https://www.cnet.com/news/impossible-burgers-key-ingredient-wins-fda-approval/ > The key ingredient in Impossible Burger, the meatless burger that bleeds and browns when cooked, has finally passed muster with federal regulators. > Impossible Foods, the Redwood City, California-based startup behind the plant-based burger, said Monday the key ingredient in the burger had been determined as safe to eat by the US Food and Drug Administration. That ingredient -- soy leghemoglobin, or "heme," --  had reportedly been under review by the FDA as a potential allergen.