I have 2 things to recommend. First, if there is a filter for the water (there should be) to change it. If the water line does not have a filter, add it. The second recommendation is to get a small back of the cheap bbq charcoal brickettes. Not the easy start, but plain charcoal. This stuff is even more effective than baking soda at keeping odors down. I have 3 in the fridge and 3 in the freezer, in the door part in a disposable plastic cup. I have 4 in a margarine bowl in the chest freezer.
The charcoal is also wonderful to place in shoes (insert in old socks) to keep odors down, and to place in ice chests or thermoses to prevent odors.