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KaffirLime

Sous Vide: Recipes, Techniques & Equipment (Part 4)

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When the pressure outside the bag and inside the bag are equal - the bag wouldn't collapse ( just like when gravity and lift are equal an object would be in flight), when the pressure inside the bag is approaching zero - the bag inevitable collapses (it's not cooking - it's physics, really). Would you agree with me on that?

The bag only collapses because there is a temporary pressure disequilibrium. Once the bag collapses (which happens almost instantly), the inside and outside of the bag are in pressure equilibrium. This is only relevant with respect to a chamber sealer. For edge-sealer type machines, the inside and outside are always at pressure equilibrium.

Perhaps these graphics can explain.

Here is a piece of meat inside of a bag. The bag is full of air. You can see by the air molecules that the inside and outside of the bag are at pressure equilibrium and the meat is under regular atmospheric pressure.

gallery_8505_416_36862.jpg

Now we have sucked most of the air out of the bag in a chamber vacuum and sealed the bag. The graphic below shows the conditions right after the chamber is opened. As you can see, the inside of the bag is at lower pressure than the outside of the bag (illustrated by showing that there are far fewer air molecules per square inch inside the bag compared to outside the bag). There is pressure disequilibrium, and the meat is not under regular atmospheric pressure (note that the pressure arrow is not touching the meat).

gallery_8505_416_25182.jpg

A split second later, the flexible bag material has responded to the pressure disequilibrium by bending under the atmospheric pressure. As a result, the bag is much smaller now, and close to the exterior of the meat. The external atmospheric pressure will continue to crush the bag material towards the meat until such time as the inside of the bag and the outside of the bag are at pressure equilibrium (illustrated by showing that the number of air molecules per square inch are the same inside and outside the bag). The meat inside the bag is now at regular atmospheric pressure.

gallery_8505_416_31821.jpg

What if you remove 100% of the air from the bag? Well, much the same thing happens. You go from this situation when the chamber is opened:

gallery_8505_416_10186.jpg

To this situation a split second later:

gallery_8505_416_15149.jpg

The only difference is that there is a small amount of air remaining in the bag in the first example, and no air remaining in the bag in the second example. In both cases, the steak is under regular atmospheric pressure once the bag collapses.

The only way to have the steak under low pressure after the chamber is opened is to have the steak inside a rigid container. If the walls of the chamber cannot contract, then there can be no pressure equilibrium and the steak will remain under lower pressure. You end up with this situation:

gallery_8505_416_10186.jpg

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I currently smoke a brisket for a beef duo on the menu, but I haven't thought about the sous vide idea for it.  In other words, I just smoke until it's done.  Anyway, what would the optimal cooking temperature be for the sv of a brisket?  It is not a collagen rich cut, as far as I'm concerned, so would you do like e_monster recommends and go for a lower temperature, but not as long of a time, like maybe for 18 to 20 hours?  In other words, why such extended water time?  What is the benefit of 48 hours, or another way of putting it, what is the gastronomic difference between the brisket at 24 hours and 48 hours?  Is is just to be on the safe side?  By the way, I'm thinking of a brisket flat or some call it brisket nose off.

As several people have slipped in ahead of this, brisket is collagen rich; that's why it makes such a magical transformation when smoking or braising.

I was looking for several basic things in the experiment:

- Is a 2-hour smoke then SV enough to impart smoke flavor? YES

- Is the SV result better than the smoked result under set conditions? YES

- Do the conditions chosen give great results? NO. (But certainly not terrible)

I chose WAG conditions with the reasoning that because brisket is tough and benefits from long and low, but the lower temperatures for a better cut of meat did not feel right, I'd need to go higher. Thus, 146F. Why 48 hrs? It seemed long enough. But, given the result (tougher and drier than I'd like, more gray than pink) and comments, I suspect that it was high enough to contract the muscle (squeezing out too much water), negating the benefits of collagen breakdown. So, as mentioned above by several posters, I'll try it again at a lower temperature, probably for 2 or 3 different times.

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sygyzy,

The results you got are not unusual, and in fact could be quite desirable, although the broken seal doesn't make for the best SV experience ( we all have seen it happened , though).

