re: Mystery solved: This is why the McDonald's ice cream machine never works

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And while other ice cream machines have to be disassembled and cleaned daily—and any leftover contents discarded—McDonald’s Taylor machines use a daily “heat treatment” process designed to jack up its contents’ temperature to 151 degrees Fahrenheit, pasteurize it for a minimum of 30 minutes, and then refreeze it again in a once-a-night cycle, a modern marvel of hygiene and cost savings.

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The machine’s automated nightly pasteurization process, rather than make life easier for restaurant managers, has become their biggest albatross: Leave the machine with a bit too much or too little ingredient mixture in its hoppers, accidentally turn it off or unplug it at the wrong moment, or fall victim to myriad other trivial errors or acts of God, and the four-hour pasteurization process fails and offers a generic, inscrutable error message—meaning that the machine won’t work until the entire four hours of heating and freezing repeats, often in the middle of peak ice cream sales hours.

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