Well the simple answer is that since the recipe is intended for fridge storage and not canning then that is what you should do. Whether or not it can be safely canned is unknown so your personal choice.

IMO it is more dense than the plum sauce would be so that would affect the processing time. And normally foods are cooked before they are pureed so that bothers me a bit in the instructions. On the other hand plums are a little more acidic than tomatoes so the pH would probably be safe but without measuring it I can only guess. I suppose you could always pressure can it for extra safety.

Would I can it? No. I don't can untested recipes, especially not unusual things I might not even like just to use the produce up. If I can't find an approved recipe for canning something good with it then I just can the plums or whatever plain to save them and make ketchup or all kinds of other things out of them later. Plain canned or frozen plums have all sorts of uses.

But it boils down to the level of risk you are comfortable with and how badly you really want Plum Ketchup. ;-)

Dave

Thank you, Dave. I really did want to try the plum ketchup, but after I gathered the plums to soak in vodka for liquer, there were not enough left to give the recipe a try.