You soak a batch of dried beans overnight, simmer them for hours, and still find a stubborn, slightly chalky center. It is tempting to blame the soaking time, the burner, or the recipe. Sometimes, however, the beans have developed a real storage defect known as hard-to-cook, or HTC.

HTC is not simply a case of beans being extra dry. During long storage—especially in warm, humid conditions—the chemistry holding their cells together changes. Water may enter the seed perfectly well, yet heat has trouble dismantling the structural “glue” inside it. That distinction explains why another six hours of soaking can accomplish surprisingly little.