What's your impression of sous vide?

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[quote name="dcarch" url="/t/8

Sous vide is a fancy French word for a shockingly simple cooking method, that is, cooking with an extremely good thermostat. No more and no less.

dcarch

Actually, any French speaker will tell you,
Sous=under
Vide=vacuum

Then again all web resources will tell you that sous vide entails cooking in some form of an airtight container, and about half will tell you that the container is under vacuum, hence the french term "sous vide".[/quote]
You are correct in the French language. You are also correct that originally (historically) vacuum was considered part of the sous vide idea.

But scientifically, it is not possible to create pressure in a flexible plastic bag. Try it. Use the most powerful vacuum machine to draw a vacuum in a plastic bag. At the end if you measure the pressure, it will be the same as atmospheric pressure. You can only create vacuum (pressure) in a rigid container.

Again, neither vacuum nor pressure is needed to keep precise temperature setting. 

dcarch
 
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I'm a French speaker. Sous-vide means under vacuum, correct, because it was originally thought that by using a vacuum packing machine you were creating a vacuum in the bag, but it has since been shown that there's no such thing. You do use an air-sucking machine to remove the air from the bag, but when doing so, the bag collapses around the items and poaching liquid, leaving no space at all for sous-vide (vacuum). In a vacuum packed bag, there is no vacuum. 

A vacuum is a space devoid of matter. You would need a pretty sturdy container to contain a vacuum - not a plastic bag, that collapses when you remove the air from it. 

[EDIT: Just realized I'm pretty much saying the same thing dcarch already said.]
 
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foodpump, you can call precise temp cooking poaching all you want.  But you are wrong.  I can call Crock pots bbq, too.  Or EZ bake ovens the same as Rational ovens.



O.K. Why am I wrong?

Poaching is done at temps from 65-85 c in some kind of liquid. Fair enough? Precise temp or not, that is the cooking method. The technique for s.v. Is to put item in a bag, suck the air out, seal the bag, and immerse it in water of a set temp. Below the boiling point. Sound familiar? Technique and cooking method are not the same.

Look, using you suggestions of ovens, I've baked bread in just about every type of oven imaginable. The cooking method is baking--dry heat with no moisture or fat. I can use a convection, a deck, a Rational, a wood fired stone beehive oven or an Ez-bake oven (my sister got one of those for christmas, didn't last long after I took it apart). But the cooking method is the same
 
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....since been shown that there's no such thing. You do use an air-sucking machine to remove the air from the bag, but when doing so, the bag collapses around the items and poaching liquid, leaving no space at all for sous-vide (vacuum). In a vacuum packed bag, there is no vacuum. 

A vacuum is a space devoid of matter. You would need a pretty sturdy container to contain a vacuum - not a plastic bag, that collapses when you remove the air from it. 

[EDIT: Just realized I'm pretty much saying the same thing dcarch already said.]
FF, you are speaking along the lines of physics and what would be considered a "perfect vacuum" - our handy dandy food savers that suck air out of the bag are in fact creating a vacuum, which simply means it is changing the air pressure inside the bag. Commercial vacuum chamber sealers create an even better vacuum but in either case the product in the bag is under the effect of an atmospheric pressure change due to the vacuum - this is why melon can be compressed this way and is still considered sous vide. So no offense, but I think the literal translation is accurate.
 
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Originally Posted by dcarch  

But scientifically, it is not possible to create pressure in a flexible plastic bag. Try it. Use the most powerful vacuum machine to draw a vacuum in a plastic bag. At the end if you measure the pressure, it will be the same as atmospheric pressure.
I don't agree at all. If the seal of a vacuum sealed bag is compromised air will come rushing into the bag until it reaches equilibrium with the surrounding atmospheric pressure, it does that because of the vacuum present.
 
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FF, you are speaking along the lines of physics and what would be considered a "perfect vacuum"
No, I am not talking about a perfect vacuum, I am talking about a vacuum, perfect or not. You cannot create a vacuum with a flexible container, that's just basic physics! If the pressure outside is bigger than the pressure inside, then the bag collapses, leaving no space inside - therefore no vacuum. If the container was rigid enough to withstand the pressure difference between outside and inside the container then you could create a vacuum. 
 
our handy dandy food savers that suck air out of the bag are in fact creating a vacuum, which simply means it is changing the air pressure inside the bag.
No they are not (creating a vacuum). A vacuum is a SPACE devoid of matter (http://www.merriam-webster.com/dictionary/vacuum). Food savers are removing the air and collapsing the bag, leaving no space devoid of matter behind. As dcarch pointed out, the pressure inside the bag after removing the air is exactly the same as it was before removing the air. 

