Do Used Coffee Grounds Really Absorb Odors? (Hint: The Answer is No.)
I used to love the fact that used coffee grounds could be used to absorb odors. (I’m even working on trying this out outside of the fridge.) My mom used to do this, storing them in a plastic tub and putting them in the back of the fridge. Since then, I’ve done this quite often, but remain skeptical as to its actual effectiveness.
My question is *how* or *why* would used coffee grounds absorb odors? One theory might be that they absorb moisture—but these coffee grounds are pretty hard and they “breathe” in and out water through boiling and brewing, not just through sitting in open air. Another might be that the acid in the beans might neutralize odor-causing proteins in the air. (I think I just made that up right now.) (Apparently, alkaline products can neutralize acidic odors in the air—an attribute and function that apparently even baking soda is no good at.)
The theory I think is most plausible (which is also my own) is that the faint hint of coffee smell lingering about the grounds covers up other smells in a fridge or anywhere else.
It seems that most odors are removed by (1) killing the bacteria that causes them by washing or disinfecting, (2) using enzymes to remove organic material, (3) absorbing moisture and killing bacteria by drying them out, (4) covering up the smell with another more pleasing smell, or (5) using something like Febreeze which works by absorbing odor-causing bacteria and then binds with them inhibiting them from evaporating their smell into the air. It seems to me that coffee grounds do none of these except possibly absorbing excess moisture in the air and covering up bad smells. It doesn’t kill bacteria (unless you use it as an abrasive to scrub down your fridge); it doesn’t have enzymes (that I know of) to apply directly to odor-causing baddies; and it doesn’t bind with the baddies to strangle them to death.
The coffee has to absorb *most* of the moisture in the constantly recycling air in the fridge (recycled through each opening and closing of the door), which I doubt it has the power to do. That’s why I think it’s just a mild, pleasing cover-up and nothing more. Which is OK because it’s free, re-using waste, and natural. But just be aware that it’s not the godsend people think it is.