Originally Posted by mtnagel
If starsan is good enough for sanitize while you are fermenting, I don't see why it wouldn't be good enough for the washed yeast.
I think you are asking a bit more out of the sanitization when washing yeast. With an ordinary fermentation, you have very active yeast that will outperform most potential infections. By the time the yeast slows, you have a high alcohol environment that will inhibit anything that survived. It's only the relatively few bacteria or wild yeasts that can tolerate the alcohol that cause problems.
In a yeast rinse, you are doing everything you can to obtain yeast+water and put the yeast into a dormant state. In that situation, it seems at least plausible that the environment is more hospitable to infection by organisms that would normally be overwhelmed in a beer. Boiling (especially in a pressure cooker) will do a more thorough job of sanitizing, in some cases reaching sterilization.
This is speculation, though, and there are good counterarguments: the rinsed yeast are stored in a cold environment; the stored slurry has less food to make it an enticing habitat for bacteria; and it doesn't do any good to start with a sterile jar if you don't have a completely sterile process for handling and filling it.
While going through my last rinse, I was wondering the same thing, though. It was a pain to boil the jars and lids. I suspect in most cases you'd be fine either way, and probably the most effective approach would be to boil so you can start with a near-sterile jar, then use contact sanitizer to protect against infection during the rinse. If anyone has concrete information about this, I'd be interested.