Coffee Beans - Freshness and Storage
Coffee beans for Italian coffee machines need to be fresh. This doesn’t mean keeping them in bags. Fresh means fresh. Remember, coffee is a fruit and just like with any fruit, fresh is best. However, after roasting all beans need a short period for degassing. Here is a guide to when coffee beans are generally at their best after roasting:
Light roast - 3 - 40 days
Medium roast - 5 - 30 days
Dark roast - 7 - 20 days
It's experience and the palate that tells the whole story but here's the theory to back up the results in the cup. Just as with any fruit exposed to oxygen there's quick degradation through oxidation. When beans are freshly roasted a nice amount of coffee oils are trapped inside the internal structure of the beans. As the beans age the internal structures breaks down and oils are released. These oils make their way to the bean surface and at the surface they oxidise to form a number of rancid compounds.
The oils get released slowly for light roast beans, but then quicker and quicker as beans are roasted darker. Have you been to a coffee shop and seen shiny oily beans in the hopper? If the oil is on dark roast beans that's OK, but if the oil is on light roast beans that's a really bad sign.
As mentioned above, oxygen is the enemy. A bag with a one way gas valve can help keep beans a little longer as after roasting beans they off-gas and these off-gases push the damaging oxygen out of the bag.
Here's something that's a surprise to many. Once you open that bag with the one way gas valve there is no point at all in re-sealing it. It's a very common misconception that re-sealing beans will protect them but this isn't the case as when you re-seal the bag there is none of the original off-gassing to push out oxygen. This means that the beans are now sitting in a bag that's full of oxygen.
My advice is to keep bags sealed until you need the beans, then to tip the lot into your hopper. The beans will last just as long this way with the bonus of looking good in the hopper.