Microorganism

The earthy smell after rain has a name: Petrichor. Its core is Geosmin, a molecule from soil Microorganisms that the human nose catches at just 5 parts per trillion—said to beat a shark smelling blood in water. Perhaps a trace of ancestors who sniffed out water on dry land.

Seasonings slow food spoilage not by killing microorganisms, but by stealing their water. Salt and spice molecules bind with free water in food, lowering its 'water activity.' Even if water is present, microbes cannot use it.