Special to the Coffee Research Department by Anne Kadet 

I’ve always been a coffee bean-grinding skeptic. Do you really need to grind a fresh batch every time you make a new pot? This admonition has always struck me as yet another effort by the global conspiracy of food and beverage snobs to make everything more complicated and effortful. For decades, I’ve been perfectly happy buying bricks of pre-ground Café Bustelo from the supermarket.

But recently, when my friend Per launched his Beim Roaster coffee brand and insisted we brew it with freshly-ground beans for best results, I decided it was time to put this notion to the test.

For the experiment, I grabbed a bag of a locally-produced, whole bean coffee and ground about half the bag using a hand grinder. Then I let the beans sit. And sit. And sit. They sat for four weeks in a jar on the kitchen counter, getting good and stale.

Finally it was time for the test. First, I ground a fresh batch so I’d have just-ground beans to compare with the stale beans ground three weeks ago. What a pain in the ass! For this to be worth it, I swore, the freshly ground coffee would have to be twice as good as the stale coffee.

Next, I gave both batches the sniff test. The freshly ground coffee smelled like, well, delicious coffee! The stale coffee, meanwhile, did not smell good. It smelled a little musty. Like it’d sat in the basement.

I next brewed an eight-ounce cup from each batch, using the pour over method. I was careful to use the same amount of beans and water for each cup. The result: they both looked like coffee!

But the similarity ended there. I first took a sip of the cup brewed with freshly-ground beans. So good! It was smooth, nicely balanced and full-bodied.

Then I took a sip of the cup brewed from the stale beans ground three weeks ago. Whoa. It tasted like the first cup, only with the addition of something off. A dank note, like a flat trombone in a beautiful symphony.

I tried again.

The first cup—very good! Smooth and full-flavored. Delightful!

The second cup— “Horrible!” I couldn’t help exclaiming out loud.

What’s going on? I did a little Google search. Coffee beans oxidize—releasing the gases that contain flavorful compounds. Even when they’re frozen. They can even grow a little rancid.

I am so bummed out. Yes, a cup of coffee made from freshly ground beans is twice as good. It is definitely worth grinding your beans fresh. You win this one, Per.

Happily I did another search and found 14 clever uses for old coffee beans. Skin scrub, anyone?

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