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Unvented Pressure Cookers (Kuhn Rikon, Fissler) and PSI control

simplycumin

By simplycumin
in Kitchen Consumer

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simplycumin

simplycumin

Posted
Posted

Hi all,

My experience with pressure cookers is with Presto and a Fagor Duo when I lived in Australia. Both vent steam to keep the internal pressure at a desired level.

Unvented cookers like KR and Fissler allow a range of pressures. As I understand it, they only vent when the pressure passes a certain maximum threshold.

I have two questions, then:

1. Doesn't the variability of pressures make it harder to time dishes? For example, if I want to steam eggs, which are quite sensitive to time+PSI, one time it might be 1 ring of pressure and the next time 1.2 rings.

2. I'm actually mainly interested in the Fissler Vitaquick. The intended use is an electric stove, and the Vitaquick does not appear to have a pressure "selector"; you simply lower the heat earlier when the first ring appears to get lower pressure setting. Given the long lag in the response of the electric stove to heat being lowered, will it be difficult to achieve "low" pressure cooking on the Vitaquick?

Franci

Franci

Posted
Posted

My guess is yes!

I have two Pressure cookers, vented (lagostina) and unvented (kuhn rikon), and I've been using until August on an induction hob. Even with induction I have a problem lowering the pressure quickly enough for food that requires a quick cooking and a lower pressure, vegetables for example. They come up much better in my old vented lagostina. But kuhn rikon is unbeatable for other stuff like stock, risotto, or for caramelizing some fruit or vegetables.

eG Foodblog: Franci (2012) From heirloom tomatoes to zucchini blossoms

Dolci di Franci

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dcarch

dcarch

Posted
Posted

Pressure has nothing to do with cooking.

Temperature does.

Use a non-contact remote thermometer to check temperature when you vary the pressure.

dcarch

dcarch

dcarch

Posted
Posted

Franci, let me put it this way:

If you use compressed air to increase pressure in your pressure cooker, but use no fire to change temperature, it will make no difference to the food, regardless how high the pressure is.

When you have fire to increase pressure, it allows the boiling point of water to get higher, therefore higher temperature can be achieved.

dcarch

pazzaglia

pazzaglia

Posted
Posted (edited)

Thanks for letting me know about this topic and giving me an opportunity to answer.

Hi all,

My experience with pressure cookers is with Presto and a Fagor Duo when I lived in Australia. Both vent steam to keep the internal pressure at a desired level.

Unvented cookers like KR and Fissler allow a range of pressures. As I understand it, they only vent when the pressure passes a certain maximum threshold.

I have two questions, then:

1. Doesn't the variability of pressures make it harder to time dishes? For example, if I want to steam eggs, which are quite sensitive to time+PSI, one time it might be 1 ring of pressure and the next time 1.2 rings.

From your question, I see that venting and non-venting cookers are getting mixed-up with selector-type and rod-type pressure indicators. So let me explain a bit..

Venting vs. Non-Venting Pressure Cookers

A venting cooker operates with a weighted valve that either lifts up or jiggles to release pressure when the pressure inside the pressure cooker is higher than the weight. This type of cooker has a much higher evaporation rate than non-venting cooker, needs more energy to stay at pressure and the food inside is jostled whenever the cooker vents (releases pressure) due to constant sharp drops of pressure. A good example of this type of cooker is the Presto you saw, or Fraci’s Lagostina.

A non-venting cooker operates with a spring valve that is calibrated to resist up to a maximum pressure. When the pressure goes beyond what the spring’s resistance, it yields and cooker begins to release pressure. The pressure is regulated in these cookers by heat. Less heat, makes less steam, which makes less pressure. This type of cooker has a very low evaporation rate (about a tablespoon or so every 10 minutes), needs very little energy to maintain pressure and once the fire/heat/induction are adjusted to the precise amount this type of cooker needs to maintain pressure, the food in the cooker remains completely still (no small boils) and cooks at the same continuous temperature the entire time.

An interesting aside about electric pressure cookers. Even though they do not vent, internally they have similar temperature swings as venting cooker because the heat source (electrical coil) is constantly turning on and off to maintain a certain temperature.

Rod vs. Selector Pressure Indicators

The pressure on spring-valve non venting cookers can be indicated with either a rod that raises progressively out of the cooker (with marks to indicate high and low pressure) or a selector switch that works in concert with a pressure signal to indicate whether the selected pressure is reached.