Does anyone know why this happens? I know Food Saver says you can put their bags in boiling water so the 130-140 F water shouldn't have mattered.

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I have used the FoodSaver hundreds of times and have never had a good seal break BUT it is possible to create a less than optimal seal if you aren't paying close attention and either get the area where the seal will be too wet OR have a tiny tiny little wrinkle that keeps the bag from being sealed well. I think if you inspect the seal after it is done, you won't have any problems.

When vac-packing moist foods, it is possible to have an improperly sealed bag without realizing it. It is also possible to have a little wrinkle that interferes with sealing. A few weeks ago, I was a little careless and vac-packed a porkloin with a wee bit of marinade. The seal seemed fine (i.e. the bag shrunk down and didn't expand when the FoodSaver was opened. I put the bag in the fridge and when I took it out half an hour later, the bag was no longer tight around the food. Upon close inspection, there was a small area where the bag had not really sealed well. It was pretty obvious when I looked at it.

sygyzy,

The results you got are not unusual, and in fact could be quite desirable, although the broken seal doesn't make for the best SV experience ( we all have seen it happened , though).

Does anyone know why this happens? I know Food Saver says you can put their bags in boiling water so the 130-140 F water shouldn't have mattered.

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- and boiling point is irrelevant to s-v cooking. (Because pressure - and so boiling point - isn't changed, as above.)

OK, I just want to get done with this issue.

Vacuum in SV is needed for the following reasons:

1. To remove oxygen, and as such to prevent change in color, tast, smell, texture and taste caused by oxygenation.

2. To preserve shape of a "substrate" inside a SV bag - pressure INSIDE the bag is approaching zero, pressure ON the bag is full atmospheric pressure.

3. To prevent evaporation/loss, and as such product shrinkage - important because boiling point of water is lower under vacuum/near vacuum conditions.

There are some other secondary considerations as well.

For anyone still in doubt I would recommend to check "Sous-Vide"by Roca and Bregues, or wait for "Under Pressure" to pop-up at Barnes&Nobles.


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

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Since it seems like you are getting your info from the books you own could you cite the page references?


My soup looked like an above ground pool in a bad neighborhood.

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More practical application:

I cooked Hanging Tenders at 64C, for 90 minutes.

I used an immersion circulator and Cryovac sealed tenders:

gallery_57905_5970_4642.jpg

Meat was very tender, and retained a slight "gamey" taste:

gallery_57905_5970_12529.jpg

Finished in clarified butter, with salt and spices - temp/time settings would be applicable for any medium-rare single muscle application, in my opinion.

This is what the final dish looked like:

gallery_57905_5970_911.jpg


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

***************************************

My flickr collection

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2. To preserve shape of a "substrate" inside a SV bag - pressure INSIDE the bag is approaching zero, pressure ON the bag is full atmospheric pressure.

Hi Mike,

I am fairly certain that your assertion about the pressure is mistaken.

As long as the bag is exposed to atmospheric pressure, the pressure is the same inside and outside the bag. If the bag is exposed to atmospheric pressure, the contents are at atmospheric pressure. It is that simple. If you were dealing with a rigid container, the inside and outside would be at different pressures. But that isn't the case.

If you have a cookbook that says otherwise, then the author is mistaken. Perhaps you are mis-reading the text.

--e


Edited by e_monster (log)

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As long as the bag is exposed to atmospheric pressure, the pressure is the same inside and outside the bag. If the bag is exposed to atmospheric pressure, the contents are at atmospheric pressure. It is that simple. If you were dealing with a rigid container, the inside and outside would be at different pressures. But that isn't the case.

May we entertain the idea that cellular structures (along with veins and capillaries) of proteins and vegetation, are semi rigid (elastic)?

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There are effects that are possible only with machines that can pull high inches of mercury. But they're not the effects that you're generally talking about. Having a super-strong vacuum machine is really not so important once you're actually cooking the food in the water bath. Rather, the interesting things that a strong machine are things like pressure "cooking" tender greens, compressing vegetables and fruits, sucking the air out of certain vegetables and fruits so that they "vacuum infuse" a liquid once the pressure is released, etc.

