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I’ve been doing a bit of research into pressure frying and I’m curious to hear if anyone has thoughts on why commercial pressure fryers do not typically exceed 12-15 PSI.

According to Henny Penny’s literature, their pressure fryers operate at 12 PSI with an oil temperature of 325 F. At 12 PSI, the boiling point of water is roughly 245 F so there’s an 80 F difference between the oil temperature and water boiling point. Even at this relatively low temperature, pressure fried chicken is roughly 30% faster than atmospheric fried chicken. Wouldn’t we be able to fry chicken even faster if the pressure and temperatures were increased? Why do you think 12 PSI is industry standard?

An extreme example would be oil temperature at 450 F and pressure of 155 PSI. This would yield a boiling point of 370 F and would maintain the 80 F differential between oil and boiling point. This would likely require extra thin pieces of chicken to fully cook before the breading burnt, but I’d imagine there’s a point somewhere between 12 PSI and 155 PSI that would allow for much faster frying times without burning the breading.

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Well, Ecnerwal mentioned the safety issue. Such a pressure cooker would also need a (much, much) more powerful heating element and probably a complex recirculator, since it starts at ambient pressure and needs to hit peak pressure before you're done cooking.

But mostly: The point of pressure frying is not to save time. The point is to produce crispier, juicier food by heating more quickly. That only works up to a certain point, after which the coating burns. It's possible that there's some food which could benefit from being pressure-fried at extremely high pressure/temperature, but fried chicken isn't it.

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Accidents and failures.

12-15 lb steam is no joke if things go wrong, but it's a level that has a wide array of adopted practice and engineering for home use and kitchen (home or commercial) use. A boiler operator's license is not required for operating these devices safely.

A steam explosion resulting from 155 PSI (10.5 bar) steam would be far more disastrous - likewise, the pressure vessel to contain it would have to be far sturdier. In most areas, operating such a device would indeed require a boiler operator's license. Early in the age of steam folks who thought like you are thinking were free to implement their high-pressure schemes, and they managed to kill people, and laws resulted in most areas that limit the steam pressure that can be used in devices accessible to unlicensed operators.

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    For your entertainment, an easy to read overview of the development of steam vessels and "accidents" can be found in the first part of Nancy Levenson's paper (PDF warning): High_Pressure_Steam_Engines_and_Computer_Software. (In the remainder, she draws parallels between the requirements for safe steam engines and the development of safety-critical software.) Nov 11, 2022 at 13:03

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