The odour of a selection of cheeses in our fridge was so overpowering that I looked online for a solution. As suggested, I left a small plate of ground coffee in the fridge. It worked like magic, absorbing all the odours in a matter of hours. How does this work?
鈥� Live cheeses are complex bacterial cultures. Cheese acquires flavour as the bacteria 鈥渞ipen鈥� it by digesting the proteins, fats and sugars in the original milk. This produces many small volatile organic molecules, which constitute the aroma.
Coffee beans are oily, as anyone failing to clean their espresso machine soon discovers. Ground coffee is coated in coffee oil and since this is chemically related to the organic aroma compounds released from the cheese, it is relatively easy for them to dissolve in the coffee oil.
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What is more, the surface area of a small quantity of finely ground coffee is probably greater than that of the fridge and all its contents. This creates a large adsorbent surface for the cheese aroma molecules. I have used baking powder to remove odours in the same way.
Simon Goodman, Griesheim, Germany
鈥� Cheese contains naturally occurring chemicals called free fatty acids, such as butanoic and octanoic acids. These contribute to its flavour and aroma, but can become overpowering. Coffee grounds have a large, porous surface area and the cheese odour molecules get trapped in the pores and held there via weak van der Waals forces. This stops them reaching olfactory receptors in our noses, preventing the smell. Activated charcoal works via the same principle and is common in water purification and industrial gas processing.
It is also possible that some compounds in the coffee, such as furan-2-ylmethanethiol (roasted aroma), bind preferentially to olfactory receptors, effectively masking the smell of cheese by introducing another smell.
Vanessa Ip, Hong Kong, China
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