Ted cites studies that show that after a certain period of time in refrigeration, a phenomenon called internal breakdown occurs in peaches. They get dry and mealy, or hard and leathery, or they can brown on the inside. read more
Many fruits turn brown on the inside. After cutting a process called oxidization starts to discolor exposed fruit flesh. It’s just a color change and does not effect any other aspect of the fruit. Its also a sign of age. When peaches are ripe they can turn brown from the pit out. read more