Eating Problem

I got problem of feeding my 20mth old son, he refuse to chew his food before swallow and turn out vomitting out all his food even give him apple he also dont like coz need to chew it, not like before when he still baby, he like apple very much. Anyway trick can share with me to let him chew the food coz I have try many way to teach him chew the food but he still refuse to chew it