Food -> Stomach=how long
Nothing from your throat to your pouch has changed. But your stomach is now a pouch. Because the upper part of your stomach was made into a new pouch and the remnant is farther down to your left and still producing and releasing gastric juices farther down in your intestines. This is probably why so many people have some pain lower left and mid right after surgery as those are the new connections so to speak. It takes as long for your food to reach your pouch POST op as it did PRE op because nothing has changed from your pouch up to your throat.
I'm pretty sure it did not take 20 minutes for food to move from your mouth, down your esophagus into your stomach preop. It probably took less than 20 seconds. And since your mouth and esophagus are still the same post op, it probably doesn't take any longer now.
Please note: I AM NOT A DOCTOR. If you want medical advice, talk to your doctor. Whatever I post, there is probably some surgeon or other health care provider somewhere that disagrees with me. If you want to know what your surgeon thinks, then ask him or her. Check out my blog.