难以食用 also implies the object cannot be eaten or it is almost impossible to eat it (e.g. 难以抵挡 = cannot withstand; 难以置信 = unbelievable)
无从下口 also refers to 'can't interject opinion'
I suggest 食用不便 (inconvenient to eat) or 吃来麻烦 (trouble to eat)
For example, crustaceans with hard shells, fish with fine bones are inconvenient to eat, but not impossible