Researchers in Australia have demonstrated a new method for decaffeinating liquid coffee using a specialized membrane, a process that occurs after brewing rather than before roasting. The study, published in the Journal of Membrane Science, details an experimental filter made from graphene oxide that successfully reduced caffeine levels in a coffee solution.
Unlike conventional decaffeination which treats green coffee beans, this post-extraction approach targets caffeine already dissolved in the final beverage. The research team from the University of New South Wales developed a layered graphene oxide membrane, modifying its microscopic channels with calcium ions and sodium alginate. This design was intended to selectively allow smaller caffeine molecules to pass through while retaining larger compounds that contribute to coffee's character.
In laboratory tests using a diluted instant coffee solution, the membrane removed approximately 47% of the caffeine content over a 24-hour period. While the filtered coffee retained measurable amounts of other key compounds, their concentrations were also reduced, and the impact on taste was not evaluated. The authors describe the work as an early-stage proof of concept, noting that significant challenges remain in improving filtration speed, durability, and commercial viability before it can be considered an alternative to established methods.