No matter how (and if) the food system is revamped to cover how much food is produced based on the source, there have never been any discussions regarding separating the end product into different types of food. So you won't be able to trade 100 bushels of grain and 300 pounds of fish. You will still just have "400 bushels of food".
However, additional trade goods are on the radar, including wood, stone, metal, and manufactured goods.
