Avodah Zarah 67 - Forbidden Flavor that Ruins the Dish

Whenever a forbidden substance gets mixed into a kosher dish and it improves the taste of the dish, the result is prohibited; however, when it has an adverse effect on the permitted food, the dish is permitted. The forbidden substance should not be found in large quantities, so that by eating his meal within a short time (about 2-3 minutes), one does not ingest more than an olive volume of the forbidden food. Also, if the prohibited food, when added to a cold dish, improves it, and adds the bad taste only after cooking, the permit does not apply.

A forbidden food that is absorbed into the walls of a cooking utensil becomes slightly rancid after a day. Since it adds bad flavor to anything cooked in this utensil, it follows that kosher food cooked in it does not become prohibited - this is the opinion of Rabbi Shimon. Rabbi Meir, however, says that even when the forbidden flavor is detrimental, it still prohibits the dish.

Art: Cornelis Jacobsz Delff - Still Life with Kitchen Utensils