I'm having difficulty understanding what you believe is going on in a bag after you remove the air out of it. Do you think your vacuum sealer removes the air but leaves an empty space instead, therefore leaving the same volume inside the bag? A simple test will show you that's not the case: suck the air out of a zip lock for example with your mouth, and the bag will collapse, to the point that it will be empty. No space left = no vacuum. Or were you under the impression that the food saver was changing the pressure of the liquid inside the bag? That's... just not happening. 

I have a few questions for you: 

1) Do you think there's air left after you vacuum pack a bag?

2) Do you think there's empty space left after you vacuum pack a bag?

3) Do you think the pressure of the liquid inside the bag has changed after you vacuum pack the bag?

(the answer to all 3 questions should be 'no')
 
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I don't agree at all. If the seal of a vacuum sealed bag is compromised air will come rushing into the bag until it reaches equilibrium with the surrounding atmospheric pressure, it does that because of the vacuum present.
That is true. Air will rush in if you cut a hole in the bag. The reason for that is because the bag material is not completely flexible. If you take a tennis ball, cut a hole and squeeze the air out by hand. The moment you let go of your hand the ball will suck the air back in. It does not mean there was vacuum inside the ball before.

In your example of compressing melon, it is possible because the melon is porous in structure. You can in fact create good vacuum and differential pressure if you bag a whole chicken and pull air out with a vacuum. The reason is because the rib cage of the chicken is empty and  rigid. 

The opposite is true also. You can never pressurize a balloon which has extremely flexible rubber. However, you can pressurize a soda bottle because the bottle does not stretch.

dcarch
 
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Kind of skimmed through these replies, but here is Wiki

https://en.wikipedia.org/wiki/Vacuum
 

Vacuum  is space  that is devoid of matter

The word stems from the Latin adjective vacuus  for "vacant" or "void".

An approximation to such vacuum is a region with a gaseous pressure  much less than atmospheric pressure.[sup][1][/sup]

Physicists often discuss ideal test results that would occur in a perfect  vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum  to refer to an actual imperfect vacuum as one might have in a laboratory  or in space.

In engineering and applied physics on the other hand vacuum refers to any space in which the pressure is lower than atmospheric pressure.[sup][2][/sup]  The Latin term in vacuo  is used to describe an object as being in what would otherwise be a vacuum.

 

The quality  of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure  means higher-quality vacuum. For example, a typical vacuum cleaner  produces enough suction  to reduce air pressure by around 20%.[sup][3][/sup]Much higher-quality vacuums are possible. Ultra-high vacuum  chambers, common in chemistry, physics, and engineering, operate below one trillionth (10[sup]−12[/sup]) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm[sup]3[/sup].[sup][4][/sup]  Outer space  is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average.[sup][5][/sup]  According to modern understanding, even if all matter could be removed from a volume, it would still not be "empty" due to vacuum fluctuationsdark energy, transiting gamma- and cosmic rays, neutrinos, along with other phenomena in quantum physics. In modern particle physics, the vacuum state  is considered the ground state  of matter.



Pressure ranges of each quality of vacuum in different units
Vacuum qualityTorrPaAtmosphere
Atmospheric pressure7601.013×10[sup]+5[/sup]1
Low vacuum760 to 251×10[sup]+5[/sup]  to 3×10[sup]+3[/sup]1 to 0.03
Medium vacuum25 to 1×10[sup]−3[/sup]3×10[sup]+3[/sup]  to 1×10[sup]−1[/sup]  
High vacuum1×10[sup]−3[/sup]  to 1×10[sup]−9[/sup]1×10[sup]−1[/sup]  to 1×10[sup]−7[/sup]  
Ultra high vacuum1×10[sup]−9[/sup]  to 1×10[sup]−12[/sup]1×10[sup]−7[/sup]  to 1×10[sup]−10[/sup]  
Extremely high vacuum<1×10[sup]−12[/sup]<1×10[sup]−10[/sup]  
Outer space1×10[sup]−6[/sup]  to <3×10[sup]−17[/sup]1×10[sup]−4[/sup]  to < 3×10[sup]−15[/sup]  
Perfect vacuum000
 
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So what does this mean to us?