Between the two, the rod is more accurate because it’s very easy to see the progress. Although the selectors give a nice satisfactory “click” (which I like, too) there is actually some play with the range of pressures for each selection. An excellent example is the Fagor Duo – where you select high or low pressure but that pressure has not actually been reached until a small wift of vapor comes out of the valve and the little yellow pressure signal is completely solid.

The most accurate of all pressure indicators is a calibrated gauge with a needle to show the exact internal pressure. Unfortunately, this type of pressure signal is not available for any pressure cookers designed for home use!

2. I'm actually mainly interested in the Fissler Vitaquick. The intended use is an electric stove, and the Vitaquick does not appear to have a pressure "selector"; you simply lower the heat earlier when the first ring appears to get lower pressure setting. Given the long lag in the response of the electric stove to heat being lowered, will it be difficult to achieve "low" pressure cooking on the Vitaquick?

Since your focus is on the Vitaquick, you should know that Fissler makes a different Vitaquick for the U.S. The Euro model operates at 11 .6psi (80kpa) and the American model operates at 8.7psi (60kpa) at the high pressure setting - the US model has the letters "US" engraved in the metal on the lid just near the lip and to the right of where the handle connects.

As mentioned earlier, by ojisan, when using a pressure cooker on an electric cook top. Bring the pressure cooker up to high pressure on a burner at high heat, while pre-heating a smaller burner at low heat. When the cooker reaches pressure delicately move it over to the lower heat burner and turn off the higher heat one.

Ciao,

L

Edited by pazzaglia (log)

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

pazzaglia

pazzaglia

Posted
Posted (edited)

My guess is yes!

I have two Pressure cookers, vented (lagostina) and unvented (kuhn rikon), and I've been using until August on an induction hob. Even with induction I have a problem lowering the pressure quickly enough for food that requires a quick cooking and a lower pressure, vegetables for example. They come up much better in my old vented lagostina. But kuhn rikon is unbeatable for other stuff like stock, risotto, or for caramelizing some fruit or vegetables.

Franci,

You should bring your pressure cookers up to pressure on medium heat using induction - they should take the same time to come up to pressure as they used to on your other cook top (probably 5 or 6 minutes for the Lagostina and 10 minutes for the kuhn) on induction in order for them to properly expel all of the air while they're building pressure.

I'm working on an article about pressure cooking on induction with more details.

Ciao,

L

P.S. Yes, your two cookers have different operating pressures (temperatures). Likely your Lagostina is operating at 9 or 10 psi (check your manual for anything that says kpa, bar or psi) while you're Kuhn Rikon operates at 15psi (a little after the second red ring comes out).

Edited by pazzaglia (log)

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

  • 2 weeks later...
Unpopular Poet

Unpopular Poet

Posted
Posted
Since your focus is on the Vitaquick, you should know that Fissler makes a different Vitaquick for the U.S. The Euro model operates at 11 .6psi (80kpa) and the American model operates at 8.7psi (60kpa) at the high pressure setting - the US model has the letters "US" engraved in the metal on the lid just near the lip and to the right of where the handle connects.

Thanks for all of the helpful information -- My question is whether, being a US buyer, you would suggest a different model (say a Kuhn Rikon) over the Fissler, because of the difference between the Euro and US models? I have an old Presto pressure cooker that just doesn't get it done anymore -- I need something new -- and I am interested in both the Kuhn Rikon and Fissler. I also have a massive one with a gauge, but that is pretty much worthless in 99% of all of my uses. More useful for large canning projects than actually pressure cooking.

Thanks for all of the insights --

Dan

Shalmanese

Shalmanese

Posted
Posted

Franci, let me put it this way:

If you use compressed air to increase pressure in your pressure cooker, but use no fire to change temperature, it will make no difference to the food, regardless how high the pressure is.

When you have fire to increase pressure, it allows the boiling point of water to get higher, therefore higher temperature can be achieved.

dcarch

Experiements with ISI canisters show that increased pressure without increasing temperature can result in faster marination/infusion times.

PS: I am a guy.

lindag

lindag

Posted
Posted

My question is whether, being a US buyer, you would suggest a different model (say a Kuhn Rikon) over the Fissler, because of the difference between the Euro and US models?

Dan, I have two Fisslers and four Kuhn Rikons. IMO there is absolutely no contest. While the K-R are quite nice, they're nowhere near as high quality as the Fisslers.

lindag

lindag

Posted
Posted

Poet,

Yes, the US model Fisslers. I love mine and if I could I'd trade the K-R's for them in a minute. And that's not to say the K-R's aren't really great PCs; it's just that Fissler models are so much better. The big difference I see is in the disc base - the K-Rs don't cover the entire bottom of the pan/pot, so there's scorching sometimes. And the Fisslers are heavier overall.

