Traditionally, flavor has been discussed in the food world as a two-dimensional component — aroma and taste. With a biochemistry and public policy background, Nik Sharma has studied how people respond to different things but also how ingredients respond to us. He parses the anatomy of flavor in tastes such as fieriness, the risk-reward factor of tolerating hot foods, and how the brightness of acidic foods like limes and sumac can build taste and texture. Sharma’s new book is “ The Flavor Equation .”