If you can believe headlines these days, vanilla is nearly as expensive as silver. A cyclone in Madagascar last year put vanilla bean on the “endangered spices” list. Maybe we should now include vanilla extract in our homeowners’ policies. But all is not lost. For those of us who swirl spoonfuls into our yogurt and pour it into our baking, there’s no need to cut back. It’s “vanillin,” the active flavor ingredient in vanilla, that we really love. “Vanilla extract” has other chemicals, too, but they have negligible taste and degrade when heated. We’re in it for the vanillin. And we can get it in “imitation vanilla.” But why, Mr. Science, should we settle…