observation my cat is a picky eater sometimes he would eat all his food sometimes he eats only half of it I do not want to keep spending money on different flavors of cat food I only buy one brand so I'm thinking it's the flavor. what flavor of cat food does my cat like the best?​

Umami.

Explanation:

Umami is the flavor which the cat like the most. This Umami flavor is present in the fish, shellfish, cured meats, meat extracts, mushrooms, vegetables. We know that fish is the most favourite food of cat and the main reason for this is the presence of Umami in the fish. So due to Umami flavor, the fish food is eaten by the cat with more enjoyment as compared to other foods so the person have to provide fish food to the cat for their good health.

this is a good question! i'll do some research and come back when i have the answer!