James Hoffmann is the 2007 World Barista Champion and co-founder of London’s Square Mile Coffee Roasters. He is also the owner of a rather popular coffee-based YouTube channel (he’s closing in on 90,000 subscribers), where he offers tips, tricks, and reviews for those looking to increase their coffee knowledge. Hoffmann is a big name in the industry, and when he says you should be doing something to improve your brew, people listen. But in his latest video, Hoffmann suggests you microwave your coffee beans, and we’re like whaaaaaaaaaaat?
But as odd as it may sound, there may be something to it.
In the video, the second in his Weird Coffee Science series, Hoffmann builds off something he noticed in the first installment: that brew temperature affects flow rate of a v60 pour-over. To test heat’s effect on espresso, Hoffmann dialed in a shot using room temperature beans and then pulled a second shot using beans heated in the microwave to around 60°C (140°F). He found that the second, heated shot pulled significantly faster, further lending credence to the results from the first video.
The question then arises: is it heating the coffee before grinding that has the effect or is it more of a function of just the puck itself being hotter. To find out, Hoffmann then grinds room temperature beans and microwaves them to 60°C. That shot pulled at a normal length. From there, the conclusion is drawn that the hotter beans actually grind differently than their room temperature counterparts.
But which one actually tastes better? That is, after all, the whole point, right, getting a better product and not just making things behave differently by doing weird stuff to them. For this, Hoffmann dialed in shots for both room temperature and nuked beans. Both coffees were then ground simultaneously and allowed to sit so their temperatures could equalize (thus removing the variable of puck temperature). To keep from knowing which beans made which espresso, Hoffmann had Square Mile coworker Gareth Jones pull the shots. In this side-by-side comparison, Hoffmann states that he “did prefer the shots that were from the hotter coffee beans,” most notably because of the texture, which he describes as, “richer, softer, [and] rounder.”
The reasons for this phenomenon Hoffmann isn’t quite sure of. He offers up the possibility that the heated beans could have increased the overall extraction percentage. Some commenters have proffered the idea that heating the beans changes the moisture in a bean—some say by spreading it throughout the bean, some by removing it—and that is what is causing them to grind differently.
But whatever the science behind it, heating your coffee beans before you grind them will make you coffee taste… better? If it’s good enough for Hoffmann, it’s good enough for me. But if you’re more of the skeptical sort, Hoffmann gives you all the information you need to repeat the test at home. Test it for yourself and post the results on his website here.