How to get rid of the moisture in coffee?

Question

As pointed out here, my coffee powder seems to have caught moist. Since it is in a significant quantity and a very nice powder, I don't want to waste it. Is there any solution to this problem? The obvious one that came to my mind was heating it up on a low flame, but I don't know the pros and cons of it. Can someone help me with this?

Answer 1

I'll take it as given that the problem you have comes from moisture in your finely ground coffee. Indeed studies show finely ground coffee, other variables being held constant, has a greater hygroscopic tendancy (absorbing moisture from the surroundings during storage) and a higher angle of repose α:

Angle of repose is useful in order to acquire information regarding solid flowability. According to Shittu & Lawal (2007), during powder reconstitution, water molecules that hydrate the product's surface tend to reduce cohesivity between particles, allowing a rapid water penetration; thus, powders that possess high angles of repose, have higher difficulty to incorporate water. All factors tested (roast level, grind size and storage time), and the interactions between them, significantly influenced the angle of repose (α).

I'll report the experiment that I did with removing moisture from used espresso coffee grounds by repeated microwaving. This is no guarantee that it will resolve the problem reported by the OP, where in an earlier Question South Indian filter not brewing properly it was said:

I don't know why, but suddenly it is taking longer to finish the brew and sometimes (mostly from the second time) the water doesn't even go down. It just stays in the upper part of the instrument.

This method of brewing is unfamiliar to me, and the description "to brew without using the middle small instrument which looks like the one used in a french press" sounds like it is akin to a pour over (the tag drip-brew was used there and here).

The possibility of drying coffee grounds was dismissed in this previous Answer:

I wouldn’t attempt to dry wet grounds - the quality would likely suffer and for brewing they will be made wet again, which would make the drying step moot.

However there is perhaps something about the method of brewing at issue here that avoids these objections. So to proceed with the experiment:

On the left is a frozen portafilter basket with used espresso grounds, which presents something of a maximally moist batch of coffee grounds. I emptied the basket into a spare microwaveable dish (a creme brulee crock).

Setting my 1200W microwave to 30 seconds, I ran it and checked to see how hot or warm the dish and its contents became. In the first run the contents became noticeably steamy, but then heating declined (water is specifically absorbing of the microwave radiation). After a dozen runs the used grounds seemed to be contributing nothing to the warming of the dish (an empty crock by itself gets warmed but not hot in 30 seconds).

To the touch the grounds now feel dry, and as a test I put the dish in the freezer for 30 minutes. This produced no clumping or grounds sticking to the dish. So I'm going to say this was a quick and effective technique to dry the grounds per se, without resort to expensive desiccant supplies or DIY vaccum freeze drying equipment.

Finally we invoke the platitude that an ounce of prevention is worth a pound of cure: storing the fresh coffee ground in packaging that prevents moisture absorbtion is easier than trying to fix a problem later on.

Answer 2

If you're looking to get rid of the moisture in your coffee, then you can try one or more of the following methods. The first option is to pour your coffee into a glass jar and store it in a cool, dry place. This will help to reduce the amount of moisture that's present. Another method is to put ground coffee into an airtight container and store it in a sealed bag or container away from light. The high levels of carbon dioxide that are produced during storage will cause the water molecules within the grounds to break down, leading to decreased absorption of water by the beans. Finally, you could also try using an air drier.