves of bread I made. On even a small professional brewing scale, though, this would add up to a lot of stink around the place (and not everyone finds brewing a pleasant smell to begin with). What I don’t know, and the review doesn’t get into (at least, that I understand), is if any pathogens can be growing on the spent grain while they “spoil,” or if it’s only a set of stink-makers. There are various chemical treatments that can be applied to the grain to keep it from spoiling while wet, and maybe they are cost effective for some uses, but drying the grain has the advantage of preventing spoilage while reducing volume and weight, making for easier transportation.

But drying takes up extra space, even if you go for freeze-drying (which is generally not cost effective, according to the review authors). So, to dry, we have to look to methods such as oven-drying. This is what homebrewers do if they’re drying grain to work with. Most home ovens only go as low as 170F – 200F, which is substantially higher than the 60C/140F the authors claim is the maximum heat grain can be dried at before the generation of “unpleasant flavours.” They don’t get into what such flavors are, and I haven’t been able to get my hands on the cited paper yet to find out.

But it does lead me to ask a few questions, possibly because I’m coming at this from a craft beer perspective and it’s clear the studies they are citing (and the breweries they are considering) are all much bigger. So one question I have about flavors during drying is whether the beer’s malt bill makes a difference. See, it’s clear that the authors of this review, & likely the authors of the primary research they cite, are thinking of what I’ll call “macrobrewers6.” These are, undoubtedly, the most important breweries to be considering as they generate the most waste. However, more creative uses for spent grain may well be found, or needed, by the smaller breweries who produce less grain and have a harder time supplying large dairies or other types of large-scale farming operations.

So, does drying the spent grain from a stout present major differences than drying the spent grain for a pilsner? Does the spent grain from a pilsner brewed wholly from barley present major, minor, or no differences from a pilsner brewed partially from corn and/or rice? I’m very curious. For the record, my guess is that stouts and other beers containing dark malts will cause more off-putting flavors, and more quickly, than spent grain flour from beers made exclusively without dark malts.

One thing the authors didn’t address was sun-drying the grains. While I can’t imagine attempting to do this here in Chicago or in Brazil (where the reviewers are from), due to the humidity, this has to be an option in some places. I’d be massively curious to know what this looks like, how long it takes, what the spoilage rates are, whether any off-flavors are produced, and so forth.

Flavor issues also lead me to wondering, how much of this is related to beer drinking? Do non-beer drinkers enjoy foods made from spent grain? For beer drinkers who like the food, is it related to the kinds of beers they like? I don’t even know how researchers would test this, but I’m hoping someone does at some point.

I’m currently experimenting with different drying methods. So far, no drying method has been discernibly different from any other once the dried spent grain is milled into a flour and baked into bread. I’ve tried oven drying at 170F or 200F, using a dehydrator at 140F or 160F, and a variety of combinations of the methods7. No one has mentioned noticing the difference. I can’t even detect the difference, and I make each loaf of bread (or pie crust). Even the “sour” funk I mentioned some of the grain has was barely transfered to the loaves. Noticeable, at least to me, but minor. The “dark malt bill” spent grains had an evident color difference, but not much flavor difference. (I expected the visiting nine-year-old to reject my bread based on color alone8.)

Everyone I’ve fed this bread to, in any form, has truly loved it. This is a good sign, but I wonder if that scales. Maybe I just have adventurous friends when it comes to food.

What do you think? Have you ever experimented with spent grain? What are you more curious about? What do you know from past experimentation? What do you currently want to experiment with? What are your favorite uses for spent grain? What would you like to know more about?


Mussatto, S. I., Dragone, G., & Roberto, I. C. (2006). Brewers’ spent grain: generation, characteristics and potential applications. Journal of Cereal Science, 43(1), 1-14.

1 Also known as Google Scholar. It’s a really wonderful way to seek out academic literature on a topic.

2 For those who don’t know, a review article is a summary of the current knowledge. This knowledge is gleaned from other publications (often termed “the literature”). Such an article also includes an expansion by the authors on what the findings mean, what directions future research could or should go in, what they believe the overall impact of this research is, and other ideas about the particular topic.

3 Good thing I know about 138,970 homebrewers. Bad thing they all know I love spent grain. I’m kinda swimming in it right now. But they share recipes too!

4 All proteins are made of amino acids. Most amino acids we can generate ourselves. However the ones called “essential” are so named because our bodies cannot produce them. We must get them from our food. Luckily, this isn’t a huge challenge, but it’s why there was a time when many of us were taught to eat “complete” proteins in a meal.

5 Yes, I know “sour” isn’t technically an aroma. I know I’m supposed to say “aroma” when I often say “smell.” However, sometimes you use your nose to smell things, and what you smell is so closely associated with sour that it’s all you can say you smelled.

6 Meaning the Budweiser & Miller-size brewers of the world. I kind of hate the term, as it sure seems like Boston Beer Company, Lagunitas, & more are fairly huge, but it seems to be the accepted term for that group.

7 Mixes were mostly based on trying to do it very carefully and precisely, and eventually going batty with impatience and frustration, and resorting to whatever was fastest.

8 I should have known better. As a four-year-old, his favorite food was cherry tomatoes. While I think that’s changed, he definitely snitched more than a few of mine while he was here.

2 thoughts on “Some Food Science Related to Brewers’ Spent Grain

  1. Great post Natasha! To be honest, I never heard of spent grain before I met you! Or at least, I never understood that it was a usable by-product of brewing. When I have a home kitchen again, it’s something I would definitely be interested in experimenting with; until then, I will eagerly follow your experiments!. Based on what you’ve said, I’m not surprised that spent grain, properly handled, works well in certain baked goods. I’ll be interested to hear how spent grain from different brews contributes to flavor and how you streamline working with it as a home cook.

    • Caroline, I can’t wait to keep experimenting with it. I have to be honest, it’s been fun. The only downside really is the quantity that comes from any amount of brewing.

      One of my friend, Jason, says everything he’s read advises that homebrewers not even try to keep up with the grain they produce. It makes sense, but it’s unfortunate given that for many, especially urban homebrewers, the only other choice is the landfill.

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