Edible memory

Each week during the growing season, farmers' markets offer up such delicious treasures as brandywine tomatoes, cosmic purple carrots, pink pearl apples, and chioggia beets -- varieties of fruits and vegetables that are prized by home chefs and carefully stewarded by farmers from year to year. These are the heirlooms and the antiques of the food world. While cooking techniques and flavor fads change from generation to generation, a Ribston Pippin apple today can taste just as flavorful as it did in the eighteenth century. But how does an apple become an antique and a tomato an heirloom?…