We've been using a Foodsaver for years, both at home and on the boat. Great product!
According to the Foodsaver website, their bags are made of polyethylene with a coating of Nylon on the outside for stiffness. Polyethylene will not produce any harmful products when heated to the temperatures found in a pressure cooker, so that wouldn't be an issue. No bisphenyl A or anything like that. The temperatures in a pressure cooker reach about 121* C (250* F), so not all that high, actually.
I'm not a food scientist or microbiologist, so I can't assure you that treating the vacuum-sealed food bags in a pressure cooker would render the food as safe as if done in glass jars, but I suspect that it would, simply because the only difference is plastic versus glass. The temperature attained is what sterilizes the food and packaging.
We've extensively used our Foodsaver to make dinners for offshore
passages, but we've always frozen them after sealing--never tried the pressure cooker trick. On one passage
, on a friend's boat, we were dealing with an engine
driven fridge (no freezer). The dinners had been frozen when we put them in the fridge, but slowly thawed over the five days before the engine
failure, at which point they warmed up to ambient temperatures. We (four guys) continued to eat them with no ill effects, but I have to report that the last one (ratatouille, so no meat) was a bit "fizzy" after being warm for five days. Nobody died, so all was good. We switched to freezed dried rations like the owner had used in Viet Nam after that. Now, that was truly awful!
You might want to contact Foodsaver about using their product for "canning". They may have done some studies, who knows.