It's probably food particles.
Usually you can clear these by forcing water into the air break exhaust hose with a garden hose.
They sell adaptors that match garden hose thread with sink aerator thread, along with various plastic transition pieces that will mate with the inside or outside of the air break hose.
I can't see this type of jam putting up much of a fight against 50 PSI water pressure but in extreme cases you will have food coming out of the vent pipe and landing on your roof. Then you have to plug the vent opening to maintain the high pressure!
Great fun. . .