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High Altitude Pressure Cooking and Stock Preparation


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Modernist Cuisine(page 2-291 et seq.) has an extensive discussion about using pressure cookers and pressure canners to make stocks, and their conclusion is that cooking the stock at 1 bar or 15 psi over ambient, resulting in a temperature of 121C, generally produces the best results, although some recipes call for using an autoclave at temperatures up to 130C.

However, as I live in Taos, NM, at an altitude of 7000 ft/ 2133 m, some adjustment is required. To reach the same temperature, I would have to run the pressure up to 18.5 psi. Unfortunately, most pressure cookers either use "jiggle" weights or spring loaded valves which come in 5, 10 and 15psi increments. Also, most pressure cookers don't have an independent pressure gauge, and none that I am aware of have a means to actually measure the temperature of the water/steam, much less the temperature of the stock or other food you are cooking. In addition, experiments by Dave Arnold and Nils Norén have shown that pressure cookers that vent the steam cause an undesirable cloudiness in the stock, and some loss of flavor/quality, perhaps as a result of venting the aromatics. And finally, without venting steam, it is difficult to maintain a desired pressure/temperature, even with a pressure gauge, unless you are willing to stand there and monitor the pressure and adjust the gas flame.

There had to be another, better way. After discussing this with Douglas Baldwin, I bought a 25 qt. All-American Sterilizer, model 1925X, and proceeded to modify it to use a PID controller, the Sous Vide Magic (SVM) controller from Fresh Meals Solutions, to control an electric griddle to control the temperature, and a second SVM to monitor the temperature within the stock pot.

I removed the pressure regulator, fitted a T-adapter, threaded two SVM probes through it, and then reassembled the regulator. Now I can bring the water in the sterilizer to very close to the boiling point, drop in a stainless steal pot (an All-Clad Pasta Pentola) with the stock, secure the lid, and let the pressure build up. I can vent the steam manually, or not, as I see fit. And if I am canning something, I can monitor the temperature inside a jar filled with water to make sure it is getting hot enough to sterilize the food.

For further details, seehttp://freshmealssolutions.com/index.php?option=com_k2&view=item&id=71:high-altitude-pressure-cooking-and-stock-making&Itemid=100088.

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Modernist Cuisine (page 2-291 et seq.) has an extensive discussion about using pressure cookers and pressure canners to make stocks, and their conclusion is that cooking the stock at 1 bar or 15 psi over ambient, resulting in a temperature of 121C, generally produces the best results, although some recipes call for using an autoclave at temperatures up to 130C.

However, as I live in Taos, NM, at an altitude of 7000 ft/ 2133 m, some adjustment is required. To reach the same temperature, I would have to run the pressure up to 18.5 psi. Unfortunately, most pressure cookers either use "jiggle" weights or spring loaded valves which come in 5, 10 and 15psi increments. Also, most pressure cookers don't have an independent pressure gauge, and none that I am aware of have a means to actually measure the temperature of the water/steam, much less the temperature of the stock or other food you are cooking. In addition, experiments by Dave Arnold and Nils Norén have shown that pressure cookers that vent the steam cause an undesirable cloudiness in the stock, and some loss of flavor/quality, perhaps as a result of venting the aromatics. And finally, without venting steam, it is difficult to maintain a desired pressure/temperature, even with a pressure gauge, unless you are willing to stand there and monitor the pressure and adjust the gas flame.

There had to be another, better way. After discussing this with Douglas Baldwin, I bought a 25 qt. All-American Sterilizer, model 1925X, and proceeded to modify it to use a PID controller, the Sous Vide Magic (SVM) controller from Fresh Meals Solutions, to control an electric griddle to control the temperature, and a second SVM to monitor the temperature within the stock pot.

I removed the pressure regulator, fitted a T-adapter, threaded two SVM probes through it, and then reassembled the regulator. Now I can bring the water in the sterilizer to very close to the boiling point, drop in a stainless steal pot (an All-Clad Pasta Pentola) with the stock, secure the lid, and let the pressure build up. I can vent the steam manually, or not, as I see fit. And if I am canning something, I can monitor the temperature inside a jar filled with water to make sure it is getting hot enough to sterilize the food.

For further details, see http://freshmealssolutions.com/index.php?option=com_k2&view=item&id=71:high-altitude-pressure-cooking-and-stock-making&Itemid=100088.

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Interesting, but I wonder if all this is really necessary.

I have an WAFCO All-American pressure canner that is more or less the same thing you have, with a different top. Stocks don't strike be as acidic enough to particularly worry about the fact that it's made of aluminum, and none of the stocks I have made in there have suffered from metallic taste. So putting a stainless pot in there is probably a waste of capacity. I have also had perfectly good results in converting it to a "virtual unvented pressure cooker" simply by putting the weight on the vent at 15 PSI, placing 3-4 quarters on top of the weight, keeping my eye on the pressure gauge and backing off the heat when the pressure hit 18 PSI or so over atmospheric.

