by Dave Arnold
Warning! I do this for a living. Following my path will void your warranty and expose you to possible injury or death.
I love pressure cookers. They were designed to cook quickly and save energy, and also to sterilize and can foods. But that’s not why I love them. Pressure cookers can create new flavors, amp up old flavors, mollify harshness, and alter texture. I’ve done many dozens of pressure cooker demonstrations. At every demo, someone asks me what I think of electric pressure cookers –specifically, the well-known model from Cuisinart. And then I am forced to admit that I have never used one. And then friends like Jeffrey Steingarten (who loves his Cuisinart pressure cooker) chide me mercilessly.
Someone from the Cuisinart corporation heard my sad story and sent me a unit to test (thank you, kind patron –I lost your note, so please send me your info).
Pressure cookers in a nutshell:
The boiling temperature of any liquid is dependant on pressure. The higher the pressure, the higher the boiling point. Pressure and boiling temperature are inextricably intertwined: tell me one and I’ll tell you the other. Pressure cookers elevate cooking temperatures by increasing pressure in a way that isn’t entirely obvious. In an oven set at 400 F, the inside of a piece of meat will never go above the sea-level boiling point of water –212 F (100 C). In a pressure cooker, the inside of the food can get to much higher temperatures.
There is a worldwide standard for pressure cookers: since the early 1900’s they have had a high-pressure setting of 15 pounds per square inch (psi) over atmospheric pressure. At sea level, water at 15 psi boils at 250 F (121 C ) instead of 212 F (many pressure cookers also have a lower pressure setting between 5 and 8 psi at 227-235 F or 108-113 C).
What’s so special about 15 psi?
Both temperature and pressure affect the way your food cooks. Most pressure cooker recipes are written for 15 psi. If a cooker can’t reach 15 psi, those recipes won’t work. If you are using your pressure cooker simply to reduce cooking times, dealing with pressures under 15 psi is no big deal — just increase the cooking time a bit. But I rely on the pressure cooker for more than faster cooking. Many of the pressure cooker recipes I’ve developed rely on the 250F that you get at 15 psi to produce special effects, like obliterating the stink from garlic and onions, and taming the pungency of mustard seeds and horseradish. These recipes don’t work at 9 psi. If you eat 4 heads of garlic that have been pressure cooked at 15 psi or higher for 20-30 minutes, you can have a discussion with your friends about it the next day. At 9 psi, don’t subject them.
A pressure cooker at 15 psi makes stocks and meats taste… well, meatier. I have run tests of chicken stock made at 8 psi versus 15 psi; I definitely prefer 15 psi. Wondering if even higher pressures would produce better results, I ran a series of tests a while back on stocks with the huge, expensive, pressure-accurate All American Pressure Sterilizer from WAFCO to see. I tested to 24 psi. Turns out, 15 psi is the magic number; see here. Pushing pressures to an extreme, I’ve sealed potatoes in a pipe and thrown them in my deep-fryer set at 365 F, generating 148 psi. Wow, did those potatoes taste bad. Brown all the way through and gross. Possibly the worst stuff ever (see here).
The Problem With Electrics:
The main problem with many electric pressure cookers: they don’t follow the 15 psi standard. This deviance has nothing to do with the fact that they are powered by electricity.
The Cuisinart has both low and high pressure settings, but unfortunately the manual doesn’t tell you what those settings mean. I needed to figure out the pressures and temperatures myself. I couldn’t find a good way to measure pressure directly without drilling holes in the cooker, so I decided to measure temperature, instead, by inserting a thermocouple into the unit through the vent hole and then sealing it up. I measured a low pressure temperature of 230 F (110 C), corresponding to 6 psi. At high pressure the unit reached 237 F (114 C), corresponding to 9 psi — below the magic 15.
There are Many Good Things About the Cuisinart:
- It is non-venting. Most pressure cookers vent steam from their lids to regulate pressure. The Cuisinart doesn’t. Some of my tests show that for certain applications, like making stock, pressure cookers that vent while cooking produce drastically inferior flavors. See here. (PS, you can follow a tip from Modernist Cuisine and make small quantities of good and sterile stock in mason jars –even in a venting pressure cooker). This is a big plus for the Cuisinart.
