How to Test the Freshness of Roasted Beans
BY Coffee Grail, February 5, 2011
To make sure you are getting the fresh coffee, try the steps below.
1. Grind the roasted coffee beans
2. Place the beans in an open-drop filter
3. Pour freshly boiled hot water over the ground coffee
4. Observe the coffee. If you have stale coffee, the grounds will stay flat during brewing. Fresh coffee will swell or gently rise. This is due to the release of carbon dioxide.
This is caused by the degassing present or absent from coffee. During the roasting process, sugars, proteins, and fats are chemically broken down and release CO2. Because coffee is porous, and because of the pressure inside the bean, the CO2 slowly escapes (degassing) which will leave the coffee inert to boiling water after it has aged. another sign is the presence of oils which will show up on the beans surface after a coffee has sat for some time, reguardless of roast level. (light roasts show oils too). a final test is to throw the bean on the ground, and if it pops and “explodes” it will tell you whether it still has CO2 still trapped in the porous structure.
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