Writing in the Journal of Agricultural and Food Chemistry scientists from the University of Navarra, Spain, examined the antioxidant content of the coffee waste finding that a large amount of the antioxidants from coffee remain in the waste product.
Led by Maria-Paz de Peña, the research team found that filter, plunger, and espresso-type coffeemakers left high levels of antioxidants in coffee grounds, while mocha coffeemakers left the least.
“All spent coffee grounds, with the exception of those from the mocha coffeemaker, had relevant amounts of total caffeoylquinic acids, mainly dicaffeoylquinic acids … which were 4–7-fold higher than in their respective coffee brews,” said de Peña and her team.
In addition the researchers found that the used coffee waste contained high levels of other antioxidants in addition to extractable levels of caffeine.
“This study obtained spent coffee extracts with antioxidant properties that can be used as a good source of hydrophilic bioactive compounds,” explained the researchers.
De Peña and her team noted that the high levels of coffee consumed on a global level mean that around 20 million tons of used coffee grounds are generated annually.
Although some of this waste finds commercial use as fertiliser on farms, most is destined for landfills.
The team suggest that because filter and espresso coffeemakers are more common in homes and commercial kitchens, many of this waste could be put to use as a valuable source of antioxidants and other useful substances such as caffeine.
Even after these compounds are extracted, they note that the remaining grounds can still be used for fertiliser.
Source: Journal of Agricultural and Food Chemistry
Volume 60, Issue 51, Pages 12565–12573, doi: 10.1021/jf3040594
“Evaluation of Spent Coffee Obtained from the Most Common Coffeemakers as a Source of Hydrophilic Bioactive Compounds”
Authors: Jimena Bravo, Isabel Juániz, Carmen Monente, Bettina Caemmerer, et al