THE FLAVOR CALLED PUMPKIN is surging toward a record season in processed foods, with Mars introducing Pumpkin M&Ms, Planters dusting “pumpkin spice” on its almonds and Starbucks bringing back its annual Pumpkin Latte. Sales of last year’s pumpkin offerings climbed nearly 20 percent to more than $290 million, Nielsen reports, and people in the flavor business say the trend has a powerful demographic wind at its back: strong popularity among millennials.

I visited a supplier to food manufacturers, Flavor & Fragrance Specialties in Mahwah, N.J., where Dianne Sansone, the director of technical services, showed me through the laboratory, whipped up some concoctions to taste and pulled back the curtain on what is arguably one of the most mysterious, and misunderstood, flavors in processed foods.