When he was a college student, Pierpaolo Polzonetti was hired by an opera-loving cookbook author to research composer Giuseppe Verdi’s favorite recipes. There weren’t any, but it led Polzonetti to a fascination with what he dubs “gastronomic signs” in opera. Many years later, the result is the recently published book Feasting and Fasting in Opera: From Renaissance Banquets to the Callas Diet by Polzonetti, the Jan and Beta Popper Professor of Music at UC Davis.