1. To remove oxygen, and as such to prevent change in color, tast, smell, texture and taste caused by oxygenation.

This can be important for long cooking times. However, the bar is significantly lower than "total vacuum." Semipro bag sealers such as these can pull 28 inches of mercury, which is more than enough if you're concerned about oxidation. Air is only around 20% oxygen by volume. I wouldn't recommend cooking short ribs for 48 hours inside of a ziplock bag. But even a cheap FoodSaver whould be able to reduce the air in the bag to less than 3 to 5 cubic centimeters (this is a worst-case scenario). That's simply not enough oxygen to make a huge difference.

2. To preserve shape of a "substrate" inside a SV bag - pressure INSIDE the bag is approaching zero, pressure ON the bag is full atmospheric pressure.

Mike, you still misunderstand. So long as the bag is able to shrink to the point at which the inside of the bag and the outside of the bag are at pressure equilibrium (which will happen 100% of the time under normal conditions), the pressure inside the bag is normal atmospheric pressure. In actuality, once it goes into the water bath, the contents of the bag are under slightly higher than normal atmospheric pressure due to the weight of the water above the bag.

As for preserving the shape of the food that is bring cooked, it is necessary to pull a reasonably strong vacuum before the bag is sealed, but nothing beyond the capabilities of a FoodSaver. Before I got my current semiprofessional bag sealer, I was able to do things like deboning and rolling up salmon steaks into a puck-shaped "salmon fillet mignon" -- and never had any difficulties with anything keeping its shape.

3. To prevent evaporation/loss, and as such product shrinkage - important because boiling point of water is lower under vacuum/near vacuum conditions.

This statement reflects several misunderstandings on your part.

First, as I explained at a level I think would be understandable to a seventh-graded, the contents of the bag are not under lower pressure once the bag collapses. This happens instantly when the chamber is opened, or simultaneously with the air being evacuated from the bag when it is an edge-sealer machine.

Second, as a result of the fact that the contents of the bag are not under less than 14.7 pounds per square inch of pressure ("normal" sea-level atmospheric pressure). But, let's say that it is under less than 14.7 PSI. How low do you suppose the pressure would have to be in order for the boiling point of water to be lowered to a temperature that would be significant to us? For the most part, we're cooking in the neighborhood of 60C. Water boils at 60.8C when it is at 3 PSI. Simple physics suggests that there is no way a steak inside of a collapsed bag and submerged under several inches of water is anywhere near as low as 3 PSI.

Third, evaporation is not a significant issue when one is cooking in a closed bag significantly under the boiling point of water. Other factors, such as water loss due to contraction of muscle fibers, etc. are the primary reasons for water loss in sous vide cooking.


Edited by slkinsey (log)

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As long as the bag is exposed to atmospheric pressure, the pressure is the same inside and outside the bag. If the bag is exposed to atmospheric pressure, the contents are at atmospheric pressure. It is that simple. If you were dealing with a rigid container, the inside and outside would be at different pressures. But that isn't the case.

May we entertain the idea that cellular structures (along with veins and capillaries) of proteins and vegetation, are semi rigid (elastic)?

That would only be germane to this fork of the discussion if one were somehow able to lower the pressure inside the cells, veins and capillaries only, such that the walls of the cells, veins and capillaries represented the boundary between higher pressure on the outside and lower pressure on the inside without collapsing.

As others have pointed out, the only way to have the food under less than 14.7 PSI is to put the food inside a rigid container and lower the pressure inside the container. In this case, following your idea that the cellular structures (along with veins and capillaries) of proteins and vegetation are semi rigid and thus somehow able to maintain pressure disequilibrium, the pressure inside these cells and inside these veins and capillaries would be higher than the pressure inside the chamber.


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make sure you know what you're talking about before you start telling people to seek out a seventh-grate physics text book. I've got access to several of the most important physicists and physical chemists of the latter half of the 20th century.  If you like, I could put the question to them and post their answers here. . .

slkinsey, thank you for your reply and input, among many other things it cools things down a bit.

