Carbon dioxide has its own flavor, which affects the overall taste of a drink. (At high partial pressures—which is to say, when a gas contains lots of CO2 relative to other gases—it also sets off the body’s pain receptors, called “nociceptors.” One trick almost every distiller I visited tried to play on me was to get me to stick my head into the vat during the final stages of fermentation, when the headspace—the volume of air above the liquid—is a cloud of CO2. Taking a whiff is like sticking a knitting needle up your nose. Too much of it, and you can pass out and fall right into the vat.
