Canning applesauce - water bath after the fact
They can be reprocessed, but you will need to at least double the processing time, and you should be prepared to sacrifice one jar of preserves. If you have a pressure cooker, that is the most preferable way to go. If you don't, then a large double-boiler will do. Time your first batch of jars. As you water bath them, allow them to boil for an hour, then open one jar to check the temperature with a cooking thermometer. You need to be sure that the very center of the applesauce gets hot enough to kill bacteria. Once it reaches that temperature, keep boiling the jars for at least another twenty minutes to ensure a complete kill. Your temperature-testing jar should not be kept, so that's the one to use right away.

If, like me, you recently broke your thermometer in an unfortunate accident with a wildly enthusiastic stick-loving canine and haven't replaced it yet, water-bath your jars for at least three hours to make sure they have reached the sweet zone for temperature.