פירוש על עבודה זרה 74:16

If any food that non-Jews change from its original form is prohibited, then if they roast ears of wheat they should be prohibited. But they are not.

The Talmud now refines the comparison with water. Water retains its natural form and so does wheat that has just been roasted. It still looks like wheat. The cooked food would become prohibited only if it has really been modified.