The one way that you may have a real advantage is in knowing the actual temperature inside the cooker. When pressure canning, the only way of being sure of the temperature is to vent steam for 10 minutes or so that the entire interior is filled with water vapor and not air. If the pressure cooker is not vented, the temperature is certainly not as high as one might suppose it is.

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good topic. I live at 5280 and have a pressure cooker that I check the temps with an IR thermometer and the only way I can get it up to 245, is to put a couple quarters on top of the pressure cap...works very well..

Bud

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Interesting, but I wonder if all this is really necessary.

I have an WAFCO All-American pressure canner that is more or less the same thing you have, with a different top. Stocks don't strike be as acidic enough to particularly worry about the fact that it's made of aluminum, and none of the stocks I have made in there have suffered from metallic taste. So putting a stainless pot in there is probably a waste of capacity. I have also had perfectly good results in converting it to a "virtual unvented pressure cooker" simply by putting the weight on the vent at 15 PSI, placing 3-4 quarters on top of the weight, keeping my eye on the pressure gauge and backing off the heat when the pressure hit 18 PSI or so over atmospheric.

The one way that you may have a real advantage is in knowing the actual temperature inside the cooker. When pressure canning, the only way of being sure of the temperature is to vent steam for 10 minutes or so that the entire interior is filled with water vapor and not air. If the pressure cooker is not vented, the temperature is certainly not as high as one might suppose it is.

Interesting point that you make. I confess that I have a perhaps irrational bias against plain (non-nonstick) aluminum pots.

It's true that you can buy a different top for the All American Sterilizer that will convert it to a "regular" canner, if that's what you want. Even cheaper, I think you could replace the pressure regulator with more conventional jiggle weight.

What altitude are you working at?

Bob

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Interesting point that you make. I confess that I have a perhaps irrational bias against plain (non-nonstick) aluminum pots.

It's true that you can buy a different top for the All American Sterilizer that will convert it to a "regular" canner, if that's what you want. Even cheaper, I think you could replace the pressure regulator with more conventional jiggle weight.

What altitude are you working at?

I'd probably be happier if it were lined with stainless or something like that (although I understand this would probably be impossible to do at this size and thickness of material). And I wouldn't cool tomato sauce in it or make a gigantic batch of gastrique.

I am in NYC, so compensating for altitude is not an issue. My procedure of putting quarters on the jiggle weight was entirely predicated on the idea of making the venting pressure canner (and pressure canners must be venting) into a non-venting pressure cooker for making stocks, based on the premise that stock quality is better when the cooker is non-venting.

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The generally accepted rule for high-altitude pressure cooking is to increase the cooking time, and not the pressure.

In theory, it should give you the same results - because, after all, pressure shortens the cooking time by raising the cooking temperature so a lower temperature would require a longer cooking time.

I have not ACTUALLY tried this because I live at sea level on the shores of the Mediterranean Sea, but a few of my readers live in Colorado and have been able to pressure cook all kinds of recipes just by lengthening the cooking time.

Here are the instructions by Fagor...

"If you are cooking at high altitudes the cooking times must be longer, as water and cooking liquids come to a boil more slowly. A rule of thumb to remember is to increase the cooking time by 5% for every 1,000 feet above the first 2,000 feet ( 3,000 feet above sea level, add 5% to cooking time; 4,000 feet, add 10% ; and so on). Since the cooking times increase at altitudes higher than 2,000 feet, you will also have to add more cooking liquid to compensate. There are no fixed rules, so try increasing the cooking liquid by approximately half the percentage of the additional cooking time. For example, if the cooking time is increased by 10%, increase the cooking liquid by 5%."

http://www.fagoramerica.com/about_us/article_library/about_pressure_cooking#Pressure

Ciao!

L

hip pressure cooking - making pressure cooking hip, one recipe at a time!

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LFMichaud said:

Interesting project! I would like to see pictures of your modifications of the lid. If I understand correctly with the 25psi relief valve we should be able to reach 130C at sea level.

Yes, according to the pressure gauge, 25 psi should equal 130C at sea level.

The only modification was to unscrew the pressure relief valve,and then screw it back into a T-adapter of the same thread type. Then I threaded two sensors through a brass cap that I had drilled out, filled it with epoxy, and screwed it onto the T.

I"m contemplating removing the pressure relief valve entirely and capping it, relying on the PID controller to keep things from getting too hot and blowing the secondary relief plug. But that would mean that I could no longer vent the hot air until it turns to steam, which is highly desirable for canning and the intended use for sterilization, although venting isn't recommended for making stock. Maybe I can find higher-pressure relief valve somewhere.

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