- It heats up the house less than a stovetop unit.
- It doesn’t take up a burner.
- For something that cooks, it isn’t an electricity hog (1000 watts max).
- It doesn’t scorch — a constant danger with a stovetop unit.
- It is easy to clean because of the non-stick cooking surface.
- It is bonehead simple to use, and, unlike any stovetop unit, it’s foolproof. It shuts itself off when it is done, and goes into a keep-warm mode.
- It has good capacity (up to 16 cups, but I’d never add more than 12).
- You can simmer, brown and saute in it.
- You can buy it for under 100 bucks (my stovetop Kuhn Rikon is over $200).
OK, I Like Those Benefits; But I Want 15 Psi, I Need 15 Psi. Now What?
Warning: Technical Section
Here is the part where I void my warranty. I flipped the unit over, took out the two screws and popped off the protective plate. The temperature sensor was located on a spring-mounted button in the center of the unit and had two black wires coming out of it. I popped the connector off the circuit board and measured the resistance of the sensor as I changed the temperature with hot water. Boom. It was a simple temperature-dependent resistor (RTD), and the resistance went down as the sensor got hotter. So far, so good.
I filled the (unplugged) pressure cooker with oil and put in an immersion circulator set to 238 F. After the circ reached temperature, I measured how many ohms the sensor was reading: 5080. I then set the circulator to 250 F and read the resistance after the oil got to temp: 4110 ohms. I figured if I added 970 ohms to the circuit I’d be gold. I soldered in a 10 turn trimming potentiometer (variable resistor) into the circuit, set it to 970, and began testing.
I figured I’d just let the pressure cooker heat the oil with the lid off, and the temperature sensor would tell the machine to shut off once it reached 250 F. Wrong. The temperature went to 290 F before I pulled the plug. After much testing, wailing, and gnashing of teeth, I discovered that to regulate temperature the machine must be under pressure. I don’t really understand it. I don’t know how the unit knows it is under pressure (I could find no easily accessible pressure sensor), but it does. I had to go back to measuring the temperature through the sealed lid, which I did with an improved thermocouple rig (a piece of wine cork and a hypodermic probe). The temperature was higher than before -244 F (118 C) but not high enough. I cranked the potentiometer to 1500 ohms and got a temperature of 254 F (123 C). I dialed it back to 1270 ohms and got a friendly 249 F (120 C). Close enough for me.
End of Technical Section
Real World Cooking Tests:
I decided to test the Cuisinart against my old stalwart Kuhn Rikon stovetop model in making Hamine eggs. Traditional Hamine eggs have been cooked for a day or so and take on a brown color due to low temperature Maillard reactions. Years ago, we figured out you can make them in a pressure cooker (see here). Let the eggs come to boil in the pressure cooker, simmer for 5 minutes, seal the cooker and cook at 15 ps from 40-60 minutes. The longer and hotter you cook, the browner the eggs and the more intense the Hamine egg flavor.
Eggs cooked for 50 minutes in my Kuhn Rikon were slightly browner than those cooked in the Cuisinart at high-pressure. Either I hadn’t fudged with the temperature properly in the Cuisinart or my Kuhn Rikon was running a bit high –I think the latter. You regulate the Kuhn Rikon’s pressure by adjusting the heat on your stove till you see the red rings on its spring-loaded valve. I always push the valve a little past the second ring, so I probably go slightly above 15 psi. The 60 minute Cuisinart eggs were as brown as the 50 minute Kuhn Rikon eggs. The 40 minute Cuisinart eggs were, duh, lighter than the others, as was the 50 minute low-pressure Cuisinart Egg.
With the modifications I made, the Cuisinart might be my go-to pressure cooker. In fact, I’m cooking turkey thighs in it right now. I do, however, have some reservations:
The Negative Points of the Cuisinart:
- You have to modify it to get it to cook at 15 psi.
