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Recycling beer waste

When you crack open a cold beer at the end of a long day, food waste is probably not on your mind. But the process of making beer generates massive amounts of leftover grain – and researchers from Virginia Tech in the US have just developed a new way to use it.

Once the flavour has been extracted from barley and other grains, what’s left over is a wet powder mostly composed of barley malt grain husks. Called brewers’ spent grain (BSG), this byproduct is rich in protein and fibre. Every 100L of beer brewed generates 20kg of wet BSG – adding up to around 40 million tonnes per year worldwide. As craft brewing becomes more popular, it adds even more waste to this figure.

“There is a critical need in the brewing industry to reduce waste,” notes Haibo Huang, food scientist and project lead from Virginia Polytechnic and State University.

Currently, BSG is typically used as low-value livestock feed or dumped in landfill. This seems like a waste of a cheap, abundant, and nutritious product that could be added to human foods. But there’s a problem: the high fibre content (70%) makes it difficult for humans to digest.

Huang has been investigating how to transform BSG into a more functional product, along with co-author Yanhong He, also from Virginia Tech.

“Spent grain has a very high percentage of protein compared to other agricultural waste, so our goal was to find a novel way to extract and use it,” He explains.

As described in a study presented at the spring meeting of the American Chemical Society, the researchers developed a new way to separate the protein in BSG from the fibre – without drying the grain first, as other techniques require.

The study tested three commercially available enzymes (alcalase, neutrase and pepsin) and discovered that alcalase most efficiently separates out the protein and fibre components without losing large amounts of each, resulting in a protein concentrate and a fibre-rich product.

The protein concentrate retained 83% of the protein in the spent grain. The researchers suggest that this could be used in food product, responding to the increasing demand for alternate protein sources. BSG could be ground up into a powder that could act like flour in baked goods; some breweries even use BSG in recipes in their restaurants. The fibre product, on the other hand, could be used in biofuels.

But it’s still early days. The separation technique must be massively scaled up to deal with the enormous volume of beer waste generated by the brewing industry, and since the enzymes used are expensive, the researchers are also exploring how to make the process economically viable.

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