By Jacob Webster-Jones

 What do pancakes, mushrooms, and biofuel have in common? This may seem like a setup to a bad joke but actually they can all be produced by using a waste product of the brewing industry. You may have already seen some products from smaller companies advertising spent grains in lower carb or high fiber baking mixes at your local grocery store but this byproduct of the brewing industry has a variety of uses beyond the substitution of flour.

How Do We Get Spent Grains?

Before we get into the uses of spent grains, it would be useful to know what exactly spent grains are and how they’re made. Since spent grains are a waste product of the beer brewing process, you have to start by making beer. Let’s briefly go over the beer brewing process. First, grains are cleaned and sorted before undergoing the malting process (steeping, germination, and drying) before being stored for further use. These processes are done to activate enzymes within the grain. During mashing the grains are added to a vat of water and heated between 37-38°C to promote enzymatic hydrolysis of the malt constituents. This step produces a sweet liquid called the wort which contains much of the soluble content of the grains; this is what will be fermented and become beer. The wort is then filtered through the solid grains several times to extract as much of the soluble sugars as possible in the lautering step. The solid grains are then removed and are known as spent grains because they become waste after the lautering process and before the wort is fermented in tanks. The grains are typically then used as animal feed due to its price, high nutritional value, and effectiveness at improving yield [1, 2].

So What’s Left?

Once all the required portions of the grain are extracted, the spent grains consist of cell wall residues from the husk, pericarp, and seed coat; water insoluble proteins; some hop residue if those were added during the mashing step; residual sugars that weren’t extracted; and non-malt fermentable sugars. As you can see this “waste product” still has a lot left in it with some pretty interesting uses as a raw food material, energy production, and biotechnological processes [1, 3, 4].

Direct Food Ingredient

As was previously mentioned, brewer’s spent grains are currently used as a source of animal feed, so why are they not used as human food? Brewer’s spent grains are a cheap and abundant source of protein and fiber that can be used as an ingredient in baked goods such as pancakes, breads, and cookies. These baked products stand out from their traditionally made counterparts by their higher protein content (swapping out 10% of all-purpose flour with spent grains has been shown to increase protein content by 50%^A) and decrease in overall calories (~7% less) because most of the sugars have been extracted from the grain.

Photo by cottonbro from Prexel

So, all the good comes with some limitations. The color of spent grains depends on the grains being used and is not easily masked so it’s not the best if you want to make anything that doesn’t have a brown hue to it. Another thing to keep in mind is that this is not a one-to-one replacement for flour from a functionality and flavor standpoint, the lack of gluten in the grains means that you’ll have to supplement with conventional flour or use another binding agent like xanthan gum to keep the food from instantly crumbling. Perhaps the biggest limitation is the flavor of the grains, to put it lightly, it isn’t great. I made cookies with spent grains that I had after home brewing and fed them to my roommates. I had feedback from, “this tastes like sweet bark”, to, “you know when a kid makes a ‘cookie’ out of mud and grass, that’s what this tastes like.” To reduce the perception of objectionable flavors, it’s best to use anywhere between 5-10% (baker’s percent) of spent grains in a given recipe.

Further processing

The possibilities of brewers’ spent grains don’t stop there. Xylitol, lactic acid, phenolic acids, microorganisms, and a wide variety of enzymes take advantage of the high nitrogen content in spent grains [1] and can be produced efficiently without a significant increase in production costs [4]. The application of spent grains reaches beyond the food industry; spent grains can be used as fuel through combustion or fermentation which can be used in the brewery [1, 4]. The porosity, low ash content, and high amounts of fibrous materials in spent grains also make them a good alternative component in bricks as well as a metal adsorbent to clean wastewater [1].

Feasibility & Sustainability

Unfortunately, we live in a world where something just being an interesting concept isn’t enough for companies to do it, it has to make sense fiscally and more recent times it has to make sense environmentally. You can find some small companies who use them but it hasn’t quite caught on with the larger brewers yet. A study conducted in Brazil compared different levels of integration and purpose of spent grain within a brewery to see what would be the most cost efficient and environmentally friendly way to implement upcycling into the plant. They found that, surprise, surprise, the more integrated (more parts of the process are using recycled materials), the more environmentally friendly the process and that production of harmful secondary products was minimal. This paper only looked at a handful of plant set-ups and even the authors noted that there are better ways to set up a brewery to make it run more efficiently and more environmentally friendly [4].

References

1. Mussatto, S.I., G. Dragone, and I.C. Roberto, Brewers’ spent grain: generation, characteristics and potential applications. Journal of Cereal Science, 2006. 43(1): p. 1-14.
2. McCarthy, A.L., et al., In vitro antioxidant and anti-inflammatory effects of brewers’ spent grain protein rich isolate and its associated hydrolysates. Food Research International, 2013. 50(1): p. 205-212.
3. Stojceska, V., Chapter 16 – Dietary Fiber from Brewer’s Spent Grain as a Functional Ingredient in Bread Making Technology, in Flour and Breads and their Fortification in Health and Disease Prevention, V.R. Preedy, R.R. Watson, and V.B. Patel, Editors. 2011, Academic Press: San Diego. p. 171-181.
4. Mussatto, S.I., et al., Techno-economic analysis for brewer’s spent grains use on a biorefinery concept: The Brazilian case. Bioresource Technology, 2013. 148: p. 302-310.

Jacob Webster-Jones | Linkedin

SMF Blog Writer

Jacob found his passion for food science while on an elementary school field trip to a R&D lab in San Antonio, Texas. Since then he has been interested in why food behaves the way it does and how it can be used to improve people’s quality of life. He is currently pursuing his bachelor’s degree in Food Science & Technology from Texas A&M University and is the current president of his school’s food science club and IFTSA chapter. After he graduates, Jacob plans on going to work for a few years before returning to start a graduate degree, his ultimate goal is to work in research and development for a flavor company. On the off chance he has free time you can find him experimenting in the kitchen or enjoying the outdoors.