I don't always burn applesauce. Sometimes I can suck-it-up and not burn it.
But then I push the envelop. I turn the heat just a little higher. I use just a tad less water in the bottom of the kettle. I add a few more apples.
And then I burn the applesauce.
The batch of apples I was cooking down to mush is ruined.
The kettle is impaired. I have to scrub, and scrub and scrub...and even then apples cooked in the kettle pollute future ventures.
I am also an engineer
In theory, a double-boiler where the intermediate fluid has a boiling point significantly above the boiling point of pure water but far below the temperature that scorches apples would create a very robust process.
Commercial canneries use pressurized steam. Water is cheap but equipment is not. The fixed costs of the steam equipment is amortized over enough volume that it become insignificant. That is not the case for the typical, home canner.
The next best thing would be to use an ethylene glycol-water solution as the intermediate fluid. My first swing at the pinata was to use a 2/3 EG:1/3 water solution with a boiling point of 236F...almost 25 degrees higher than pure water.
My concern was that the EG:water solution would boil and over-flow into the apples, thus contaminating them.
I investigated that concern by performing a trial run with the EG-H2O solution and using a full kettle of pure water as the test load.
This is what I found.
|A turkey fryer. Nominally 55k BTU/hr. Sides modified to accept larger diameter double boiler. I cranked it up as hot as it would go to give it a severe test.
|Three nuts to hold cooking vessel away from the bottom of the double boiler.
|1.5 gallons of 65%:35% antifreeze:H2O. Large kettle has ID of about 15.5 inches. Smaller kettle has ID of about 11.5 inches.
|Started at 11:36 AM. H2O payload hot-to-touch at 12:06. Antifreeze:H2O heat-transfer fluid bubbling at 12:11. H2O in cooking vessel at rolling boil at 12:20.
The results of this trial run are promising enough to redo the experiment with real apples.