"Staling is defined as the loss and alteration in composition of the volatile aroma constituents"
(Sivetz, Coffee Technology 1979)
There are three basic components affecting the flavor of air-roasted coffee, they are: body, taste, and aroma. Body and taste are relatively stable components since they do not change much over time. Aroma, however, is referred to as a volatile component since it dissipates quickly after roasting.
Of the 1000 or so chemical compounds that make up the flavor of coffee, volatile aroma constituents account for almost 80%. Also present in the roasted bean is a considerable amount of carbon dioxide (CO2), which fills the bean as it swells during the roasting process. Although CO2 does not translate to any specific flavor component there is a correlation between the dissipation of CO2 and the loss of aromatic volatiles. As CO2 leaves the coffee bean, taking aromas along with it, oxygen enters in to fill the empty space. The oxygen reacts with the oils in the bean, turning them rancid.
To put it simply, together CO2 and aromatic volatiles can be referred to as gasses. The gasses are the smell of coffee. And when the gasses go away, the flavor goes with it. Once these gasses dissipate the oils become susceptible to oxygen- creating a rancid flavor. Thus completing the definition of staling: the loss and alteration of flavor.
Gasses expand at higher temperatures and contract at lower temperatures. Lowering the temperature of these gasses slows their rate of dissipation. Studies show that for every decrease in temperature of 10 degrees celsius, the life of the coffee increases by 50%. Most home freezers are capable of temperatures of -10 to 0 degrees fahrenheit, sufficient enough to store coffee beans for several months without degredation.
Freezing is one practice that sets Kaladi Brothers Coffee apart from other roasting companies. We place our beans in the freezer directly after roasting so the staling process does not begin before you, the customer, purchase our coffee.
The graph below depicts the staling rate of roaster fresh coffee. Other variables affecting coffee freshness not depicted on this graph are: the particular blend, the degree of roast, the addition of moisture, the humidity of the storage area, the rate of circulation, the altitude, etc.
Coffee freshness can be broken down into five general categories. Roaster Fresh coffee displays full aromatic intensity. Next is Weak Aroma, as the volatiles lose their flavor intensity. Slightly Stale coffee displays some background rancidity characteristics. Stale coffee has lost most of its original aroma while rancid flavors begin to dominate. Very Stale coffee no longer displays any of its original flavor and is characterized by intense rancidity.
Staling occurs at room temperature regardless of how coffee is packaged; packaging alone cannot preserve freshness. For maximum freshness, store your coffee in the freezer.
To protect your beans from moisture damage in the freezer, it is important to use an air-tight container such as a glass or ceramic jar. Studies show coffee stored this way can last up to a year or more!
You may grind your coffee frozen- direct from the freezer. There is no need to thaw the beans before grinding. A side benefit to this method is less build up on your coffee grinder.