blackp
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There is not that much difference in vaccum settings for most situations.
First off, you will never get a very strong vaccum no matter what you do, because the water in the food will evaporate. With any fresh meat or vegetable you can NEVER have a vacuum less than the vapor pressure of water, since you have water in the food. Note that even if the water in bag does not boil, it is nontheless evaporating.
A chamber style machine can draw enough of a vacuum to boil ice water, but there is little point in doing that. In general you want to draw enough of a vacuum to remove the residual air, but since you will never remove all of the water vapor, there is no point in attempting to pull a vacuum stronger than it takes to boil the water. You don't even need to go that far, but certainly there is no point in going farther.
Note that many vacuum sealers have a default program where they take the bag to 99% vacuum then hold it there for 5 to 10 seconds. The reason is NOT to draw the vacuum below 99%. In fact, depending on the temperature of the food it may not even reach 99%. The goal is to bring the bag to the point where the water in the food will boil. This fills the chamber with water vapor, which helps displace the residual air.
Note that a bit of boiling of water in the food like this is not going to hurt things.
Also, note that you are going to cook the food! Which means that ultimately the pressure in the bag is the vapor pressure of water at the cooking temperature. The original pressure in the bag is pretty much irrelevant.
As an example, if you cook at 60C/140F, then the vapor pressure of water is 19.9 kPa. Normal atmospheric pressure is 101.325 kPa. Vapor pressure of water at 5C/41F is 0.9 kPa.
So if you pack some chicken breasts (or other meat, seafood, vegetables) at 5C (typical refriderator temp), then no matter how hard the vacuum pump pulls, you will never get below a vacuum of 99.1% because that the level at which the ambient pressure equals the vapor pressure so the water boils. Realistically, you can draw a 99.0% vacuum but no more than that.
That will evacuate most of the air and thus oxygen, which is your real goal with sous vide vacuum packing anyway. The goal isn't the degree of vacuum, it is getting the oxygen out, and even then you ONLY care about the oxygen in some cases. If you are serving the food immediately and not storing it in the bag then you don't really care about the vacuum level. In fact, you can cook in an unsealed bag.
We seal and vacuum pack for storage, and a bit for convienence (keeps bags from floating...)
OK, so back to the example. If you pull a 99% vacuum at 5C, then seal it, the food bag is now at atmospheric pressure, because the bag is not strong enough to resist the pressure. In most normal cases with soft food, the bag does not contain a vacuum, and it is NOT "under pressure", despite the title of Thomas Keller's book on sous vide. Yes, it is true that atmospheric pressure pushes on the bag, but the atmosphere pushes on everything, so that doesn't count for anything meaningful.
The only real difference is that if you have a hollow space inside the food - a bubble or cavity - then in the atmosphere that cavity pushes back with the same atmospheric pressure. So, if you vacuum pack, you take that pressure out of the cavity, and it tends to collapse. Hollow foods - say a green pepper - will collapse in the vacuum bag. Stronger hollow foods - say a quail or cornish game hen - sealed in a vacuum bag are generally strong enough to resist the atmospheric pressure, so in that hollow space there will be a partial vacuum.
If you looked closely you would find that the bag has a small amount of gas in it - which is the residual air, and a small amount of water vapor. This is particularly true if the food has a hollow space, but it is even true for a soft food.
When you heat that bag up to 60C the residual air will expand a bit, and more water vapor will evaporate.
In fact, the amount of air and water vapor would be the same as if you vacuum packed the food at 60C temp, at which point you would get about an 80% vacuum.
Now, it is not true that you get a "80% vacuum in the bag" because for most foods there never is a vacuum in the bag once it is sealed. For a soft food, the amount of residual gas in the bag would be identical to one sealed at 60C, at which point the lowest possible vacuum in the chamber would be 80%. For a hard food with a hollow space in the middle, that hollow space would have a parial vacuum of 80%.
If instead you sealed at 90% vacuum at 5C, then heated the sealed bag up to 60C, the amount of residual gas would be a bit more - equivalent to sealing at 68% vacuum.
So, as you can see, there is not that much difference.
Some people, like Dave Arnold, say that they get big differences in results by their vacuum level. I totally respect Dave and his team, and we use many of their discoveries in MC, but I am not sure how to respond to this. In our tests we don't see a difference in the final quality. As the example shows the laws of physics pretty strongly suggest that there can't be much of a difference. My guess (but only that) is that there are some other issues at play here in how the food is handled, but I don't know for sure.
Fish are a particularly amusing example. It is often claimed that fish "can't take the extra pressure" of high vacuum packing.