- It doesn’t tell you the temperature at which it’s running.
- There is no way the Cuisinart it is as tough as my Kuhn Rikon. My Kuhn Rikon pot is built like a high quality stockpot; the cooking portion of the Cuisinart is basically a non-stick coated rice-cooker insert. I use metal utensils in my Kuhn without hesitation.
- It beeps at me.
Time Will Tell:
I am unsure how durable the unit will be. Two points of concern: overheating because of my modifications, and the possibility that the insert will get damaged by typical use. My similar rice-cooker insert is OK after years of hard service (Zojirushi makes good stuff), but pressure cooking queen Miss Vickie dislikes non-stick pressure cookers, presumably because of durability. She also says that the reason electric pressure cookers are set to a low pressure is that they can overheat. Time will tell.
66 thoughts on “Voiding Your Warranty: Hacking Electric Pressure Cookers”
This might be the best thing I’ve read in weeks. How did I not know about this blog?
I bought the cuisinart PC a few months ago, and have often about the PSI it reaches while under high pressure, after having read your earlier post on pressure cooking, I just hoped it reached 15. This was an amazing post! I’m in the city, any chance I can have you hack mine to get to 15 psi? I don’t trust myself with a soldering gun.
I only void my own warranties. The good news is that soldering is easy to pick up and a good skill to have!
Good work! If you had put a notch in your belt for every warranty you’ve voided, how many notches would your belt have now?
Slight error on your part: I’ve had an electric pressure cooker for three years, not the Cuisinart, which I believe was introduced after mine, but the Russell Hobbs “Nutritionist.” The company is a British maker of generally upscale small electricals, as they’re called. Mine looks much nicer than the Cuisinart.
Nonetheless, you’ve made me paranoid about my Russell Hobbs. I believe I needed to call them to discover the putative PSI inside my cooker. When I produced various chicken stocks using the Modernist Cuisine’s streamlined methods, the timing seemed way off.
Is it possible to hire a pressure-cooker hacker? Do you rent out your students? Or should I be able to adapt your Cuisinart narrative? And why do you need to use temperature? Can’t you construct a pressure-gauge that doesn’t return to sea level when you open the cooker, something that simplhy gets stuck? Like a can of Diet Coke?
It would be possible to use a pressure logger or similar. That would be the best way. I don’t have one –I can look around. I’ll give you a call next week.
Thanks for this, great post as usual.
I noticed the original Hamin Egg mention but I assumed there are things you aren’t mentioning there since I would assume the pressure would crack the eggs or at least collide them against one another thus cracking them. Do you do anything special to prevent them from cracking?
Crack prevention is done before the lid goes on. Start from cold and ramp up the temp fairly slowly so the air has time to escape the shell. Don’t puncture the shell. Let simmer a few minutes being careful not to let the eggs knock around, After you seal the pressure cooker, there is very little actual boiling, so the eggs don’t move around much. After the cooking is over, let the pressure come down naturally. Violent pressure release can cause big cracks. Lastly, use eggs with thick shells.
Thanks, I’ll try it tomorrow 😉
Can’t wait to have “proper” brown eggs, I don’t make them much because of the temperature control hassle.
Let me know how it goes.
Went OK, 4 out of 6 eggs didn’t crack. Came out a bit light relatively but tasty, I’m not sure if my small pressure cooker is 15 psi. I’ll try later with the bigger one.
Thanks, cool stuff.
What if you removed the resistance and used a PID controller with the thermocouple set at 250. It seems like the resistor is the only limiter. #warrantiesareforbabies
Well, you could remove all the electronics and start fresh, but to use all the timers and what-not I think the best solution is to just hack the RTD.
Dave, in your Maillard-pipe-potato article you state that a pressure cooker at 15psi is at 257Â°F, but here you are targeting 250Â°F. What’s up with that?
Musta been a mistake. I looked up 15psig in the saturated steam tables and got 250F. 257F would be 19 psig. I’ll check the article. Also, I forget in that article how hot I took the pipe, but the first time I did that experiment was in my deep fryer at home.
