How to Store Ground Coffee

While I generally recommend buying whole bean coffee and grinding it just before brewing, I recognize that many people like convenience of having the coffee preground and ready to go if they want a quick cup. If that's your situation, here's how to store coffee grounds to maintain the maximum flavor.

As you remember from the description of the roasting process, heating green coffee beans drives out moisture and develops volatile oils in the beans, the so-called coffee essence. It's this coffee essence that we want to preserve when we store coffee grounds.

There are two main factors that destroy the essence. One is that they simply evaporate into the atmosphere. The other is combining with oxygen in the process of oxidation.

That automatically implies part of the solution: minimizing exposure the coffee grounds to air. This is why most coffee you see at the grocery store comes in vacuum sealed cans or bags.

Once the vacuum seal is broken the speed of degradation of the coffee speeds up. You can minimize it by keeping the coffee in a tightly sealed container. There some containers on the market that that you use a hand pump to evacuate air and help minimize oxidation. A simpler method is to keep the coffee in a Ziploc bag and press all the air out of it. Because exposure to heat and light speeds up oxidation, it's good to keep the bag stored in a dark, cool spot.

The question I wanted to answer to my own satisfaction was whether or not storing coffee in the freezer made in those with different. Here's what I did to find out.

I bought a bag of pre-ground, dark roast Starbucks coffee at the grocery store. When I got home, I poured it into two Ziploc freezer bags, squeeze on the air out and sealed them. One went into a canister on the countertop and the other into the freezer. I used a single cup drip coffee filter to make a cup of coffee from each bag at different intervals. Here are my personal results. Feel free to run the test for yourself.

At one week, I couldn't really tell the difference. Maybe real coffee connoisseur could, but I didn't. However, by one month I thought the room temperature coffee was distinctly flat compared to the coffee made from ground that had been stored in the freezer.

One other thing I noticed during testing is that letting the ground from the freezer warm up some before brewing made a difference. This makes sense since warmer oils would be easier to extract. This is probably especially true for brewing a cup at a time. I'm not sure if it would make as much difference for whole pot or not.

So here's the bottom line. If you using your preground coffee up within a week or so, it's probably okay to keep it in a tightly sealed bag in the dark at room temperature. If you're storing it for longer periods of time you should probably keep it in the freezer and let the ground you're going to use come to room temperature before you start brewing.


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