Earthlark

Earthlark

Posted
Posted

Hey, Linda,

Since the Vitaquick only cooks at 8.7 psi on setting 2 (and 4.4 psi setting 1), I'm curious if you usually lengthen the cooking time when following traditional 15 psi recipes. I have a large Vitaquick quatro set sitting here and, now, a WMF Perfect Plus set on the way because I wasn't terribly excited to learn of the Vitaquick's lower pressures. I guess I'll figure out which makes me smile more once the WMF gets here next week...

takadi

takadi

Posted
Posted (edited)

I got a used 7 L Kuhn Rikon pressure cooker (the one with the long handle) from ebay, and knowing very little about Kuhn Rikon in general, I need to know if this guy ripped me off or not.

First, when I tried cooking stock with it for the first time today, it sputtered and vented quite a lot when heating it up. The instruction manual says that when its coming up to pressure it should push out air then the stem should rise and seal it. So I'm not sure if this is what's supposed to happen. It took quite a long time for the stem to even rise and seal up (some 15-20 minutes on medium heat) and I had to help it up a little by pulling up on it. When it reached the first red mark, the venting and sputtering died down, but it was still hissing. I thought one of the main features of kuhn rikon was that it was enclosed and didn't vent. Do Kuhn Rikons still vent but just vent *less*? Or do I have a defective valve? I bought a new SI (UL) valve and a new stem spring just in case and I'm going to test out to see if it makes any difference.

Also, upon doing a little research and shopping for a new SI valve, I noticed that although I have a 3344 model, the main valve I have right now does not match the model.

http://www.pleasanthillgrain.com/replacement_parts_kuhn_rikon_pressure_cookers.aspx

According to that site, the current valve I have is for the older models. Also, the instruction manual that came with it shows pictures of the older valve model...which makes me suspect he either switched up the parts and sold me old parts, or he sold me a very old model with a new valve housing...or that website could be wrong.

Anyway, I digress...my other question is, is there any performance difference between the old valve and the new valve? If so I'm wondering if this is the reason it's not working as well as it should. Perhaps the valve stem is for the newer model and doesn't match the older valve I have?

Edited by takadi (log)
pazzaglia

pazzaglia

Posted
Posted

You should contact Kuhn Rikon to ask them about the different SI valve models and whether they are interchangeable. My educated guess says yes. They just snap into a hole in the lid - as long as the hole is the same size it should not matter what SI valve you have in what Kuhn Rikon model lid. There can be variations in the design and color, too. My new Kuhn Rikon came with a gray silicone stopper to the valve, but the replacement one was blue.

What kind of cook top are you using? The Kuhn Rikon instructions say to "turn the heat source up to full power" for it to reach pressure - medium heat should only be used to build pressure on induction (http://bit.ly/1bgMUA8).

Pressure cookers take an average of 10 minutes to build to full pressure - this can take longer if the cooker is very full. If you were making stock, I imagine the cooker was 2/3 full and since you used medium heat to bring it to pressure it would make sense that it would take 15-20 minutes to reach pressure.

There is a low hiss when Kuhn Rikon is at pressure, this is completely normal. Non-venting is a bit of a misnomer because all non-venting cookers vent a little bit. What it really means is that a non-venting cooker does not regulate pressure by venting (like the older weight-modified valves) instead, pressure is regulated by turning down the heat (venting cookers need medium heat to maintain pressure while non-venting cookers need low or very low heat).

Ciao,

L

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

takadi

takadi

Posted
Posted (edited)

Thanks for the reply. I actually read through the entire pressure cooker thread after posting this and it was very educational, especially your posts. It seems that some hissing while under pressure is normal, which is sort of disappointing to me since I expected practically zero venting and smells (smells to me indicate escaping of volatiles and therefore flavor). I have no comparison but it just seems like it's hissing more than it should be. I will be receiving the new safety valve tonight, so I will rule out whether it will make a difference. I didn't remove the valve housing and check (didn't know you could remove it until after cooking was done) but most of the steam venting off during pressurization was coming from a small area, which makes me suspect that the safety valve is faulty...if it was coming from the main valve, I think it would have been coming out from all directions, yes?

