An unopened can of illy ground coffee will remain fresh for at least two years due to illy's proprietary patented pressurized system that extracts air from the can and replaces it with inert gasses at a higher-than-atmospheric level of pressure. This method guarantees a longer preservation time, maintaining flavor and aroma for over 24 months. At the same time it 'ages' the coffee, improving its aroma over time by causing its volatile aroma compounds to bind with the oils that are contained in the beans. Simple vacuum packing cannot achieve this flavor transformation. The positive pressure exerted by illy's method actually forces these aroma compounds back into the coffee whereas vacuum packing lets them seep out. The effect of illy's aging process is similar in many ways to the development of complex flavors when a fine red wine is aged under proper conditions.