One sign of change in Iran as it works toward a nuclear deal with world powers is the way it is feeding itself, with private grain firms beginning a slow return to their traditional role as major food commodity importers. Iran was never barred from buying food under sanctions imposed by the United States and the European Union over Tehran's nuclear activities. But the measures have made trade more difficult for the past two years by hindering payments and ocean shipping, which has left the bulk of the work in the hands of state buyers such as the GTC and SLAL. However, Tehran has won limited relief from the sanctions after agreeing to curtail its nuclear activities…