It may be worth taking him to a doctor- I've been told by my parents that I began to refuse milk at 13 months old and it was discovered that I was allergic to milk, which explained why I vomited so much as a baby (the doctors had put it down to reflux). It may not be the texture of the food that is bothering your son, it may be an allergy or intolerance to a particular chemical that happens to be present in the foods he is refusing. It was later discovered that I was allergic to the protein substance in milk, not the lactose- it is possible your son has an allergy to a specific protein. Good luck!