I had the same issue for 2 weeks after my Nissen. When I woke up every morning my tongue was coated with a yellowish white substance; just horrible. It went away as fast as it came. Brushing my teeth and tongue did not seem to help. I also had a bizzare change in my taste buds. Nothing tasted like it had enough salt. Fortunately these symptoms have gone. Now I just wish the gas would go away.