An advisory bulletin released by the Alcoholic Beverages Division in Iowa says that no beverage with a pH level below 6.0 (such as vinegar, fruit juice, or wine) is to be served in a copper mug. This includes the popular cocktail the Moscow mule, which traditionally mixes vodka, lime juice, and ginger beer. Complete with a lime garnish, the drink serves up aesthetically pleasing photo-ops for outlets like Instagram. But the Moscow mule’s pH level is well below 6.0, according to the bulletin.
High concentrations of copper are poisonous and have caused foodborne illness. When copper and copper alloy surfaces contact an acidic food (or in this case, beverage), the mineral can be absorbed into that food. However, copper mugs with a nickel or stainless steel interior lining are safe.
Don't want to take a chance on a Moscow mule? Try one of these easy summertime cocktails, perfect for your August cookout.