פירוש על חולין 215:6

Rav said - This is because we learned in the Mishnah "if a drop of milk falls on a slice of meat and imparts a flavor to it" it invalidates the whole pot, since that piece itself becomes entirely prohibited and prohibits the other pieces. Even if they consist of [enough volume] to nullify [the drop], they are all prohibited.

Because they are the same type of substance - Rav holds like Rabbi Yehuda who said that min b'mino does not nullify.