I once wrote a column called “Grapefruit is the New Umami” because it’s a leap for cocktail students to grasp. In cocktails, grapefruit juice plays a chemistry role that has nothing to do with the horrid half-grapefruits your mother made you eat, or someone’s lamebrained crash diet. The Grapefruit juice (fresh, SVP) or bitters, “brings the whole room together” as Mr. Lebowski once said. You don’t taste the fruit per se, you taste an experience that couldn’t come together without this dear ingredient. Try it. Not Greyhounds, although those are fine— something more complicated.