Whenever I Eat Something My Mouth Emanates Gaseous Breath.it Continues

Whenever I eat something my mouth emanates gaseous breath.it continues even while I'm breathing. Though less stringent, while breathing it causes people around me to sneeze. I had root canal in upper molars a decade ago and braces two decades ago. All the GI tests are normal.what could be the source of these rotting food?
P.S I brush after every meal