Stock in a Pressure Cooker

[jackal10]

http://www.guardian.co.uk/weekend/story/0,...1141521,00.html

[Jinmyo]

Hm. HB says:

A final advantage is that the pressure keeps the liquid inside the cooker much less turbulent, which helps to keep the stock that much clearer even before you clarify it (unlike the traditional method, which renders all sorts of impurities).

But this is my primary objection: The stuff has not simmered gently but has been at too high a heat and brutalized.

However it has been a very long time since I've used a pressure cooker at all.

[Bruce Cole]

On the other hand, you don't (theoretically) lose a lot of the flavors, since there is no evaporation. This same theory applies to sous vide cooking, where you cook ingredients sealed in an airtight bag, and in the process, retain all the vital juices and aromas.

Sounds good in theory anyways...

Besides, if you need stock in 30 minutes, for a risotto, lets say, the pressure cooker is the way to go, especially for a simple vegetable based stock.

[Dave the Cook]

I'm sure this will make a very decent broth -- the little booklet that comes with your pressure cooker tells you how to do it. As for stock, maybe.

Some things that happen while the stock simmers are at least as time-dependent as they are temperature dependent -- the conversion of collagen to gelatin being the first that comes to mind. This is not to say that pressure won't enhance or accelerate the conversion, but Blumenthal doesn't say anything about it, and that makes me wonder.

Bruce makes a good point, but if speed is what you're after, Kafka's microwave technique does a decent job in just five to ten minutes.

[tan319]

But isn't Heston talking about intensifying flavor?

As for the gelatin question, maybe that process is intact thru the temperature being reached.

If you could pressure cook a lamb shank for instance, so that the meat falls off the bone, I would think that this method could still give you the gel.

Anyways, cool idea.

I surprised someone hasn't thought of it before.

[Dave the Cook]

yes, he's after intensity, which normally you would get through reduction. I admit to being intrigued by this:

. . . 140C, which is round about the point when those lovely meaty flavours in the stock really begin to develop . . .

I've never heard this before, and I wonder what it means, exactly.

The problem with gelatin is that collagen doesn't convert instantly, it takes a while for complete rendering. I know that the few pressure-cooked pot roasts I've had lacked the succulent mouthfeel of a two- or three-hour braise for just this reason. Maybe under more liquid conditions, the pressure speeds up conversion -- or maybe what Blumenthal is calling stock is not what I would call stock.

Having said all that, if I had a pressure cooker, I'd try it for sure.

[ExtraMSG]

Here's where I need a personal chemist.

My understanding is that you want to melt the collagen and other bits from the bones and connective tissues without using a temperature that is so high that it coagulates the bits in the bones instead.

My understanding of a pressure cooker is that it lets the water reach about 250 degrees instead of 212. Even a boil will not merely let the bits melt into the stock, I thought.

However, that said, the Iron Chefs use pressure cookers for stocks.

[Katherine]

Having said all that, if I had a pressure cooker, I'd try it for sure.

This is what it's going to take. All this talk about theory can only be settled by real-life testing.

My pressure cooker is only 4 quarts in size, so it's going to have to be someone else. That and the fact that I'm not a stock person.

[Dave the Cook]

Having said all that, if I had a pressure cooker, I'd try it for sure.

This is what it's going to take. All this talk about theory can only be settled by real-life testing.

My pressure cooker is only 4 quarts in size, so it's going to have to be someone else. That and the fact that I'm not a stock person.

Right. From a practical standpoint, you need one of these, and unless you do a lot of canning, you probably don't have one. I can't imagine what kind of cooker you'd need for restaurant-sized volumes of stock. But the idea could be tested in a smaller vessel. Are you sure we can't turn you into a temporary stock person?

[Katherine]

Having said all that, if I had a pressure cooker, I'd try it for sure.

This is what it's going to take. All this talk about theory can only be settled by real-life testing.

My pressure cooker is only 4 quarts in size, so it's going to have to be someone else. That and the fact that I'm not a stock person.

Right. From a practical standpoint, you need one of these, and unless you do a lot of canning, you probably don't have one. I can't imagine what kind of cooker you'd need for restaurant-sized volumes of stock. But the idea could be tested in a smaller vessel. Are you sure we can't turn you into a temporary stock person?

Jon: Microwave Gourmet.

Actually, when I say I'm "not a stock person", what I mean is that I don't really like Western-style stock, with the infused vegetable flavors, bones, etc, and I usually make chicken broth. So even if I did make stock, I'm not sure if I would be a good one to run a taste test on the finished product, having tasted little or none of it.

I could test two batches of chicken broth side-by-side, but I work two jobs, and after caucuses today, I have to go to work. Plus, my freezer is packed full of chicken and turkey broth already.

Edit: I have got to start proofreading my posts.

Edited February 8, 2004 by Katherine (log)

[Dave the Cook]

I could test two batches of chicken broth side-by-side, but I work two jobs, and after caucuses today, I have to go to work. Plus, my freezer is packed full of chicken and turkey broth already.

What's your point?

[tan319]

However, that said, the Iron Chefs use pressure cookers for stocks.

That makes me consider it a good idea even more...

