If Terumah is cooked with Chulin, it must be given to a Kohen to taste in order to determine if the Terumah imparted taste to the Chulin.
The only difference between Chullin and Terumah is in their kedushah status, not in their physical taste, how would any Kohen be able to differentiate by taste, if there is no difference?
ben saketkhou, Boca Raton, USA
The Gemara must be dealing with when the Terumah food is different than the Chulin food, and when mixed we need to determine whether the taste of Terumah is discernible in the mixture.
All the best,
Reuven Weiner