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Researchers hit on an unexpected tool to extract 80% of protein from beer waste: microwaves


Researchers hit on an unexpected tool to extract 80% of protein from beer waste: microwaves

Spent barley, which amounts to 36.4 million tons of landfill waste each year, could provide an alternative to meat protein—and simultaneously tackle food waste.
April 26, 2024

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Each liquid pint of beer we drink produces almost as much solid waste: in fact, the brewing of beer generates 36.4 million tons of leftover grain each year, most of which is heaped onto landfills, where all it does is rot and release copious amounts of methane into the atmosphere. 

Now, researchers say that they’ve chanced on a solution to this enormous and needless waste—and oddly enough, their approach uses microwave energy to extract over 80% of the protein that remains in nutrient-rich barley byproducts, for reuse in our diets.

Writing in a recent study, the team of scientists from Nanyang Technical University, Singapore, detail how they applied a technique called microwave-assisted three phase partitioning (MATPP) to accomplish this feat. First, they sourced some barley waste from a brewery in Singapore, then fermented the mixture, a process which starts the breakdown process in the grain that’s essential to isolate proteins. After that, the barley was dried and ground into a powder, then rehydrated. The next crucial step was to microwave the product, and then strain it, to isolate the crude barley mix. 

After microwaving, the researchers applied the rest of the method, called three phase partitioning. TPP is an emerging technique that uses liquid solutions containing different active ingredients to separate elements in a mixture. As a method, TPP isn’t completely novel in experiments. But few have considered how adding heat might change things. This allowed the researchers to investigate a hunch that microwaving would help to grease the wheels a bit and eke out more protein from the mix.


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Their hunch, it turns out, was right. When they compared the microwave-assisted TPP process with regular TPP on the barley mix, they found that with microwave power, the process was able to extract double the amount of protein—82.2%—compared to just the TPP method alone. From one kilogram of grain, they were able to extract 200 grams of protein—not bad for something that would ordinarily have ended up in the bin.

They think the reason for the high protein extraction is twofold: heat helps to loosen proteins in a mixture, which makes it possible to eke more out of a substance. Heat also breaks down hydrogen bonds, so weakening the cell wall in plants, which allows more of the solvent in the TPP mixture to seep in and release proteins from the grain. 

As the researchers discovered, it wasn’t just that their method unleashed more protein from the spent barley: a volley of additional tests showed that the grain exposed to MATPP contained higher levels of antioxidants like phenolic acid, likely due to the same traits that released more protein content too.

Spent barley from beer production is about 30% raw protein: the researchers think that this large untapped resource could be a valuable plant-based protein alternative to meat, as the world shifts away from these foods. What’s more, they could be added to cosmetics for their exfoliating properties, and their high antioxidant levels, which can help to increase the shelf life of different products without the traditional use of harmful chemicals. 

Now, these are both commercial possibilities that the team of scientists is looking into as they move forward with this research. “Protein extraction from agricultural side streams is a field primed and ready to be tapped,” they say

Chai et. al. “Recovery of antioxidative protein hydrolysates with functional properties from fermented brewer’s spent grain via microwave-assisted three phase partitioning.” Innovative Food Sciences and Emerging Technologies. 2024.

Image: ©Anthropocene Magazine

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