[Katherine]

I could test two batches of chicken broth side-by-side, but I work two jobs, and after caucuses today, I have to go to work. Plus, my freezer is packed full of chicken and turkey broth already.

What's your point?

I give up. I'll give it a try. It's fate. But it's gotta be chicken broth for me.

I went to Walmart and picked up a 10# bag of chicken leg quarters. I decided to start 3 batches, each of merely 1lb 12oz of chicken leg quarters in 1 quart of cold water:

• Pressure cooker batch-30 minutes at high pressure
  
• Stovetop batch-bring to a boil, skim, then simmer gently for 1 hour
  
• Le Creuset in oven batch-leave in the oven at 200º until I get home from work at 9:45 tonight.
  

What I'll do is strain each batch after it cools a bit, then chill, defat, and compare. I'll also be able to compare the eating quality of the chicken meat that will be a by-product of this process. But since the oven batch is not going to be ready to use til tomorrow morning, and I may be working tomorrow morning (don't know yet), the final test may be delayed until I have a free morning.

If this works, it will be very interesting, because it may mean that we've all been operating on an untested incorrect assumption all this time. (C'mon, folks, how often do you really run two batches side by side to check some detail?)

But I would recommend that anyone who wants to make stock this way for home use should invest in a significantly larger pressure cooker than mine. I believe the programmable ones do come in larger sizes, or at least I did see 8 qt and 12 qt at one time.

Edited February 8, 2004 by Katherine (log)

[mongo_jones]

On the other hand, you don't (theoretically) lose a lot of the flavors, since there is no evaporation.

i'm assuming the kinds of pressure-cookers being talked about here are different from my stone-age pressure cooker from india--which releases a little to a lot of steam depending on heat.

[slkinsey]

There is also the issue that simmering a stock with the lid off supposedly allows for the evaporation of certain undesirable volatiles that would remain behind in covered stock. Aren't covered stocks supposed to have a "vegetal" taste?

[Katherine]

On the other hand, you don't (theoretically) lose a lot of the flavors, since there is no evaporation.

i'm assuming the kinds of pressure-cookers being talked about here are different from my stone-age pressure cooker from india--which releases a little to a lot of steam depending on heat.

My former boss tried to tell me about pressure cookers in India, but since he didn't know anything about cooking, and his English wasn't all that good either, very little communication occurred.

The old-fashioned pressure cookers I used to use had a steam port on top, with a rocker weight you set on it. Clamp on the cover air tight, put on the weight, and put the pot on the fire. When the steam discharge becomes so great that the weight begins rocking back and forth, you turn down the heat just enough to maintain that pressure. You want to make sure the pressure doesn't get too high, which could be dangerous. A pressure canner has a pressure gauge on top so you can read the pressure for safe canning.

The modern one I have maintains its heat itself, and has two pressure settings, low and high. I use high for beans, and low for rice.

[Katherine]

There is also the issue that simmering a stock with the lid off supposedly allows for the evaporation of certain undesirable volatiles that would remain behind in covered stock. Aren't covered stocks supposed to have a "vegetal" taste?

Your mission, SLK, is to test this and see if it is true. Please report back.

[jackal10]

I use a pressure cooker for stock when I'm in a hurry. My Tefal pans have a pressure cooker lid option, so I can cook about 6 litres at a time.

Its OK, but somehow different to a traditional stock: maybe fresher and more aromatic, but thinner and less unctious. I guess that indeed theere is less conversion of the collagen. You do get quite a lot of volatiles escaping via the vent.

I've never just chucked in a couple of leaves of gelatine, but I don't see why not..

[ExtraMSG]

I imagine you'd be a lot better off roasting the bones nicely first. Less albumen/scum production, I think, and more flavor. Although, then you're getting a brown stock out of it. But I'm one who thinks there's no point in anything else.

[Katherine]

Results are in. Check them here.

[jackal10]

Splendid work! You have made an important contribution to the world's knowledge and chicken soup induced happiness!

Overnight in the oven wins! Especially if you boil it down by half...

[Dave the Cook]

Many thanks, Katherine. This is a great contribution. I'm thinking that I will test your oven method against the results I reported here.

[Dave the Cook]

Results are in. Check them here.

For the sake of convenience, here are Katherine's data and notes:

Since I had by this time run out to Walmart and purchased a ten pound bag of chicken leg quarters, I decided to test as many parameters as possible. Besides making a batch of pressure cooker chicken broth and a stovetop batch, I decided to also make a batch in a french oven, baking it for a longer period of time at a lower temperature. Later, before I had the opportunity to compare the resulting broths, I decided to make a french oven batch where the chicken was pre-roasted, too. The meat and bones would be strained out and examined, the broth would be chilled, defatted, examined, and tasted to provide observations.

I weighed out chicken, 1 lb. 12 oz. per batch, and covered the first three batches with 1 qt. of cold water. I started the pressure cooker, set at 30 minutes, put the second pot on the fire to simmer, and put the french oven in the oven at 210ºF.

When the pressure cooker stopped and the pressure had gone down, I poured the contents through a strainer into a bowl, and put it to refrigerate. After 1 hour of boiling, I did the same thing with the stovetop batch. The french oven batch came out of the oven after about 6 hours, was strained and chilled.

