For cats, the main determinant of a food's palatability is its protein content. for cats, then, food tastes especially good when it activates ) receptors in the gustatory system.

Answer: umami

The umami taste receptors are activated by glutamate, which is found in proteins. Umami is one of the five basic tastes that describe food flavor.

Three Umami receptors - T1R1, T1R2 and T1R3 in the gustatory system activates the Umami and sweetness tastes. These receptors get binds to the molecules of food to produce taste. The Umami is the fifth taste apart from the tastes other than bitter, salts, sour and sweetness and its presence is linked to the amino acid i.e glutamate. It is not exact taste but is considered as taste due to its meatiness sensation and due to this reason a cat usually enjoys a non-veg food in the similar manner as the other kind of foods.