It is possible but the results aren't always 100% satisfactory. The TA Specialties Alize chainrings are designed to work with Shimano triple cranksets. You could replace your rings with 50-39-28 but shifting performance may not be quite as good as what you now have. You should also consider a complete crankset replacement from TA or FSA. Also the Shimano 105 10-speed crankset has 50-39-30 chainrings. It may work OK with a 9-speed drivetrain.
With some research you may be able to find a touring specific front derailleur designed for smaller chainrings. A mountain style FD won't work.
The front derailleur will need to be lowered to work with smaller chainrings. If your front derailleur is a braze-on type, the more common type now, it probably won't go low enough for a big ring smaller than a 50. That won't be a problem if you have a clamp-on FD.
Try shopping for TA Alize rings at
http://www.peterwhitecycles.com and
http://sheldonbrown.com.
Al