The single greatest limiting factor on how long it takes to cook food is the boiling point of water.
Folks who live at high altitudes know this first hand. Their air pressure is lower, and so their water boils at lower temperatures. (In the mile-high city of Denver, for example, water boils at 204F, and in the camps on Mount Everest water boils at 160F. For those of us at sea level, it boils at 212F.)
Cooking at these lower air pressures affects cook times for many foods since water will begin evaporating sooner and drying out the food more quickly.
Translation? In a low-pressure environment, cooking times on moist foods must be increased. Turning up the heat will not help cook food faster! That’s because the temperature of water will never exceed it’s own boiling point — any higher temperatures and all you’ve got is steam.
Theoretically, if you were at a high enough altitude, you could boil water at room temperature. Boiling, therefore, isn’t really a product of temperature at all, but of pressure!
By increasing pressure, you raise the boiling point of water.
Just as cooking times are lengthened by cooking at the lower air pressure of higher altitudes, cooking times are decreased by cooking at the higher air pressure created by a pressure cooker. That’s why you can pressure cook chicken broth in an hour or two instead of eight or twelve. It’s also why you can pressure cooker grass-fed pot roasts in just an hour as opposed to cooking them in your oven for four.
Because the boiling point of the water inside a united pressure cooker is elevated, you can cook the food at a slightly higher temperature and avoid water loss. In cooking, liquid loss equals over-cooking, drying out, or burning your food. By avoiding water loss while maintaining higher temperatures, your food cooks more quickly.
IS PRESSURE COOKING HEALTHY?
The biggest argument against pressure cooking by those who think it’s unhealthy is that pressure cooking must be bad for the nutrients in the food because you’re cooking them at higher temperatures and higher pressures.
It’s like saying the cooking method is dangerous, well just because! For reasons!
It’s like arguing that food cooked in Miami (where the boiling point of water is 212F) is somehow less nutritious than food cooked in an Andean or Himalayan village (where the boiling point of water is 190F) just because the air pressure and boiling point are higher in Miami.
PRESSURE COOKING PRESERVES NUTRIENTS BY REDUCING COOK TIMES.
It turns out that higher cooking temperatures don’t destroy any more nutrients than lower cooking temperatures. If a temperature is high enough to start destroying heat-sensitive nutrients, then those heat-sensitive nutrients will be lost regardless of whether the cooking temperature is 119F or 350F.
It’s not the temperature that matters, but the cooking time!
By cooking foods for shorter lengths of time, pressure cookers preserve the nutrients better, despite cooking at higher temperatures.
PRESSURE COOKING PRESERVES NUTRIENTS BY USING LESS WATER.
Why do health and nutrition experts always tell you to give preference to steaming vegetables over boiling them?
Because the nutrients leach out of the vegetable and into the water, and then we dump the water out when serving the veggies!
Pressure cooking uses very little water compared to many other cooking methods, essentially acting like a steam cooker where the steam is not allowed to escape easily (thereby building the air pressure). Less water comes into contact with your food to leach away vitamins and minerals.
And if you do as recommended and let your pressure cooker cool naturally before removing the lid so that the steam condenses back into the small amount of liquid in the pot, you can consume all the liquid with your meal and limit the loss of nutrients to water even further.
WHAT ABOUT THE ARGUMENT THAT IT’S UNNATURAL OR NOT TRADITIONAL?
Maybe I’ve convinced you that pressure cooking can be healthy. But you still hesitate because it’s not been a historically embraced method of cooking. Creating a pressure difference like this is unnatural, you say.
Here’s the deal. The difference in the boiling point of water in a pressure cooker vs. Miami (sea level) is the exact same difference found between Miami and La Paz. That translates into WIDELY DIFFERENT cook times for roast — a difference of many hours.
So ask yourself if the roast in Miami is somehow less nutritious or digestible than the roast made in LaPaz. The answer is no.
And that’s because in both places, you cooked the roast until it was done and no longer. Both roasts had the same water loss. The only reason one took far less time to cook was that the higher air pressure meant that you could cook it at a higher temperature before you started losing too much water and overcooking the food.
I get that pressure cookers aren’t traditional, but neither is my convection toaster oven or my immersion blender. In all these cases, we’re just using technology to make our cooking more efficient.
It’s not “unnatural,” but wise to take our breaks where we can get them.
The fact is that the science shows pressure cooking is healthy, that it can preserve more heat-sensitive nutrients than any other cooking method because of its shorter cook times. The fact is that the difference it creates in the boiling point of water is well within the range of a normal difference on this planet.
Again, it’s the same difference we see between Miami and La Paz. If you used a pressure cooker in La Paz, it would mean that you were cooking your food in the length of time folks living in Florida take for granted. Would that be somehow unnatural or wrong? No. It would be like cooking in Miami! And La Pa z isn't even the highest city out there. There are plenty of others that exceed it in altitude by a mile or more. Their boiling points are even lower! Their cook times even longer!
Pressure cookers just use technology and a nifty trick of physics to act like a great equalizer. It just so happens that for those of us who live nearer to sea level, who aren't used to adjusting recipes for altitude and pressure (unlike folks who live at some seriously high elevations), the difference in cook times seems somehow shocking and unheard of.
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