Boyfriend smacks his food

HELP, I’ve been dating this guy for 2 years now. I never noticed he chewed with his mouth open until a little bit into our relationship and it drives me nuts. It is my biggestttttt pet peeve. Now with how close we are, I’ve opened up about it because I start to get short tempered with how loud and constant it is. I can literally hear him eating from a different room. In the car I’ll have to play music to drown it out. I know I know, I sound so dramatic lol His whole family is the same exact way. I just think it’s sort of embarrassing when I bring him around my family for dinners and things or even just friends. He knows how I feel about it but says he literally can’t chew with his mouth closed. He says he’s a mouth breather and it’s impossible for him. I want to show him what it sounds likes and how obnoxious the noises are but I really don’t want to hurt his feelings or have him think I’m mocking him. What are your guys’ thoughts on this one?