We know you care about coffee (that’s why we love working with you!) and we know that you take great care and consider every detail when it comes to sourcing, sampling, profiling, blending, packaging, even brewing and serving. Green-coffee storage is another key area of concern, especially for smaller roasters with limited space and resources, and we know you care about that, too.
If you’re wondering what the ideal conditions are for storing your green, we’ve got a short answer and a long answer for you. The short answer, according to Cafe Imports’ sensory analysis director Ian Fretheim, is: “Cool and dry. That’s really it.”
Of course, there’s never just a short answer. Read on to find out about some specific conditions and containers that might help you preserve the quality and longevity of your favorite lots.
How cool is cool? In Ian’s long-term study of water activity and research into the impact that light, moisture, and temperature have on Aw stability, he discovered that while there’s no universal ideal temperature, “Cave temperature is ideal for some and not for others, but it’s the closest fit for most.” (You can read that water-activity study more in-depth on the Sensory Analysis page of our website.)
At our warehouse, “cave temperature” hovers between 60–70°F. It’s also important that the environment doesn’t experience wide swings, such as extremely hot days and cold overnights, or that your coffee is stored in a direct-sun spot. That being said, says Ian, “everyone’s always going to be limited by what they have available. I’ve certainly walked into cafés where the green coffee bag was leaning up against the roaster. I would probably shy away from doing that.”
Coffee constantly changes and adapts in pursuit of environmental equilibrium: If it has a higher moisture content than the air around it, for example, it will begin to microscopically secrete moisture out into the environment. The inverse is also true: Dryer coffee in wetter environments will absorb some of that excess moisture.
The complicated thing is that coffees from different parts of the world, of different ages, with different processes, of different varieties–basically every variable in the book—will also differ slightly in moisture content and water activity, which will respond accordingly in search of that equilibrium. So… what to do?
“Ok, you’re not going to build a special environmental room for every coffee, so the minimum is based around what seems to be the best overall condition,” Ian says. “That minimum seems to be relatively dry. Around 50–60% humidity seems pretty right on for us in Minnesota: That humidity is lower than the humid parts of the year and higher than the really dry parts of the year, relative to outside temperature.”
Practically speaking, maybe that means keeping your coffee away from doors and windows, steam radiators, dishwashers, dehumidifiers, and anything else that might mess with the moisture in the environment.
“Closing bags is a big one, too, because it blocks moisture” Ian continues. “If you’re in the South and you’re in a humid environment, you can use GrainPro and keep them closed. For most coffee, being in GrainPro is better than not being in GrainPro, but then utilizing that barrier rather than just having it open and sit there. That closed GrainPro bag is a much smaller, easily regulated environment.”
If you’re using plastic pails or tubs like the classic Uline 5-gallon jobs, Ian says, “That’s probably convenient but not great,” depending on whether the lids make a genuine air-tight seal or not. “If your lid isn’t cutting off the connection with the environment, then you’re back in the same boat,” he continues. Short-term storage in the tubs is probably fine for prepping and loading, but for anything else you’re likely better off sticking with the closed-tight GrainPro bag.
You’ve got a small roastery with limited storage and you’re looking around thinking, “It sure gets hot when I’m roasting,” or, “I can’t afford to climate-control my storage but where I live it’s 85% humidity three months a year.” Don’t despair because the conditions aren’t absolutely perfect. After all, nothing in coffee is absolutely perfect.
“If you can do 68°F and 50% humidity that’s wonderful—but if you can’t, then you can’t,” Ian says, reassuringly. “If you have the option of being in one part of the space at 84°F and another part of the space at 78°F, then pick the space that’s 78°F. If you have two spots to use and one is less sunny, I would pick the one that’s less sunny. I would take those combinations of temperature, humidity, and sun, and look for the most moderate combination that you can.”
You can also lean on your importer: Adding a few months of carry to a contract rather than taking delivery of all of your bags at once will preserve them in a climate-controlled space for longer, and can extend the shelf life in addition to saving space around the roastery. (Carry charges are typically between $0.03–$0.05/lb per month.)
Have questions about green-coffee storage? We’re here to help: Feel free to e-mail your sales representative or firstname.lastname@example.org for advice, and visit our Purchase Planning page for more information about buying and working with green coffee.