Later today I would post references to support the statements I made above, and hopefully put this issue to rest. The physics and mechanics of SV process are important, although personally I am more interested in practical applications, such as temp/time, taste/texture experiences, etc. After all, this is a epicurean blog, although I am sure physicists have at least one of their own. :-)


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

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Mike, we're happy to have you share your experiences, and especially for you to share whatever you may have gleaned from books. But when you're making statements that are based on, e.g., Juan Roca's book -- especially statements which a reasonably informed person might hold to be incorrect from a scientific standpoint -- perhaps it would help to give context to your assertions if you would post the passages on which your assertions are based. This way other participants here can have some basis either to understand or critique your basis for making those assertions.

The deal about pressure inside the bag once the bag has been sealed and collapsed, I believe must be based on a simple misunderstanding on your part. Perhaps this based on something you read in one of these books -- we have no way of knowing if you don't post the basis of your assertions and simply continue to assert that you are correct and everyone else is wrong.

My own academic background is not as important in this case as the academic background of the parents who raised me. Both are chemists and my father is a noted physical chemist (member of the National Academy, festscrift edition of the Journal of Physical Chemistry, etc.) So not only did I literally grow up hearing about many of these basic principles (and really, the stuff we're discussing here is quite elementary) but I have a good basis for educating myself as to the topics that interest me and, perhaps most importantly, can count any number of famous scientists among family friends I could potentially ask to explain these things. My experience, however, is that things like this are at a basic-enough level that a simple query to a parent for support of my understanding or further explanation is sufficient.


Edited by slkinsey (log)

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Since it seems like you are getting your info from the books you own could you cite the page references?

Absolutely. The following references are from "Sous-vide Cuisine", Joan Roca/Salvador Brugués, Montagud Editores S.A.

Original title: La Cocina al Vacio

First published in 2003 by Montagud Editores, S.A.

©Third English edition: Montagud Editores, S.A. 2007

©Joan Roca and Salvador Brugués

©Francesc Guillamet

©Michael Debbane

©Montagud Editores, S.A.

Copyright Registration: B-26942-2007

ISBN: 978-84-7212-112-6

Chapter 3. Sous-vide Cooking , p.51

“We can broadly define cooking sous-vide as heating the food previously sealed in an airtight and heat-resistant container whose atmosphere has been modified ( a vacuum has been produced,, with or without elements such as gases, liquids, etc.).”

Chapter 3. Sous-vide Cooking , p.76

“ In the vacuum, the atmospheric pressure acting on the packaged product causes the water to vaporize before it would in the conventional cooking, in which pressure does not have as great of an impact on the final result (this means that the food will experience the effects of water vaporization at lower temperatures, along with all consequent modifications). This is therefore a very important fact that distinguishes sous-vide cooking from traditional methods.”

“ Pressure is one of the fundamental principles on which sous-vide is based, since it what allows a vacuum-sealed product to cook at low temperatures. Nonetheless, it remains a subject seldom studied by cooks-even though they have an inkling of its vast possibilities, the still don’t use it as a fundamental principle when cooking or intentionally seeking positive alteration of foods.”

Chapter 3, Sous-vide Cooking/ Technical Fundamentals p.84

“Our aim is to discover the why and how of the sous-vide cooking system through the analysis of the following parameters:

- Oxygen-free atmosphere

- Airtight containers and effect on pressure

- The time/temperature relationship

THE OXYGEN-FREE ATMOSPHERE

In this section we study a factor that plays a crucial role in cooking foods and, as a result, in their final quality… One of these potential alterations, … ,is oxidation, a reaction that occurs when oxygen bonds with other elements in food. Let us remember that these alterations manifest themselves in changes in color, odor, flavor, in its organic properties, etc.

When we cook sous-vide, and thus without oxygen, we prevent these reactions.4

… Another area affect by a lack of oxygen is enzymatic reactions, because the enzymes’ behavior is inhibited."

Bottom of the page, left corner, light grey font:

“4. The majority of food reactions are hydrolysis or oxidation; therefore, these reactions must be slowed to preserve or improve preparations. One way of doing this is to eliminate one of the reactants ( in this case oxygen).”

Chapter 3, Sous-vide Cooking/ Technical Fundamentals p.85

“AIRTIGHT CONTAINERS AND THE EFFECTS OF PRESSURE

COOKING SOUS-VIDE WITH THE EFFECT OF PRESSURE

Pressure has a fundamental effect on foods and provides a series of advantages in preparation that would be difficult to attain by traditional methods. The bag in this case acts as a second skin or direct protection for the ingredient ( especially in the case of shrink bags) and subjects it to constant pressure.

