Coffee Storage...Air Tight or Leave the Lid Off?

Published in BCE Issue No. 2, June 2, 2000

Coffee and Roasting Research by Ken Mary

I will now present a controversial theory regarding the "resting" of coffee after roasting. I made a series of 3 roasts in which half of each was stored in a closed but not airtight jar, and half put out in a shallow dish on the kitchen windowsill. My initial intent was to characterize spoiled coffee due to deliberate exposure to air and light, and compare with properly stored coffee over several days. This was to be in preparation for a more extensive test, and the limits had to be determined.

I made no attempt at a proper cupping but instead prepared coffee in my french press or cafetiere as usual and took notes on fragrance, aroma, and flavors of the brew (cup profile) as it cooled during normal consumption. There were 2 different coffees and one was roasted to 2 different levels, city and full city. Two brews, one from the jar and one from the exposed coffee were made daily for 3 days for each roast. All 3 roasts yielded the exact same totally unexpected results. The coffee "properly" stored in a closed jar had no significant change in cup profile. After 3 full days, the jar coffee was either slightly better or slightly worse than the brew made immediately after the roast.

HOWEVER, the exposed coffee IMPROVED daily and in my opinion, the cup profile was better in every description even (and especially) after a full 3 days exposure. There appeared to be an evolution or development of certain chocolate-like flavors, and an increase in the duration and sweetness of the aftertaste.

My theory is that coffee must be deliberately exposed to the open air for some period of time so that desirable flavors can develop. This exposure may enable the very element most want to avoid, Oxygen, to combine with precursors to form the flavor chemicals. Some of you may say that I have been drinking bad (not home roasted) coffee for so many years that I prefer the taste of spoiled coffee. Let me say that I am all too familiar with rancid, spoiled, burnt, store bought coffee, and I can tell the difference between that and properly developed home roasted.

The experiment is simple and I encourage all readers to try it for yourselves. Since the experiment was completed a few months ago, I have stored all of my roasted coffee in jars without lids. I am continually impressed with the improvement in flavor with time.