Basically, unless you're in a black hole, you wont experience what is known as a "perfect vacuum," and even then we aren't 100% sure that's the case.

We are looking at "partial vacuum."

The problem isn't creating a void, the thing we are looking to remove is "the air."  Air is evil, which is why we use vacuum sealers to stop oxidation in our foods.

The question is, does food oxidize at a faster rate under heat?  By removing air does this stop the oxidation?  Is this also one reason why we don't have some sort of "searing" on the meat, regardless of the temp?

I did try to look up what kind of pressure these commercial vacuum-sealers like "Foodsaver" put out, but couldn't find anything except http://www.pump-n-seal.com/comparison.htm 

which goes by hg in inches which has to do with mercury displacement.  From wiki it has to do with mmhg, so I'm not sure where inches came from....

If anyone knows conversions that would be great, but too tired to figure it out now.
 
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You know what.. I'm not going to get into a debate on the physics of a vacuum and whether or not what is done using a vacuum chamber or food saver meets the popular opinion here.

How about the terminology referring to vacuum packaging. Which wikipedia defines as:

"Vacuum packing is a method of packaging that removes air from the package prior to sealing".

Suffice it to say that definition is all that is needed in the discussion of sous vide cooking.
 
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We are looking at "partial vacuum."
No - and other than making the statement, I'm not sure how you reached that conclusion. There's no partial vacuum in sous vide. There's no vacuum at all. There's no difference in pressure between the outside of the bag and the inside of the bag. 
 
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No - and other than making the statement, I'm not sure how you reached that conclusion. There's no partial vacuum in sous vide. There's no vacuum at all. There's no difference in pressure between the outside of the bag and the inside of the bag. 
That is what the sealers do, apply a vacuum to the product, a partial one, as outlined by my comment above.  Where the range falls it TBD.

Unless there is a leak in the bag, the contents will stay under pressure, with no air, or minimal air, in the bag.

What do you think it does?

As for

 
 here's no difference in pressure between the outside of the bag and the inside of the bag. 
http://www.mindtrekkers.mtu.edu/docs/TrashBagandVacuum.pdf


 
 4. Turn on vacuum. It should quickly suck all the air of the bag, making it so your volunteer is “vacuum sealed” in by lowering the air pressure inside the bag, the air pressure outside is greater and presses on them.


5. Have them try to move.

6. Turn vacuum off and explain the science.

7. At sea level, the Earth’s atmosphere presses 14.7 pounds per square inch. Air has weight. The pressure inside the plastic bag is lowered by the vacuum to ~12.5 PSI and the atmosphere on the outside of the bag is 14.7 PSI, with a difference of 2.2 PSI, there is more pressure outside.



Conclusion: The weight of the atmosphere is on our shoulders, we just don’t notice it. When the pressure is lower inside the trash bag than the pressure outside the trash bag you notice this change and can feel the atmospheric pressure. 
For some reason i thought this was an MIT study, but the facts are still the same.

But again, a lot of people in here are believing what they want, and that's okay, but we aren't actually presenting "facts," and this will not get us anywhere.

In reality, There is no point in me posting further, I just wanted to hear people's opinions on SV, not hear a bunch of arguments about what is, or is not a vacuum, and nothing to do with the actual topic of SV.

Carry on peeps!

 
 
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The sealers apply a vacuum to the product so that the air inside the bag is sucked in by the sealer. The result does NOT leave a vacuum inside the bag!! A vacuum would be left inside the bag if the bag didn't shrink when you vacuum sealed it, and that's only possible with a rigid container.

When you vacuum clean your house, you apply a vacuum on the floor so that the dust is sucked in by the vacuum cleaner. The result does NOT leave a vacuum inside your house!!

Look let's keep this simple: 

1) A vacuum is a space devoid of any matter. 

2) Show me a photograph of a vacuum packed item prepped for sous vide, and point to the space devoid of matter - it should be clearly visible. 

