Today home roasting is becoming popular again. Computerized drum roasters are available which simplify home roasting, and some home roasters simply roast in an oven or in air popcorn poppers. Once roasted, coffee loses its flavor quickly. Although some prefer to wait 24 hours after roasting to brew the first cup, all agree that it begins to get off-flavors and bitterness about 1-2 weeks after roasting even under ideal conditions like being stored in an airtight container or de-gassing valve bag.

Depending on the origin and storage technique coffee flavor can peak anywhere after 24 hours with some coffees reaching peak flavour after 14 days. After this period of improvement coffee flavor declines, once again factors such as origin and storage influence the speed of this process. Grinding roast beans accelerates the rate of staling to a matter of minutes. There are numerous factors involved in the decline of coffee flavor after roasting, among these are the oxidation of oils and other compounds exposed to atmospheric oxygen after the roasting process damages bean cell wall integrity, and also the loss of flavor active volatile compounds to evaporation. It is worth noting that freshly roast coffee beans produce a significant amount of carbon dioxide (CO₂) gas as a result of the roasting process. This CO₂ gas has a modestly protective effect for freshness to the extent that it prevents atmospheric oxygen from contacting the beans. Other means of extending freshness such as freezing roast beans and displacing surrounding air with an inert gas are somewhat controversial.

Because home roasters have control of the roasting quantity and schedule, they can arrange to have coffee available at or near its flavor optimum. Many home roasters insist on roasting several times per week for the sake of obtaining optimal coffee flavor.

Unroasted (green) coffee beans can have a shelf life of one year or longer if properly stored.

Information Source: Wikipedia and Image Source: Wikipedia

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