Brewing Frozen Coffee

A few months back, James Hoffman was written up in the New York Times. I'd sort of lost track of James - back when I had my roasting business he won his WBC chapionship, and later had his incredibly popular blog jimseven. That's nothing compared to now though, he's apparently turned into a full-blown coffee celibrity with crazy lots of subscribers on his YouTube Channel.

So, I had to see some of what he was up to, and about the same time as the article, he had a video about freezing roasted coffee beans, a subject I was really into in the mid 2000's. We roasted on a Sivetz electric, and Mike Sivetz was doing research into what happend when you freeze roasted coffee and has some patents on various techniques. By the way, Mike's patents are fantastic, they're worth looking up and reading, an amazing amout of knowledge packed into them, as with everything Mike did.

I did a bunch of experimentation back then and came to the conclusion that if you're using coffee immediately, don't freeze it, but sometime between day 7-10 the staling of unroasted beans beats out any degredation from the freezing and the frozen beans taste better. This was after taking some coffee immediately out of the roaster, freezing some and then doing daily cuppings of frozen vs unfrozen.

Back to James and his video, he has so much fun with it all, not only reviewing the findings from a published paper, but then replicating the experiments in the paper. With LIQUID NITROGEN!???! Yes, liquid nitrogen and all, so awesome. And an EK-43 grinder.

Full disclosure: I've never had the opportunity to do coffee experiments with liquid nitrogen, and that's a serious oversight on my part.

Anyway, I was watching James' video and was just enjoying the ride, when he came to something that didn't ring true to my memory of my older experiments: the conclusion that there was no difference between taking frozen beans and grinding immediately and letting them thaw some. That it didn't effect the extraction one way or the other, and that moreover, the particle uniformity was better if you grind immediately without thawing.

My memory was that grinding frozen beans resulted in less extraction than thawed. Time to put it to the test again. A Vario grinder, a couple of Obrew's and mason jars, a scale and some coffee:

The result? My memory is right, it's underextracted right out of the freezer. Whew, decades of thawing and waiting a couple of minutes before grinding were not in vain.

So, why different than James' result and the published paper? It has to be the freezer and the grinder. A residental freezer is a lot different than liquid Nitrogen. And a Vario grinder, while great, isn't an EK43.

My proposed amended conclusion: if you're a mere mortal and don't have some liquid Nitrogen and a high end commercial EK43 grinder handy, then you might consider thawing before grinding.

Just to clarify: I'm not saying anything about particle uniformity or the taste of grinding immediately vs letting it thaw. My tests don't speak to either of those, just to the extraction of thawed vs frozen.

A big thanks to James for prodding me to redo my mid 2000's experiments, so enjoyable to revisit it all.