The main functions of the airtight containers are:

1. To support or hold the ingredient’s natural structure so that it does not break apart (e.g., foie gras).

2. To exert equal pressure over the entire surface of the ingredient. This evens out the cooking time for many ingredients (e.g., asparagus).

3. To prevent changes in weight from the ingredient drying out during cooking, thanks to the airtight container and the use of low temperatures.

4. To stop aromas from volatilizing, thereby enriching the preparation. The container helps to lock in the ingredient’s natural flavors; in fact, it serves the purpose of closing pores. This also occurs in cooking by concentration, but here there is no need to apply high temperatures that could denature or alter the ingredient’s initial flavor.”

“Sealing in shrink bags: guaranteed pressure” (highlighted in grey, upper left corner ,p.85)

“ All vacuum-packaged foods are subject to exterior pressure due to the absence of air in the bag. Sous-vide preparation sometimes requires the product to remain under pressure during the cooking process. Certain ingredients subjected to high temperatures during sous-vide cooking do release water vapor due to the heating of their own water.6 The bag then undergoes some interior pressure, causing it to lose some of the effect we are looking for.”

Middle of the page, footnote, highlighted in grey:

”6. In sous-vide conditions, water vapor forms at much lower temperatures than in normal atmospheric pressure conditions.”

I don’t know if a definition of vacuum is even needed at this point, but according to The American Heritage® Dictionary of the English Language (Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2003. Published by Houghton Mifflin Company. All rights reserved.):

vac•u•um (v k y - m, -y m, -y m)

n. pl. vac•u•ums or vac•u•a (-y - )

1.

a. Absence of matter.

b. A space empty of matter.

c. A space relatively empty of matter.

d. A space in which the pressure is significantly lower than atmospheric pressure.

I hope this answers most of the questions we have discussed this week.


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

***************************************

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OK, I apologize for asking this question, but I don't think I have the inclination to read all 60+ pages of this topic for an answer...

Has someone compiled a table/chart of time/temps. I'm not really looking for a table that charts the bath temp. and then states how long the heat will take to penetrate the various thickness of the proteins...I'm looking for something along the lines of a compiled table of recommended time/temps for various proteins and veg. For example, chicken breast @ 147F for 2 hrs, salmon at 135F for 1 hour, etc, eggs at 140 for 3 hours. Maybe some info on times to effectively kill bacteria (like, chicken is OK at 148F, but you have to cook it for 4 hours to kill the germs).

I understand that a lot of the results are subjective, and of course some people want steak cooked at higher temps, etc. I am about to pursue in earnest setting up a home sous vide setup and would like some starting points.

I'm not asking anyone to compile a list for me, but if one exists out there or in the thread that would be great.

Thanks guys.

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So I made Sous Vide (the first time) chicken last Saturday to serve my guests in one of the dinner courses. 1 piece of breast and 1 piece of leg in 61C bath for about 3 hours (basically started cooking at 4 and serve straight for the course at around 7).

The chicken is "perfect". Good enough that I forgot I made a sauce for it.. :)

But, over the discussion, we figured what's wrong with Sous Vide cooking.. (My guests and us have both ate at a number of restaurants that use Sous Vide.. including the FL)

Our conclusion is that the food cooked in Sous Vide lacks "passion". It doesn't vary depends on the weather of day, the difference in the heat of the stove and the skill/execution of the chefs.

At the end of the day, it's like food mass produced from a factory..

- M

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Hi Mike. Thanks for posting the quotes from Roca. I can see how some of that stuff may be confusing.

Some quick thoughts below...

As to the stuff on Page 76: I believe Roca must be talking about cooking food in a rigid container rather than a flexible container. As I and others have mentioned, it is possible to go under 14.7 psi in a rigid container -- it's just not possible in a container as flexible as a bag, because the container deforms until there is pressure equilibrium.

