Proper storage of coffee grounds and coffee beans maximizes taste. Moisture, oxygen, and light degrade the flavor of coffee; this process starts in the roasting and continues through grinding, a period when the cells open up and absorb the moisture present in air. Because light generates heat that evaporates the essential oils, to maximize flavor, coffee is stored in a cool dark place. For the same reason, coffee purchased in a paper bag turns stale faster than coffee sold in a can.
Coffee purchased in a can is "vacuum-sealed" or "vacuum-packed" in a process that removes approximately 90 percent of the air. An unopened can of vacuum-packed coffee stays fresh for months, but once the can is opened, the grind is exposed to oxygen and turns stale in 7 to 10 days. To prolong freshness, transfer coffee packaged in a bag or a can to an opaque glass container made with an airtight seal and store it in a refrigerator or freezer.
Coffee grounds stay fresh in a refrigerator for approximately 7 to 10 days and in a freezer for about a month. However, the daily removal of grounds from the freezer permits moisture to collect inside the container. When the container is returned to the freezer, the moisture inside the jar condenses and destroys the potential flavor of the brew.
The best brew is made from freshly roasted coffee beans selected from a closed bin rather than an open burlap bag, specifically beans bought from a store that does a high-volume trade in coffee. After purchase, divide the beans into smaller quantities, such as half-pound portions, and store the beans in the refrigerator or freezer in an opaque airtight container. Whole beans stay fresh in a refrigerator for about 4 weeks, in a freezer up to 6 months, and at room temperature up to 10 days.
Because coffee beans are porous, store them away from odoriferous foods, such as cheese, onions, and fish. Roasted coffee beans do not freeze and can be ground immediately upon removal from the freezer.