Why do I have throat pain IMMEDIATELY upon eating foods which exacerbate GERD?

I've been diagnosed with acid reflux by a pretty thorough series of tests by one of the foremost experts in the world (Dr. Steven DeMeester of USC). I'm almost sure that's what my problem is. Maybe I have others too, but one thing I've wondered about for a while and I realized today I never asked him was why I usually have symptoms immediately upon eating acidic food (i.e. any food which causes symptoms of GERD). My understanding is that the stomach must first begin digesting the food in order for acid to be produced and then reflux into the esophagus and/or throat. So how can I experience pain immediately?