First off, at a normal cooking temperature, there is very little difference in the amount of air in the bag. Fish don't typically have hollow spaces in them, so this is a moot point.
One reason that fish typically don't have hollow spaces is that fish can generally swim pretty deep. Almost any fish can swim 33 feet (10 meters) deep, at which point the fish is under TWICE atmospheric pressure. At 66 feet / 20meters it is 3 atmospheres and so forth.
Deep dwelling fish, like a monkfish live routinely in a 10-20 atmospheres of pressure.
So, fish, all of animals, are built to take a lot of hydrostatic pressure, and thus should not have a sous vide pressure effect.
Finally, note that "bag pinch" where you can see where the bag came together can affect any food, but that little bag seam is not generally a quality problem.
Thanks Nathan for your considered response (and subsequent replies on this sub-topic about surface boiling).
I am now happy that I understand why I got the results I did. I still cannot understand Dave Arnold's observation, and like you I have a lot of respect for the FCI guys - I have learnt a lot from them.
It could be interesting to try vacuuming something for a very long time, but given you would never do this in normal practice I don't think that it would be very useful.
Thanks again,
Peter.
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Anyone know of a reasonable device, that can sense both the highs and lows of the water bath and will alarm you if your bath range goes outside a : for example .5 ( F ) degree window.
So if I would sous vide ribs for 36-48 hrs. I would like an alarm if the thermal circulator goes whacky?
I see in a previous thread, that a second device is recommended.. in helping monitor the high end.
Thanks Paul
I use a Sous Vide Magic to control my SV cookery. It allows the setting of high and low temperature alarms, although I'd be reluctant to attempt to set those to 0.5°F. If I did it would go off while it was coming up to temp and would go off again when I put my food in to cook.
You should run some experiments with your SV device to see how accurate it is using a trusted thermometer.
Once you know how your device behaves you can then trust it to work for you.
If you are trying for the perfect poached egg at 64.5°C you need to be sure that the temp is not drifting (especially higher), but that doesn't take more than an hour. For most long term cooking stability inside 1 or 2 degrees should be OK.
I often cook beef ribs for 48 hours and usually do that at 57°C which is low enough for them to still be a bit pink when done. If they were cooked at 57.5°C or 56.5°C I'm sure I wouldn't notice much difference.
My point is that subtle temperature differences seem to have less impact for long term cooking and are more important for things cooked briefly like eggs or fish.
Cheers,
Peter.
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The vacuum level dilemma with chamber sealers for sous vide cooking
Edge sealers suck all air out of the bag before sealing, tightly fitting the bag to the food; so even with low vacuum levels, there is virtually no air left in the bag, except for some surface irregularities of the food to which the plastic may not have been snugly fitted. Maximum vacuum levels achieved by edge sealers (80-90%) will not damage food by cold boiling and/or compression (see Dave Arnold's "Boring but useful technical post: vacuum machines affect the texture of your meat" and Modernist Cuisine page 2•213 "Boiling not Crushing").
In contrast, chamber sealers suck the air out of the bag and its surrounding, then seal, and the bag will only be fitted tightly to the food after releasing the vacuum from the chamber. To fit the bag snugly to the food, vacuum levels of 99% to 99.9% are applied. These vacuum levels may damage delicate food like fish or poultry. Reducing the vacuum level in a chamber sealer to e.g. 80% may leave some air in the bag causing floating and poor heat transmission: if the initial air volume between food and bag was e.g. 200ml, after sealing in an 80% vacuum there will be 40ml of air (that’s a jigger!) left in the bag.
If there is no edge sealer at hand for sealing delicate food, a Ziploc bag may be preferable to the chamber sealer.
A way out with a chamber sealer might be using a sealed bag of water to weigh down the bag to be sealed and eventually a second sealed bag of water below the bag to be sealed, thus displacing as much air as possible out of the bag before sealing.
Pedro sent me this observation a few days ago and I checked his theory and can confirm it is correct. I had a chamber machine for some years before embarking on SV cookery, but had always used 99%+5sec. vacuum (or similar) for hard items and around 97% vacuum for softer products, based on my experience using the machine for freezing.
I had never even tried 80% vacuum for SV but prompted by Pedro I did and can confirm that items packed at even 90% vacuum will float in a water bath. With my machine settings of 95% or higher will remove enough air from the bag to allow it to sink without any help from weights or other devices. Note that my machine has a vacuum sensor to determine the level of vacuum rather than a timer which is used in some machines.
