Stepping outside after this weekend’s much-needed downpours, I was met with a familiar fragrance. The smell of the earth after rain, sometimes called “Petrichor”.
This is a fairly modern word, cobbled together by a couple of scientists in 1965.
It’s derived from two Greek word roots. Petra (πετρα) meaning “rock” and ichor (ιχωρ) meaning “blood”. But ichor is usually a special sort of blood – the juice that flows in the veins of a god or giant, perhaps a monster, not a mere mortal.
Petrichor’s scent is strongest after rain beats down on hot, dry soil. When rain pummels the earth, it stirs up waste from tiny soil bacteria called Actinomycetes… tossing tiny particles of something chemists have named “geosmin” into the air.
Interestingly enough, this same compound that brings us that lovely post-rainstorm aroma is also responsible for strong earthy flavors.
It’s why catfish and other bottom-feeders can taste a bit muddy at times (especially when caught in hot weather). It’s also why fungi and vegetables can taste a bit earthy, even after being thoroughly washed. Personally, I’m fond of strong-flavored catfish and earthy beets and mushrooms, but to each their own.
If you’re not fond of those earthy flavors, consider adding an acid during cooking (such as vinegar). This will cause geosmin to break down and give you less-fishy tasting fish or vegetables that taste less of dirt.
On a more entomological note, mosquitoes are attracted to geosmin’s smell in preparation for laying their eggs. A number of entomologists and chemists are currently experimenting on traps using geosmin extracted from beetroot skins.
I look forward to seeing how geosmin trap technology develops – but I suspect it’d be quite possible to come up with a homemade trap based on the same principles that’d work well. After all, if we can collect and destroy many mosquito eggs, we should see some dint in next years’ mosquito populations.