posted by Dave Arnold
For years Nils and I haveÂ maintainedÂ that pressure cooking stocks and broths is the way to go. Weâ€™ve always said that the high temperature in a pressure cooker gives better extraction and meatier flavors than normal cooking. Turns out we were wrong. Sort of.
While I hate being wrong, this particular error taught us a lot –Â including:
All pressure cookers arenâ€™t created equal. The cooker you use affects flavor.
Pressure cooking can be used to modify conventionally cooked stocks.
Not all stock ingredients react the same wayÂ in the pressure cooker.
So whatâ€™s going on? Here is our journey:
I was planning to write a post on the superiority of pressure cooked stock. As a formality, I set up a blind taste test between conventional and pressure-cooked stocks. I had no doubt the pressure cooker would win. I chose white chicken stock because it is simple, doesnâ€™t cook as long as veal, and has fewer variables than a brown stock. We weighed out two identical amounts of chicken, mirepoix, herbs, and water and pressure-cooked one for 45 minutes and let the other one simmer on the stove for 2 hours. We strained both stocks and weighed what was left. The conventional stock had reduced more than the pressure-cooked stock (by 10 percent) so I added enough water to it to equal the volume of the pressure cooked stock. Some of the interns had a problem with this step but it is the only way to compare two stocks properly.
We tasted both stocks blind.
The aroma of the pressure cooked stock was clearly superior. The color was deeper as well (because of this all future tests were done actually blind â€“with our eyes closed). Unfortunately the conventional stock tasted better. It had a stronger chicken flavor and was better balanced overall.
I was distraught. We tasted again. Same result.
I had the interns make another batch of stock. Same result.
Then we decided to test each individual ingredient separately. We did side by side tests of chicken only, celery only, and onion only (the carrot got 86â€™ed by accident). The conventional chicken won. Loss. The celeries were both good, just different. The pressure-cooked one tasted more like celery tea and the conventional one tasted more like soup. Testers almost all preferred the conventional celery. Loss again. The pressure-cooked onion clearly won â€“thank god. Pressure cooked onion had a big, round, sweet flavor. Conventional onion was useless. Win.
The win with the onion broth wasnâ€™t enough to keep Nils and I from being pretty depressed. I lost sleep over the matter. I had one more test up my sleeve.
I took 4 liters of conventional chicken stock from the restaurant and pressure-cooked half while the other half simmered on the stove. This time, I didnâ€™t use the schoolâ€™s pressure cooker, I used my own. When I compared the two stocks side by side the pressure cooked one was far browner. I hadnâ€™t thought the pressure cooker would change the color of a pre-made stock. When we tasted them the pressure-cooker won! Finally.
I then ran the same test with the schoolâ€™s pressure cooker and the pressure cooker lost. WTF?
Turns out all pressure cookers arenâ€™t the same. All pressure cookers reach similar temperatures â€“approximately 250 F (120 C) at 15psi; but the way they regulate pressure is different. The pressure cooker at the school, made by Iwatani, uses whatâ€™s called a jiggler to regulate pressure. A weighted jiggle-top sits on top of a tube.Â The steam pressure builds up in the tubeÂ until it is strong enough to lift up the jiggler and let the excess steam escape.Â The valve makes a continuous chu-chu-chu-chu sound as it operates. You want to adjust the heat so it doesnâ€™t chu-chu too fast, but steam is always going to escape. There is no other way to know whether the pot is hot enough. Theoretically, the pressure gauge on the lid should allow you to cook just below the point where the jiggler lets steam out, but in practice the gauge doesnâ€™t work properly.
Another common pressure regulator on inexpensive pressure cookers uses a rotating switch that allows you to set the pressure at 15 psi, 5 psi, or to release the steam pressure entirely.Â This type of regulator also requires escaping steam to indicate proper pressure.
My pressure-cooker, made by Kuhn Rikon, uses a different type of regulator.Â It has a spring valve that moves up and down; itÂ both regulates and indicates pressure. When the valve stem rises enough to see the first red ring you have 5 psi.Â When you see the second red ring you have 15 psi. No steam escapes. If you heat the pot too much it lets steam escape to tell you to turn the flame down.Â Once you comply it goes silent again. Nice.
I have known for a long time that less liquid evaporates in my pressure cooker than in the other types.Â This becomes especially apparent when you are cooking for several hours as we sometimes do (for softening spices, etc).Â I hadn’t thought that the escaping steam would affect taste as well, but IÂ should have -Â it makes sense.
We ran one more test. Conventional for 1.5 hours vs. the schoolâ€™s pressure cooker for 45 minutes vs. my pressure cooker for 45 minutes vs. the schoolâ€™s pressure cooker for 20 minutes (in case we had just been cooking too long and blasting the flavor away).
My pressure cooker won, followed by the conventional cooking;Â both of the schoolâ€™s pressure cookers scored lower. I feel a lot better.
But we still need more tests. And more will come.
PS: Many cooks have an intutitive feeling that pressure cooking stocks is a bad idea.Â Their reasoning isn’t related to the previous discussion and isn’t born-out by our tests. Here are the reasons they usually give (and my responses):
- Pressure cooking will make the stock cloudy. That is incorrect. The boiling in a pressure cooker is no more violent than in a pot, so stocks donâ€™t get any cloudier. We have done many side-by sides to prove this.
- Pressure cooking extracts bitter components. No one has detected bitterness in pressure cooked stock weâ€™ve made.
- Not being able to skim the stock will introduce off-flavors. We have not noticed this in any of our tests.