Fascinating, albeit a bit dangerous – and you freely admit this. I went to look at the production of pressure cookers of Fissler in Germany and one thing they tested, was the strength of the pressure cooker top at 20 PSI, if it did not pass, this pressure test, it was melted back into stainless steel and had to start the trip through the factory again. My point being, I would also be concerned about the strength of the materials (top, etc.) of running a pressure cooker designed for 9PSI operating at 15. The danger is not over after you’ve done the modifications, so please steer clear of it while it is in operation!
In theory, even though it does not reach the same pressure (i.e. temperature) you should be able to get the same results cooking for more time – for example your stock experiments were (rightfully so) all at the same cooking time but differing pressures.
I must be on Cuisinart’s black list because no one has offered up an electric for me to eviscerate at home or online!
Keep the experiments coming, but just give your new hack a little extra room while it is under pressure – and thanks for stating “don’t try this at home!”
P.S. Instapot makes an electric with a stainless steel insert and Woflgang Puck one that reaches 15PSI… I’m just sayin’! ; )
I was initially concerned that the lid might not be designed to take the 15 psi safely, but in my tests, the safety vent on top didn’t release any steam (the pressure release on the Cuisinart doubles as a safety vent). My reasoning is: it would be a major problem if your safety didn’t engage before you exceeded the test pressure of the device.
While it is true that some recipes can just have their time extended when cooked at lower pressure, it is my deep belief that certain effects can’t be achieved just by extending time.
I don’t think you are on Cuisinart’s black list. I think I just got lucky –someone happened to go to a demo I did at the IACP.
Puck unit looks like a good deal at 115 bucks.
Can you recommend a pressure cooker? I am looking to buy one and would like your recommendation. Thanks!
Well, I’m not in the business of recommending products, maybe another commenter can. Are you looking stovetop or electric? What is your budget? How large a capacity?
Stovetop….large, for family of 4…..$200-250
I like the Kuhn Rikon for that.
If I were going to buy another pressure cooker, I would likely buy a B/R/K set with a 6 quart and a 3 quart. these pots are great looking, easy to use and made in Germany. You can use the small one to cook grains and the bigger one to cook another part of the meal. It’s my new favorite, and I have plenty of cookers.
I once had an issue with a Kuhn Rikon and hesitate to recommend them because of it but many people like theirs. Good luck. A pressure cooker is an amazing investment.
The Nesco electric pressure cooker can hit 15 psi without hacking. I don’t think it’s built much tougher than the Cuisinart though.
As Brandon asked, How did I not know about this website?
I have a Fagor Pressure cooker, and you’ve inspired me to try to use it in earnest this time.
Thanks for the informative blog.
“an oven set at 400 F, the inside of a piece of meat will never go above the sea-level boiling point of water ”
well, it certainly will but I don’t think it is called meat anymore 😉
Good to find your blog. Looking forward to more!
True nuff Mamakawama.
can you provide a closer picture on how to make the modification.
I would like to make modification too but need a closer picture.
Click on it twice (you have to go through the individual page first), native dimensions are 1000 pixels wide.
I made fabulous vegetable stock in my venting canner! As fresh as if it were straight from the garden.
Aren’t most of the most important items on your pressure cooker wish list best solved by simply using the Kuhn Rikon pressure cooker on a portable induction hob? Or, for that matter, by using the WAFCO pressure cooker on a portable induction hob with a cheap piece of carbon steel in between?
Technically, yes. But the no-scorch is real handy as is the auto temperature throttling and the auto shut-down.
I’m pretty tempted to pick up an electric cooker to save a burner and to up the efficiency (but honestly how much would I have to use it over our stovetop model in order for that to win out? Some time, I’d wager). I found a couple of EPCs online that do 15psi – there’s one from Nesco, a Wolfgang Puck-rebadge from someone, and this Cook’s Electric unit that promises to pressure smoke stuff, too.
As a complete aside – do you guys have any recommendations for a cool lunch spot? I’m coming into town for a couple of days next week and want to try somewhere new. I’m staying around 31st St, but I like to walk.
