My 4 year old autistic son has a very limited diet. how can i get him to expand his palate?

Lick first, then eat: Have your son lick the food first to see if he wants it, only then do you give it to him to eat. He is probably focusing on texture as well as on how hot or cold it is, then on flavor. This gives him a sense of being able to make food choices and to expand his palate. This technique has worked very well with my grandson who has been helped greatly by the wisconsin early autism project.

Restricted diet.: It is very difficult to expand an autistic kid's diet. Work with a dietician and occupational therapist.