what is that plastic ring/knob in a coffee bag for?
Freshly roasted coffee emits carbon dioxide (CO2) and if the valve is not used, coffee needs up to 24 hours to fully degas before being packaged in a hermetically sealed container. During this degassing process the coffee my be subject to degradation due to oxygen, which quickly makes the coffee go stale. It was Fres-co who invented the degassing valve for coffee, which allowed the packaging of the coffee to be done immediately after roasting to insure the freshest possible taste. The valve allows for the CO2 to exit the package, but will not allow oxygen or other gases back in. Starbucks uses them on all their products, as do almost all coffee packagers. These are bilingual products, one with the valve, one without. Sources: fresco.com; http://www.leaderpackaging.com/news.
