This would be pretty easy to do, I think. Make a subclass of HealthPotion in gamesys and change its ObjectMesh to whatever food mesh you want to use. Then copy the HealthPotion script and change the parameters to appropriate values, like a lower healing value and a different sound. Put the new script in place of the HealthPotion script on your new gamesys archetype. Then edit the Inventory section in the properties to whatever you want, at least the InvName property so it doesn't say it's a health potion in your inventory. I think it would work after that.
If you want go a more simple route with only scripting changes then just change the script condition to "When I am frobbed by player" and add an action at the end "Delete linked objects [MYSELF]" This will automatically eat the food when it is frobbed in the map.