As to the stuff on Page 84: Roca is correct that removing most of the oxygen can have an important effect. However, we should understand that even if we remove all the air from the bag, we have not removed all the oxygen from the cooking environment -- there is still oxygen in the meat itself. So the question is not whether we have removed all of the oxygen, because this is impossible. The question is how much oxygen we have removed. When we are considering vacuum machines of different strengths, there is a question as to whether the difference in the oxygen removed is large enough to make a significant difference on a chemical basis. My strong suspicion is that, so long as the vacuum machine is reasonably strong (say >25" Hg), there is not going to be a significant difference. More on this later.

As to the stuff on Page 85: No one disagrees that sous vide bags support the ingredient's structure, help to exert equal pressure over the entire surface of the ingredient, help to prevent drying due to moisture loss (also significantly due to cooking at lower temperatures) and help to prevent aroma/flavor loss due to volatization.

The question is how strong the vacuum machine has to be in order to accomplish these things. Certainly, a stronger machine may create a situation in which the bag material presses against the food more evenly, but this doesn't necessarily argue for a zillion dollar machine. As I have pointed out, I've been able to compress and support salmon steaks rolled up into a "salmon fillet mignon" very well with a run of the mill FoodSaver. For sure there are likely some effects that would be done better with a stronger machine (e.g., an extremely delicate food that does not want to cohere).

Please take note: As you can see in the passages you quoted, when Roca talks about pressure, he is talking about the bag pressing on the food inside. This directly contradicts your earlier assertions that the contents of the bag are under less-than-normal pressure. Indeed, physics tells us that the bag is pressing inwards on the food with exactly the same force that is being applied externally on the bag. In this case, it is 14.7 psi when the bag is not in the water bath (normal atmospheric pressure), and slightly more than 14.7 psi when the bag is in the water bath (where pressure is higher due to the weight of the water).

As to the "highlighted in gray" material on Page 85: This is true if the food is inside a rigid container. If it is in a bag, it is not true.

I have a proposal: Let's come up with a series of questions about pressure and oxidation reactions as they apply to sous vide cooking. We'll agree on a list of questions, and I will send them to this guy, who I hope we can agree has a level of expertise that should provide for a definitive resolution to these questions. He is familiar with sous vide cooking, having had several examples prepared by me.

Here are a few questions I propose:

1. A piece of steak is sealed inside an impermeable flexible plastic bag in a zero-atmosphere environment. The bag is exposed to normal atmospheric pressure, and the bag deforms to tightly cover the meat. Is the meat now under (1) normal atmospheric pressure; or (2) less than normal atmospheric pressure?

2. Let's suppose that the bag is sealed inside an environment that is somewhat less than zero-atmosphere. Let's say that the machine is capable of 25" Hg, so there is a tiny bit of air left inside the bag. Is this difference likely to have any significant effect as to oxidation reactions when the food is cooked at 60C?


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As to the stuff on Page 76:  I believe Roca must be talking about cooking food in a rigid container rather than a flexible container.  As I and others have mentioned, it is possible to go under 14.7 psi in a rigid container -- it's just not possible in a container as flexible as a bag, because the container deforms until there is pressure equilibrium.

Although R&B mention rigid containers in the book (specifically - jars), virtually all of their SV cooking ( "direct" and "indirect", according to their classification) is done in various types of flexible bags, and as such, those containers are the primary subject of their research and conclusions.

As to the stuff on Page 85:  No one disagrees that sous vide bags support the

ingredient's structure, help to exert equal pressure over the entire surface of the ingredient, help to prevent drying due to moisture loss (also significantly due to cooking at lower temperatures) and help to prevent aroma/flavor loss due to volatization.

There was some heavy criticism of the points above, which is why I had to quote this particular paragraph.

...As you can see in the passages you quoted, when Roca talks about pressure, he is talking about the bag pressing on the food inside.  This directly contradicts your earlier assertions that the contents of the bag are under less-than-normal pressure. 

The contents of the bag are under vacuum, which is by definition less than atmospheric pressure.

As to the "highlighted in gray" material on Page 85: This is true if the food is inside a rigid container.  If it is in a bag, it is not true.

R&B are quite clear on this one - the title of the highlighted text box is “Sealing in shrink bags: guaranteed pressure”.

The theory of SV is interesting and important, indeed. Personally, I would like to concentrate on SV recipes, techniques and experiences, at this time.


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

***************************************

My flickr collection

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The theory of SV is interesting and important, indeed. Personally, I would like to concentrate on SV recipes, techniques and experiences, at this time.

