More than Mom's apple pie, peanut butter is the all-American food. With its rich, roasted-peanut aroma and flavor; caramel hue; and gooey, consoling texture, peanut butter is an enduring favorite, found in the pantries of at least 75 percent of American kitchens. Americans eat more than a billion pounds a year. According to the Southern Peanut Growers, a trade group, that's enough to coat the floor of the Grand Canyon (although the association doesn't...