|How to Keep Roasted Coffee Fresh|
© 2007 The George Howell Coffee Company
Most of what follows is a combination of both common sense, and that information as learned from the food industry in general. These observations will likely change over time, but are representative of current best practices as we know them today. Please feel free to write us with your comments and suggestions, as we are always interested in learning something new!
Material sciences are responsible for miraculous improvements in technologies, including packaging of foods. We use what we believe to be state of the art packaging. We use 4.5-mil aluminized-mylar bags, with one-way valves (allowing CO2 out, but no air in). Used properly, this packaging will keep roasted whole bean coffee fresh far longer than previous incarnations of packaging for coffee, whether they be waxed, foil or plasticized paper, metal cans, or plastic bags.
Process we use at Terroir Coffee
Within a few hours of roasting, the roaster will evacuate the bag of all air (containing oxygen), and flush it with inert gas such as nitrogen (to fill the voids that used to be taken up by air), and then thermally seal the bag. This is all done on a single, specialized food processing machine. An important detail is the addition of a one-way valve to let CO2, a natural by-product of fresh roasted coffee, to continue to escape, but not let air back into the bag. Without this valve, the bags will inflate hard as CO2 builds up considerable pressure, but cannot escape. CO2 emission is a sign of relative freshness, and can also be seen as it creates a brown froth during brewing. Why nitrogen? Have you ever gone to the farm stand for apples late in the fall, long after your apples at home are starting to get soft and mealy to find fresh, crisp tasting apples from the farm stand? Those apples were harvested at the same time as the ones in your fridge - nitrogen environment cold storage.
These sealed bags can be stored at normal room temperatures, or in a freezer. One interesting issue here is that with time, the CO2 will displace some of the nitrogen. Without getting too deep into the chemistry, it is the initial oxygen we are interested in removing, to preserve freshness. The CO2 also serves to displace the oxygen in this application. Nitrogen is widely used because it both displaces oxygen as well as inhibits the growth of fungus or bacteria, neither of which are a problem for roasted coffee. Displacing oxygen, however, seems to be a universally recognized benefit [for longer term coffee storage]. We have taste-tested our coffees packaged this way at 1-week increments stored at room temperature and found them to remain fresh tasting for many weeks, with little discernable difference from the same coffee roasted fresh to the same profile.
What we Recommend for Storage
Coffee packaged in one-way valve bags as we have described can be stored in a cool dry place, or stored in a freezer.
Once the bag has been opened, the remaining whole bean coffee can be stored until used up in any of the following ways:
We do not recommend storing beans in an air-tight container under any circumstances, as it virtually guarantees that air from the room is not removed nor displaced from the storage medium, allowing plenty of oxygen to accelerate the staling process. Further, it does not provide for venting the CO2, so pressure will build up inside the jar.
It is also recommended not to re-freeze, or cycle the beans back and forth from the freezer to room temperature. This temperature cycling will also break down the beans, and accelerate aging.
Storing pre-ground coffee greatly accelerates the staling process, because the entire surface area of the bean's cellular structure is now exposed to oxygen. So, always, always (did we say ALWAYS) grind just before brewing. Some studies have found shelf life of less than one (1) hour when ground coffee is placed into an airpot, or filter, and left for hours before brewing. Best to throw it into the compost, and start anew.