Does this mean you are giving up and admitting the material in your books is incorrect and in some cases confusing to the point that it may as well be incorrect? I just want to know before I spend the time pointing out the flaws. If you are giving up I will as well.


My soup looked like an above ground pool in a bad neighborhood.

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As to the stuff on Page 76:  I believe Roca must be talking about cooking food in a rigid container rather than a flexible container.  As I and others have mentioned, it is possible to go under 14.7 psi in a rigid container -- it's just not possible in a container as flexible as a bag, because the container deforms until there is pressure equilibrium.

I have to admit that I was baffled by some of the statements in the Roca/ Brugués book, but I mostly glossed over the confusing passages in favor of the seemingly definitive information about sous vide cookery contained in the book. I still value the practical application information in the book, and I think the discussion of sanitation issues is accurate, but MikeTMD's citation of the stuff about vacuum, etc., gave me pause. I had to go back to page 76 to see for myself.

There's no question that Roca et al. state that water behaves differently under reduced pressure. However, it's implied that this applies to food sealed in a bag:

In the vacuum, the atmospheric pressure acting on the packaged product causes water to vaporize before it would in conventional cooking, in which pressure does not have as great an impact on the final result (this means that the food will experience the effects of water vaporization at lower temperatures, along with all of its consequent  modifications). This is therefore a very important fact that distinguishes sous-vide cooking from traditional methods.
(my emphasis added)

This discussion is accompanied by FIGURE 1 / Effect of temperature-pressure relationship on water states. The figure shows the lowered boiling point of water vs. reduced pressure. As Sam has pointed out, this would only apply when the food is sealed in a rigid container. Roca et al. seem to be talking about sous vide cooking as we know it (food sealed in a bag). So this part of the "definitive" book on sous-vide would appear to be incorrect. Perhaps the very term "sous vide" is unfortunate, since it leeds people to think that the food is actually "under vacuum" when cooked, rather than just vacuum-sealed.

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The theory of SV is interesting and important, indeed. Personally, I would like to concentrate on SV recipes, techniques and experiences, at this time.

Does this mean you are giving up and admitting the material in your books is incorrect and in some cases confusing to the point that it may as well be incorrect? I just want to know before I spend the time pointing out the flaws. If you are giving up I will as well.

I never meant for this discussion to become competitive - my primary goal is to learn what can I do to enjoy better food ( prepared by others, or otherwise). So it is not about "giving up", or "staying the course".

There is a difference of opinions - no doubt, but every point of view should be heard. As such, please share yours.


"It's not from my kitchen, it's from my heart"

Michael T.

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... part of the "definitive" book on sous-vide would appear to be incorrect. Perhaps the very term "sous vide" is unfortunate, since it leeds people to think that the food is actually "under vacuum" when cooked, rather than just vacuum-sealed.

Do you mean vacuum sealed by FoodSaver type equipment? I am not very familiar with FS - does it just vacuum-seal the cooking bags, or does it create some kind of vacuum? ( I always used a vacuum chamber machine packaged food - sometimes at the cost of having better vacuum over proper and essential seasonigs and spices)


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

***************************************

My flickr collection

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I always used a vacuum chamber machine packaged food - sometimes at the cost of having better vacuum over proper and essential seasonigs and spices

Do you mean to say you don't have a vacuum sealer and that you are cooking cryovac'd foods in the plastic you purchased them in?


My soup looked like an above ground pool in a bad neighborhood.

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I always used a vacuum chamber machine packaged food - sometimes at the cost of having better vacuum over proper and essential seasonigs and spices

Do you mean to say you don't have a vacuum sealer and that you are cooking cryovac'd foods in the plastic you purchased them in?

I usually ask a mom-pop butcher down the street to use their vacuum-chamber machine to seal my bags after I fill them ( for a $1 per bag - truly a bargain). That said, I buy Cryovac'd portioned flat iron steaks and hanging tenders from a wholeseller, and - guilty as charged, SV them in the industrial strength vacuum bags they come in, but season them agressively prior to browning.


Edited by MikeTMD (log)

"It's not from my kitchen, it's from my heart"

Michael T.

***************************************

My flickr collection

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