It’s All About Congeners
All alcohol is dehydrating, which means all of it can cause hangovers. But hangovers do range in severity depending on the type of alcohol, thanks to congeners, which are byproducts of fermentation. These contribute to a drink’s flavor and color, but are very difficult for the liver to break down, and cause hangover symptoms like headaches.
“Yeast produces these chemicals during fermentation, and a brewer or winemaker doesn’t have a lot of control over the amounts of them, which is why beer has very little amounts,” says Dr. Andrew Waterhouse, an enology professor and wine chemist at the University of California, Davis. “But distillers do have a lot of control—they can either exclude congeners totally or include them to affect the flavor, color and aroma of the spirit, and that’s part of the craft.”
Distillers achieve this by managing the heat in the still, causing some congeners to evaporate and others to stay depending on the temperature level, or by distilling the liquor multiple times, filtering out congeners. This is why, for instance, Irish whiskey distilled three times may taste lighter than double distilled Scotch whisky.
Some congeners are pleasant tasting and others taste foul, so the distiller has to control what gets removed and what stays in the bottle. Vodka and gin are distilled to remove all of the congeners entirely to yield a neutral flavor, whereas congeners are purposely left in darker spirits to add depth of flavor and dark color.
“Brandy has the highest amount, followed by dark alcohols like whiskey and red wine,” says Czarena Crofcheck, Ph.D, a food science professor at the University of Kentucky. “Their high levels of fusel alcohol make them much harder for the body to metabolize.”