Hmm, anyone else with recommendations?
That temperature sensor was no RTD. You were dealing with a 10k thermistor that had a negative temperature coefficient (NTC). Thermistors are cheaper and easier to interface with but less accurate and are non-linear.
If I had to guess I would guess that your unit doesn’t sense pressure but rather if the lid is on or not. The purpose of this is likely so that your cooker knows NOT to shut off the burner at the temperature limit while the lid is off so that one can saute in it.
Also electric pressure cookers generally never reach steady state–there is no fancy PID algorithm. The initial pressure and temperature will be much significantly higher as there will be a heat dissipation delay from the heating element. Under normal operation the unit could go up to 15 psi and then down to bounce between 9 and 10. This isn’t all that different from a conventional rocker style pressure cooker that reaches 15 psi before the heat is lowered. By hacking it, you could be causing your cooker to go well in excess of 15 psi during the initial heating cycle before the unit starts maintaining the pressure around 15. You could be getting close to the pressure that will blow the safety seal–but if it doesn’t blow in the first half-hour its safe to say its not going to happen. If your unit has no switch to determine if the lid is on or not, this overheating period could be what you experienced when the unit didn’t shut off at 250. You were measuring temperature from the inside, it was measuring temperature through the surface of the inner container. There is a thermal boundary layer to consider.
You are correct.
Awesome post–I’ve been preaching the virtues of my cuisinart pressure cooker for years now, and was starting to wonder about its capabilities, as I had checked in w/cuisinart to find out what you did regarding the stock high/low psi settings. I’ll definitely plan to put my soldering iron to use shortly. Have you reassessed since reading Joel’s feedback vis a vis the stability of the temp/pressure? Just was wondering if that’s changed things as I look into acquiring some of the necessary parts.
The other, perhaps bigger, “aha” upon reading your post makes me think that this pressure cooker would be a great candidate for another modification, this time of the thermostat’s settings for “Keep Warm.” If I’m understanding things correctly, this same hack might enable one to control the temperature at that setting to maintain a lower temp a la sousvide supreme for at-home low-temp cooking, but without the much higher price tag. I suppose this particular unit might be subject to a larger spread, though perhaps that might be adjustable as well… Have any thoughts on this idea, or perhaps have tried it?
Thanks, and looking forward to some fun soldering!
I haven’t dorked with the unit since my initial mod –but it still works just fine! The coupling between the sensor and the pot isn’t accurate enough for low temperature work. You’d have to use one of the rice-cooker PID mods that is rolling around the net to get the accuracy you need. Once you did that you could theoretically make the unit do whatever you want.
Thank you for your post!
Did you notice a strong smell of hot electronics when you used it? Mine has that smell every time I use it(unmodded) but I can’t find anything wrong and it works perfectly.
PS: Just tried Hamine eggs because of this post. Delicious and intriguing.
I have heard of this problem but have not experienced it myself. Thanks for the feedback on the eggs.
Dave, have you seen any problem with the screw inside the Cuisinart lid oxidizing? Product pictures on amazon show what looks like a manufacturing material error. It’s probably not exactly safe to eat rust, is it?
I haven’t noticed any rust yet, but there is a screw that looks like it might be bright-coated instead of inox. I’ll keep an eye on it.
A randomish thought about pressure and cooking: one of the things Miss Vickie mentions on her site is the natural release method vs. the quick release method, and she notes that the quick release can make meats contract quickly and thereby not reabsorb their juices. This reminded me of your posts on using high pressure (and the quick release thereof) for flavor infusion and marination. Any thoughts on whether and how (and why) one might be able to combine these two techniques?
Hmmm. I’m not sure what she means by contract. I know quick release blows things apart and causes them to give off moisture (maybe that is what she means), In which case it would act like a much hotter, not as violent form of the infusion trick.
How much was the warranty you voided?
Ha Ha. I guess just the price of the machine (which was free).
I was just watching the Science and Cooking lecture with you and Harold and I was very interesting about how elevating temperature in a pressure cooker destroys aroma molecules at a fast speed, which makes me wonder: is it possible to destroy those compounds without heat, therefore retaining original texture?
