Green Coffee Storage
People in the coffee trade used to say that raw coffee was eternal and we used to say that too. The revised estimate is that green coffee lasts a year from processing- counting on a six-month rotation of stock. We are unlike most green coffee sellers in that we do not have old stock - we are careful that the coffee you receive is not more than three months to nine months old. This can mean that certain origins are unavailable for certain times of the year. If we sell out of the last crop year (something we always want to do) and new crop has not come in, that means we will not have that coffee until the new season. It is helpful to think of coffee as produce with a seasonal cycle, just like apples, peaches or asparagus. Coffee is not nearly as time sensitive as peaches though!
Coffee Storage for Transport
In the past few years, changes have been made in how coffee is handled, changes of which the end user is probably not aware. For a few hundred years, green coffee has been exported in 60 kg or 70 kg (132 to 152 pounds) natural fiber bags, jute, sisal or burlap. Coffee keeps a reasonably long time in these bags (about a year) and they are very durable. In the past few years, however, the specialty coffee industry has been experimenting with alternatives, primarily vacuum packaging in Mylar bags and shipping in cardboard boxes. It is a big investment for mills to install this type of equipment, and to change their handling of green coffee in this way, but the results are clear - vacuum packaging does extend the flavor-life of the coffee.
Vacuum packing at origin is still fairly rare because of the cost. We see it with Cup of Excellence auction coffees, Daterra, Panama Esmeralda, and a few others. It is an expensive process - adding roughly 10 cents a pound. Now .10 a pound might not seem like much to a home roaster; if you use say 50 pounds a year - it is $5. But it adds up when you are buying thousands of pounds. Buyers of top-tier specialty coffee will cope with this increase, but for middle-tier specialty coffee, where cost is more of an issue, I am not sure this technology will be implemented. Vacuum packaging requires a lot more handling too - as the vacuum sealed blocks of coffee seem to work best in the 25 to 50 lb. range - not 132 to 150 lbs. like the bags.
The second part of this issue is what happens when the coffee gets to Sweet Maria's . That's where the Mighty Mutt comes in, our commercial vacuum sealer. As we have been buying more micro-lots, we need to keep these coffees stored in top condition for longer. These coffees are shipped to us in burlap and we have repacked the coffee, either using the Mighty Mutt, or transferring it to GrainPro SuperGrain bags. The GrainPro bags are a multi-layer plastic bag (a vapor barrier sandwiched between two layers of polyethylene) made to prolong the storage life of dried grains and seeds. They provide a moisture and vapor barrier, protecting against "ingress of water vapor, while retaining low O2 and high CO2 levels created by the respiration of the commodity" (quoted from the GrainPro literature). The use of these bags has been suggested for some time, and the results of an interesting study conducted by Andrew Miller and Luke Harris were published in Roast Magazine in the July/August 2008 issue. Their study on four different coffees found that coffee flavor was more well preserved by warehouse storage in GrainPro than in jute. Because of the high cost of the GrainPro bags, some producers and coffee roasters are experimenting with storage in simple 4 mil poly bags, and those results are encouraging.
The benefits are much better from some origins than others. Dry Process coffees should only be packaged this way in special circumstances. GP and Vac Pack can DAMAGE DP coffees, and ones that have not undergone a full rest in parchment (reposo). If the coffee has high water activity, it will harm the cup quality. Anyway, as far as GP we feel they add 3-6 months to the shelf life, conservatively, Vac pack has longer term benefits if they are multi-laminate bags ... 9 months.
In a way we here at Sweet Maria's are attached to the burlap bags- since so many are decorated in a lovely way and they are so authentic, in a way that a Mylar or plastic bag and a cardboard box can not be. We transfer coffee from ship ours in zip lock polybags to ensure cleanliness and keep costs down.
Home Storage
In terms of storage at home, all green coffee beans should be kept cool and dry at room temperature and away from direct sunlight. The refrigerator is too moist for green beans and the freezer is too dry. In the trade, the general rule in terms of climate for green coffee storage is this: if it's comfortable for you, then your coffee is happy too. The best storage conditions for raw coffee probably exist down in your basement, or another part of the house that is not subject to large shifts in temperature and humidity. You can store it in the ziplock bag for about a month, but longer than that use just a fabric or paper bag since it allows better air movement. There are bugs or larvae that might be attracted to the burlap or cotton - but almost nothing will eat green coffee. If the coffee gets wet - you can get mold.
It is not necessary, but if you have a home vacuum sealer you may consider vacuum packaging any lots you want to store a longer time. It will protect the flavors of the bean, especially in humid environments. In our experience, vacuum packaging works best on wet-processed coffees; dry processed coffees seem to do better in jute or burlap storage. Some folks, like specialty coffee pioneer named George Howell is experimenting with deep freezing green coffee but I don't think that is practical.
Coffee stored for 3+ years can be considered aged coffee. Aged coffees are put through a specific process of rotation, not just left to sit in a bag, so all old coffee is not "aged." Aged coffees display unusual (and often desirable) qualities, such as reduced acidity and interesting flavor notes. Not all coffees age well, but some are greatly improved. Particularly bright coffee lose their character after about a year and taste flat - but more earthy coffees can age well, Older coffees usually display a "baggy" quality - they start to taste like the bag they are stored in.
As we have stated elsewhere many times, it seems wrong to create a "coffee cellar" like wine, since it is a perishable crop though the idea of being able to extend the availability of your favorite coffee certainly seems appealing. Our attitude is to treat coffee like produce, to enjoy it while it is fresh and in season. Yet coffee is an agriculture product somewhere between "fresh" and "forever" É and new packaging methods are uncovering ways to maximize cup quality for sustained enjoyment.
For some thoughts on roasted coffee storage and grinding/brewing.
updated 5/09
excellent graffiti from the royal coffee warehouse
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