I think I saw your post that Fisslers apparently have the least venting of all "non-venting" pressure cookers? Unfortunately, they are the most expensive out there.

Referring to the interchangeability of the valves, I was actually referring to the main socket valve, not the safety valve. According to the site, there seems to be an old model and a new model. I have a supposed new model, a 3344, but the valve it came with is an old model. I wasn't sure if there was a performance difference between the old and new model or if it was just cosmetic and the two valves are interchangeable along with their indicator stems. If it's the former, I'm wondering if it is hindering the performance of the cooker and not the safety valve.

Edited by takadi (log)
takadi

takadi

Posted
Posted

Okay I got the new safety valve today and tested it out with a couple inches of water. While the safety valve did contribute to the hissing and venting while heating up, it was mostly a stiff spring and a leaky o ring that was the cause. When it got to pressure, the o ring continued to spurt and vent. I tightened the valve and while it helped quite a bit, although it's relatively quiet at the first mark, at the second mark it still hisses considerably. I'll probably try getting a new o-ring as well, luckily those are much cheaper than the safety valve

  • 8 months later...
takadi

takadi

Posted
Posted

The hissing at 15 psi has gotten much worse and I have no idea what's causing it. Before, I could jiggle the indicator a bit and the hissing would die down but now it continually hisses just like before. This is with a safety valve and valve gasket replaced last year. I posted a video to show how it sounds like. The air seems to be coming from the holes in the valve rather than through the gasket where the valve meets the lid or from the safety valve (tested with a metal spoon). Is this supposed to happen? I can feel the steam coming through them and I can smell the aromas escaping from them. It makes the house smell good but I thought the point of an unvented pressure cooker was to keep the aromas inside. 

 

 

https://www.youtube.com/watch?v=e6VLcMk9qIc&feature=youtu.be

Chris Hennes

Chris Hennes

Posted
Posted

I have basically the same model you do, and mine is dead silent with no appreciable leakage at pressures all the way up past the second bar and into the overpressure zone (but below the safety vent limit), so I'd say there's still something wrong with your cooker. I'd go with pazzaglia's advice above and try to get hold of someone at KR to talk to them about it.

Chris Hennes
Director of Operations
chennes@egullet.org

takadi

takadi

Posted
Posted (edited)

 I was trying to provide a reference point for how the hissing sounds like. It hisses despite me fiddling around with it anyway, as I tried to illustrate at the end of the video. I recorded a video without jiggling it and it was difficult to distinguish the hissing as ambient noise.  Two, I would do this before and as I said, the hissing would die down a little, not completely. However, doing it this time did not result in anything.  

 

Perhaps jiggling it before was a placebo effect and only resulted in an aesthetic difference in venting, not anything substantial. I definitely know it vented before because it would fill the house with aromas quite quickly. 

 

 

 

I have basically the same model you do, and mine is dead silent with no appreciable leakage at pressures all the way up past the second bar and into the overpressure zone (but below the safety vent limit), so I'd say there's still something wrong with your cooker. I'd go with pazzaglia's advice above and try to get hold of someone at KR to talk to them about it.

 

Unfortunately I bought this used off of ebay. Would Kuhn RIkon still work with me to get this fixed? I have no idea what could cause this unless this is what it's supposed to sound like, which obviously you say it should not.  The pressure valve doesn't have many moving parts... I have replaced the gasket, the safety valve, and the spring, so the only parts left are the indicator stem, the valve itself, and the metal fastener ring. The parts that are left, including the lid itself, are solid metal, so I don't understand what could go wrong where the indicator stem was unable to seal the valve, unless I'm missing a gasket.

 

Also, I noticed that when doing a natural release, steam would randomly spit out of the safety valve as it was about to fully release pressure (indicator valve still popped up but with the lowest psi notch already below)

Edited by takadi (log)
pazzaglia

pazzaglia

Posted
Posted (edited)

takadi,

 

I don't expect your cooker's warranty is valid anymore but I'm sure that Kuhn Rikon will trouble-shoot with you and find the issue.  Personally, I did not see (or hear) any operation out of the norm in the video you just posted.

 

You can shoot KR a message here:
http://us.kuhnrikon.com/us/en/company/contact.html

 

What intrigues me is that you say that it didn't hiss before and it does now.  Can you share what kind of cooktop you are using with your pressure cooker and what heat settings you use to reach and maintain pressure? Also, how do you clean the lid?  Dishwasher? Bleach? ...?

 

Ciao,

 

L

Edited by pazzaglia (log)

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

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