Coworkers Who Burp

Is there etiquette on how to tell a coworker to stop burping?

I have one coworker who does not care to let one rip at least once an hour. I find this particularly annoying because first of all, gross. And secondly, we are the only two people in a room together. So every time this person burps, it's pretty much AT me.

I don't have much of a relationship with this coworker. He is new to the job. We have only known each other a couple of weeks, so you would think he would be insecure to burp so much around me. Nope. I think he secretly likes it.

It really does gross me out, but I don't know him well enough yet to tell him to stop being disgusting. How can I break it to him gently?