Next I dismembered the same quantity of chicken and baked it at 400ºF in a cazuela until well browned. I put the chicken into the french oven, rinsed out the cazuela with warm water, scraping to make sure I had all the tasty residue, and poured this into the french oven too. The french oven went into the oven for about 7 hours at this point.

Days later, I finally had a day off from work to evaluate my results, which I have summarized in the table below.

I tested the clarity of the broth by pouring an inch into each of four clear glass bowls, and setting them on top of the notecards I was using to record my data on. How well I could read my writing through the liquid was what I was looking for.

Data Summary Table

<table cellpadding="2" cellspacing="2" border="1"

style="text-align: left; width: 85%;">

  <tbody>

    <tr>

      <td style="vertical-align: top;"><br>

      </td>

      <td style="vertical-align: top;">Test 1<br>

      </td>

      <td style="vertical-align: top;">Test 2<br>

      </td>

      <td style="vertical-align: top;">Test 3<br>

      </td>

      <td style="vertical-align: top;">Test 4<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Cooking method<br>

      </td>

      <td style="vertical-align: top;">Pressure cook for 30 minutes<br>

      </td>

      <td style="vertical-align: top;">Gently simmer in a pot on the

stove<br>

      </td>

      <td style="vertical-align: top;">Bake in a french oven for 6

hours at 210º<br>

      </td>

      <td style="vertical-align: top;">Bake chicken pieces until brown,

then place in french oven and bake for 7 hours at 210º, rinsing out

and scraping the baking dish to retain drippings<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Fat layer<br>

      </td>

      <td style="vertical-align: top;">More fat<br>

      </td>

      <td style="vertical-align: top;">Less fat<br>

      </td>

      <td style="vertical-align: top;">Less fat<br>

      </td>

      <td style="vertical-align: top;">Lots of fat<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Gelatinization<br>

      </td>

      <td style="vertical-align: top;">Less<br>

      </td>

      <td style="vertical-align: top;">More<br>

      </td>

      <td style="vertical-align: top;">More<br>

      </td>

      <td style="vertical-align: top;">Most<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Color<br>

      </td>

      <td style="vertical-align: top;">Off-white<br>

      </td>

      <td style="vertical-align: top;">Off-white<br>

      </td>

      <td style="vertical-align: top;">Pale golden<br>

      </td>

      <td style="vertical-align: top;">Deeper golden<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Clarity<br>

      </td>

      <td style="vertical-align: top;">Slightly translucent<br>

      </td>

      <td style="vertical-align: top;">Worst<br>

      </td>

      <td style="vertical-align: top;">Clear<br>

      </td>

      <td style="vertical-align: top;">Clear<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Taste<br>

      </td>

      <td style="vertical-align: top;">Boiled chicken, fresh taste<br>

      </td>

      <td style="vertical-align: top;">Fresh taste, but more flavor

notes<br>

      </td>

      <td style="vertical-align: top;">Less "fresh boiled" taste, more

mellow or long-cooked taste<br>

      </td>

      <td style="vertical-align: top;">Same as unroasted Le Creuset<br>

      </td>

    </tr>

    <tr>

      <td style="vertical-align: top;">Meat quality<br>

      </td>

      <td style="vertical-align: top;">Mushy, tasteless mess<br>

      </td>

      <td style="vertical-align: top;">Seriously overcooked, but not

broken down. Tasteless<br>

      </td>

      <td style="vertical-align: top;">Broken down, tasteless<br>

      </td>

      <td style="vertical-align: top;">Tasty, usable.<br>

      </td>

    </tr>

  </tbody>

</table>

Conclusions

The stovetop broth was superior in taste to the pressure cooker broth, so unless you're an Iron Chef with extreme time limitations, the cost of equipment and extra cleanup would probably not be worth it. I know I'm not going to be investing in a large pressure cooker to make stock in.

Both french oven broths were golden and attractively clear, as chicken soup ought to be, though not as sparklingly clear as if they had been clarified.

The big surprise was that there was no difference between the two french oven batches, the one that had been pre-roasted and the one that had not been. So if you're throwing away the chicken after making stock or broth, don't bother to roast it, but if you want to eat the chicken, roast it first, and it'll still be usable.

One last observation is that all of these still were a little weak, so I'm boiling down the leftovers as I write this.

Edit: this data was posted with Katherine's permission.

[slkinsey]

Since I am about to purchase a fairly powerful meat grinder, I plan to experiment with grinding all the ingredients finely (especially the bones) before adding the water and proceeding with the stock. My guess is that the flavor extraction will be faster and the gelatin extraction will be much greater.

[jackal10]

This week he deep fries and liquidises the ingredients (he quotes quail) first....

http://www.guardian.co.uk/weekend/story/0,...1146720,00.html

Liquidising I understand, except for anything bigger than quail I find it gives too much "bone-taint" falvour.

Deep frying I'm more doubtful about. HB says it doesn't lose so much flavour as roasting/deglazing, but I would have thought the flavour just dissolved in the oil instead. However, he is a three-star chef and I am not.