It has long been assumed that coffee by-products — coffee grounds and coffee silverskin — have few practical uses and applications.
But recently, scientists have discovered that antioxidants aren’t just in the brewed coffee — they’re also in the used grounds. But we only just learned how nutritionally rich a source they really were.
Finding even more uses for coffee grounds
For years, used coffee grounds have been used as plant fertilizer, insect repellent, homemade skin exfoliants and as abrasive cleaning products, among other things.
People around the world drink millions of cups of coffee every day, generating about 20 million tons of used grounds annually. Although some spent coffee grounds find commercial use as farm fertilizer, most end up in trash destined for landfills.
Coffee itself is a rich source of healthful antioxidants, so Maria-Paz de Peña and her research team wondered about the amount of antioxidants that remained in used coffee grounds from different coffee-making methods. They wanted to figure out the total phenolic content in extracts from these leftovers.
Their 2012 report in ACS’ Journal of Agricultural and Food Chemistry concluded that found that filter, plunger and espresso-type coffeemakers left more antioxidants in coffee grounds, while mocha coffeemakers left the least.
Because filter and espresso coffeemakers are more common in homes and commercial kitchens, the authors report that most grounds are likely to be good sources of antioxidants and other useful substances. They note that after these compounds are extracted, the grounds can still be used for fertilizer.
Antioxidant effects of coffee by-products 500 times greater than vitamin C
Apart from these limited applications, coffee by-products are by and large deemed to be virtually useless. As such, practically all of this highly contaminating ‘coffee waste’ ends up in landfills across the globe and has a considerable knock-on effect on the environment.
However, a UGR research team led by José Ángel Rufíán Henares set out to determine the extent to which these by-products could be recycled for nutritional purposes, thereby reducing the amount of waste being generated, as well as benefiting coffee producers, recycling companies, the health sector, and consumers.
In an article published in the academic journal Food Science and Technology, the researchers demonstrate the powerful antioxidant and antimicrobial properties of the coffee grounds and silverskin, which are highly rich in fiber and phenols.
Indeed, their findings indicate that the antioxidant effects of these coffee grounds are 500 times greater than those found in vitamin C, and could be employed to create functional foods with significant health benefits.
Moreover, Professor Rufián Henares points out, “They also contain high levels of melanoidins, which are produced during the roasting process and give coffee its brown color. The biological properties of these melanoidins could be harnessed for a range of practical applications, such as preventing harmful pathogens from growing in food products.”
However, he also adds, “If we are to harness the beneficial prebiotic effects of the coffee by-products, first of all we need to remove the melanoidins, since they interfere with such beneficial prebiotic properties.”
The researchers conclude that processed coffee by-products could potentially be recycled as sources of new food ingredients. This would also greatly diminish the environmental impact of discarded coffee by-products.