Dunno Carlos, I hadn’t thought about it. Yo’d need to find some food grade way of chemically altering them without making the stuff taste bad. Sounds like a hard problem.
You’re a genius Dave. Luckily, I found your site and wow, very interesting. I got to follow your path, and I’m sure I’ll be learning a lot more from you. I was intrigued by those eggs, got to try to do this as well.
Your comments on 15 psi being a critical number are interesting. I wonder how much of a problem it poses for those of us cooking at altitude (in my case, 6000 feet). So that means that inside our Kuhn Rikon pressure cooker we are only at 26.8 psia instead of 29.7. Which means we are cooking at about 244 F instead of 250 F if we are at the nominal 15 psig.
Is that 6 degree difference critical for your garlic and onion recipes you mentioned? It seems to work fine for most of my applications, including the jus and stocks from MC, and the tomato (pizza/marinara) sauce I adapted from Blumenthal.
One way I might be able to “cheat” is to try to bring the Kuhn Rikon all the way up to pressure where the secondary safety valve kicks in and starts venting some steam, or as close to this point as I can get without going over. That valve goes off at 17.4 psig, which means we are cooking at 29.2 psia, which should mean we are pretty close to that 250 F mark.
Interesting David G,
I have thought about this before. you are correct. I haven’t actually run side by sides with all of the pressures with onions. My detailed pressure side by sides have been with stock. I routinely blast my KR up to just before the vent point. That would work.
Tremendous ideas here. Can I seal my meat into a sous vide bag to minimize release of flavor compounds. It seems like the pressure cooker is like an atomizer on my stove right now. I know that cooking of products can be done in Mason jars, but fitting a pork butt into one of those wouldn’t be an easy task. I would assume a ziploc would melt, but who know?
Ah, No you cannot unfortunately. To cook in a bag in a pressure cooker you need what is known as a “retort bag.” Ziplocs will definitely melt in a PC. I don’t even use them for boiling water. I’m assuming you have a venting style cooker. What brand? Some can be Jerry rigged into ventless by adding extra weight, etc –the problem is you then have no measurement of the internal pressure. That is one of the main reasons I love Kuhn Rikon.
A cheap-o 6 qt. Stainless Presto. And I’m assuming that a retort-bag could only be sealed w/ a chamber sealer.
I think a regular heat sealer will seal a retort bag, but you’d have to seal for a longer time. Don’t quote me though, I haven’t done it personally.
Saw a recent demo of yours in Cambridge with Harold McGee and enjoyed it thoroughly… I was then prompted by you to buy a pressure-cooker, and *then* was just saddened to note that it only reached 10 psi. (It’s the Cuisinart.) Googling around a little, I now see that (a) it actually even only reaches about 9, as you say, and (b) that *you* of all people have hacked it!! How amusing.
Now for my super-exciting question: do you know the power rating of your variable potentiometer?
Is this correct that
P = VÂ² / R, so with 120V and 1270 ohms we’d need a rating of at least 11.3 watts?
Also wondering: how’s your unit been holding up in general? I guess since you haven’t reported any deaths that the seal is still good?
Thanks for all the inspiration.
(I guess the voltage in the temp-sensing circuit is actually way less?)
Yes. There is minimal current running through the sensing line. I forget what the voltage is, but it is small as well.
My final comment (sorry for all the postings!) : Have you noticed whether your mod influences the ‘warm’, ‘sautÃ©’, or ‘browning’ temperatures? For example, maybe the ‘warm’ setting after cooking is really still quite hot, and may continue to actively cook the food?
I’m assuming I’m shifting all the temperatures up by a bit. I never trust warm temperatures anyways, however, they are almost always in the “continue to cook” range. It would be interesting to measure, however. Someday I’m hoping Cuisinart will just fix their own machine!
Cool, thanks for your helpful replies. I’m thinking about throwing a little switch into the resistor circuit too, so I can shift into hypercook 15psi mode whenever I want 🙂
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