3) Try using a food sealer on a bag full of air. Once you're done, show me the empty space inside the bag. 
 
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The sealers apply a vacuum to the product so that the air inside the bag is removed. The result does NOT leave a vacuum inside the bag!!

When you vacuum clean your house, you apply a vacuum on the floor so that the dust is removed. The result does NOT leave a vacuum inside your house!!

Look let's keep this simple: 

1) A vacuum is a space devoid of any matter. 

2) Show me a photograph of a vacuum packed item prepped for sous vide, and point to the space devoid of matter - it should be clearly visible. 
If you actually read my first post from wiki, all of these answers would make sense.

You also didn't read the post that shows that these vacuum sealers apply pressure, nor the post in my second post..

Your vacuum analogy doesn't make sense, because you are applying a small vacuum to your OPEN house, it's like saying you're vacuum sealing a food saver bag with a vacuum cleaner, you're not going to do anything to it, because it's nto sealed..  If you applied your entire house under vacuum, with no way for air to get in the house (a giant bag), it would be under pressure, just like the experiment they did in my second post, which shows humans under pressure in the bag, and just like the meat we are sealing in the bag, but more so, because the food in the bag is sealed tight.


From my first post 
 In engineering and applied physics on the other hand vacuum refers to any space in which the pressure is lower than atmospheric pressure.[sup][2][/sup]  The Latin term in vacuo  is used to describe an object as being in what would otherwise be a vacuum
So in Physics and Engineering, A vacuum is "any space in which the pressure is lower than atmospheric pressure."


Again, I'm not here to argue this, nor do I know why I even looked at your reply, especially if you aren't going to even spend the time to read my replies, and understand what's going on.  Instead you are just commenting the same thing that was said in a previous post.  Go do your own research, and form your own opinion.  I might be wrong, but you're not convincing me, nor have you provided ANY credible material, like I have.

Have a good one man, enjoy.
 
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All this to say that the French translation got it wrong? But using a translator "vacuum packed" is still translated as emballé sous vide .. sous vide is still the appropriate term. Even Thomas Keller's book is titled "Under Pressure - cooking sous vide" I hope we are done with this lol
 
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If you actually read my first post from wiki, all of these answers would make sense, which is something I should have said in my second post, because it was clear then, you didn't read it.

You also didn't read the post that shows that these vacuum sealers apply pressure, nor the post in my second post..

Your vacuum analogy doesn't make sense, because you are applying a small vacuum to your OPEN house, it's like saying you're vacuum sealing a food saver bag with a vacuum, you're not going to do anything to it, because it's nto sealed..  If you applied your entire house under vacuum, with no way for air to get in the house (a giant bag), it would be under pressure, just like the experiment they did in my second post, which shows humans under pressure in the bag, and just like the meat we are sealing in the bag, but more so, because the food in the bag is sealed tight.

Again this shows you didn't read my second post....

From my first post 

So in Physics and Engineering, A vacuum is "any space in which the pressure is lower than atmospheric pressure."


Again, I'm not here to argue this, nor do I know why I even looked at your reply, especially if you aren't going to even spend the time to read my replies, and understand what's going on.  Instead you are just commenting the same thing that was said in a previous post.  Go do your own research, and form your own opinion.  I might be wrong, but you're not convincing me, nor have you provided ANY credible material, like I have.

Have a good one man, enjoy.
Actually I did read your posts and the links they contained, they just don't disprove my point at all, contrary to what you seem to believe. 

But you didn't address my own post??? --> Can you show me a photograph of a vacuum sealed bag and point to the empty space in it? Can you use a food saver to apply a vacuum to a bag full of air and show me the empty space left inside the bag?
 
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All this to say that the French translation got it wrong? But using a translator "vacuum packed" is still translated as emballé sous vide .. sous vide is still the appropriate term. Even Thomas Keller's book is titled "Under Pressure - cooking sous vide" I hope we are done with this lol
The French who initially gave it the name "sous vide" got it wrong. Every other country correctly translating this wrong terminology got it just as wrong as the French originally got it wrong. 

Now let's all place a raw steak in a hot pan to "seal in the juices"!!! /img/vbsmilies/smilies/rolleyes.gif
 
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