The chemistry of cold-brew coffee is so hot right now

Using chemistry to unlock the difference between cold- and hot-brew coffee, courtesy of the American Chemical Society.

Cold-brew coffee is so hot right now, and not just with hipster consumers. Scientists at Thomas Jefferson University in Philadelphia have been taking a deeper look at the underlying chemistry to better understand how the cold-brew method alters coffee's chemical characteristics, with an eye toward pinpointing the best way to cold brew the perfect cup. They had originally planned to present their results last month at the American Chemical Society meeting in Philadelphia, but the COVID-19 pandemic shut that down. So instead, they presented the information in a virtual poster session.

Rather than pouring boiling or near-boiling water over coffee grounds and steeping for a few minutes, the cold-brew method involves mixing coffee grounds with room-temperature water and letting the mixture steep for anywhere from several hours to two days. Then it is strained through a sieve to filter out all the sludge-like solids, followed by filtering. This can be done at home in a Mason jar, or you can get fancy and use a French press or more elaborate Toddy system. It's not necessarily served cold (although it can be)-just brewed cold.

Co-author Niny Rao tasted her first cup of cold-brew coffee a few years ago while attending an ACS conference in San Diego. "I was like, 'Oh, my god, this is great!'" Rao told Ars. "It's not metallic. It's non acidic. It has a little bit of sweetness to it, and it's very full and flavorful."

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