It could also be due to the fact that when stomach acid enters the duodenum it signals the entire digestive process. That's why having low stomach acid is such a problem. It's the stomach acid that triggers the next phases of digestion like the liver and pancreas. So maybe your dumping out some acidic stuff and your body thinks it's a broken down meal ready to get digested.
Either that or you have loaded way above bowel tolerance and your body is just trying to flush it out ASAP and your seeing food that wasn't completely finished digesting.