I do a great deal of freeze drying with my Harvest Right machine. I've held back on potatoes because because of the oxidation issue. How do I keep my sliced, or diced potatoes from oxidizing while I process them for the freeze dryer? I assume that I can put them straight from the water into the freeze dryer without drying them off because the freeze dryer will remove the moisture during it's processing. Can I just soak them in the cold water/lemon juice bath, or do I need to blanch as well?

You answered your own question, using lemon/lime (or vinegar) for the water holding followed by blanching. Blanching is indeed the secret to preserving potatoes for this method. If you don’t blanch, the starches convert to sugars, causing not only some oxidation but it changes the final cooking chemistry along with potato discoloration and darkening.