Yesterday I had the most delicious chicken salad.
Shortly after I ate it, I was seized by hours’ worth of spicy burps. My office smelled like a delicatessen by the end of the day, I’m sure. As much as I liked the salad, I didn’t enjoy the encore quite as much. 
I don’t know flavors well enough to be able to discern the spice(s) that did this to me. But it’s happened to me before–especially with Indian foods. Why? Is it indigestion? What exactly is indigestion and why do only some spices trigger it? And what is the mechanism that makes some burps aromatic and others not?
Things that make your burp require specific gut bacteria to work hard. Different chemicals and components of various foods press the gut bacteria into service. Their hard work has a byproduct called ‘gas’.
Why a spice is smellier than the next probably has to due with how successfully broken down that spice is and how far along in the gut the spice has gotten.
Foods that make you burp give up the goods earlier on in the digestive process (stomach), whereas foods that cause flatulence are getting a fair am’t of attention later in the intestine, and the flatulence is really a byproduct of gut bacteria going to town.