Dave Arnold from FCI published an article a while back (cited above in Pedro's post) which shows different results from bagging at different vacuum levels. In a recent dialogue Dave observed that even items vacuum packed to high levels and then re-packed into low pressure bags did not exhibit the same impact as those vacuumed to the same level and cooked in that bag.
Nathanm et. al. in Modernist Cuisine (2.213) suggests that the strong vacuum causes boiling which damages cells close to the surface of the food which subsequently causes liquid to leech from the item and alters the texture.
With that as background I wanted to see if there was any discernible difference in a food product vacuumed at a level which would allow the surface of the item to boil vs one which was not. I also wanted to see if re-packing an item originally vacuumed at a level where the surface would boil and then re-packing at a lower pressure would have any impact.
So this is what I did:
I used 3 nearly identical chunks of chicken breast each cut from the same breast. Each piece was 50g.
I bagged 2 at 99%+30sec and the third at 80%.
I opened then re-bagged one of the 99% pieces at 80%.
For the 2 pieces at 80% I added some glass marbles to the bag to make them sink.
The 3 samples were cooked at 60°C for 1 hour then chilled in an ice bath.
I unpacked each sample, dried them off and weighed them. There was no appreciable difference in weight - my kitchen scale only has 1g resolution so if there was a change it was less than that.
I cut each piece through the middle to see if there was any noticeable difference in texture and could not detect any. I did photograph the results but the photo doesn't show anything useful.
I cut a small slice from the middle of each sample and tasted it. Both the flavour and texture were identical - or at least close enough that my palate could not discern any difference.
So what I've learned is that (at least for chicken breasts) you can vacuum to any pressure with impunity.
As for Dave Arnold's observations all I can say is that things must be different in the northern hemisphere compared to here in the Antipodes! We know that water swirls down the drain in the opposite direction so what else is different?
Cheers,
Peter.
(Edited because I forgot to reference Modernist Cuisine)
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....., but also to move a lot of air (6.5 CFM). So it'll make a damn quick evacuation, but only about normal for a commercial unit I think in terms of strength.
I have a Henkelman Boxer 42 unit which is a large table top commercial machine. It's pump according to the spec. pulls 21m3/h which equates to 12.3CFM or nearly twice as fast as your pump. The cycle time for my machine is 15-35 seconds and the best I can calculate the volume of the chamber is that it is something less than 1.2cf (or 0.03 m3). If my calculations are correct it should vacuum in around 6-10 seconds which seems about right then allowing a couple of seconds for sealing and a further few for soft air introduction the stated cycle times seem about right. I notice that it takes much longer to pull the last few percent of vacuum than it does to go from 0-80%, so I don't think that you can just calculate the time using only the volume of the chamber and the vacuum rate of the pump.
What size of the chamber are you planning to vacuum? If it is too large you may find that a 6.5cfm pump takes a while to get there.
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hmm, it's certainly a lot more mistakes than I would have expected in this kind of work, especially in the recipes. I don't care about a misplaced comma or misspelled word, but wrong numbers in a recipe are really not good and I'm a bit dismayed by seeing so many errors here. Maybe it's a good thing I kept the box, maybe I'll buy a 2nd printing and sell the first printing to a collector
Actually, it would be neat if we could at least somehow obtain a correct kitchen manual down the road, at this high price and with such involved cooking, a wrong number can cause complete failure of a potentially expensive and time consuming dish....
It is great they are on top of it and post errors online, but the idea to mark up my expensive books with pencil (and who knows what works on the kitchen manual pages) is extremely unappealing to me.
So far it seems that 112 errors are listed for the kitchen manual. I have not looked at all of them to see if they are real errors (g for mg, 3 for 5) or just grammar etc. It would be great if the real fatal to a dish errors could be highlighted somehow.
I agree
I don't really want to mark my copy of MC - it seems like sacrilege to take a pen or pencil to such a beautiful work. I agree that a few typos are not a great concern but anything material like a quantity, ratio or temperature is very important. For me having an accurate Kitchen Manual would probably suffice - preferably a new one with an index as well.
Maybe the MC crew could offer a trade in on our original, but incorrect kitchen manuals. If not a trade in - perhaps the ability to purchase the V2 version after providing proof of purchase of the first printing.
Cheers,
Peter.
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Finally got hold of mine, after a long day at work and 30 minutes carefully unpacking the tomb, didn't have chance to thumb more than 10 of the 2500 pages.
Anyone any idea where the ultrasonic chips are and the chicken with the golden brown skin that was cooked sous vide? (I think they cooked the skin in peking duck kind of way). And the bullet proof Bernaise sauce?
..............You can see what's first on the menu.
Sounds like you're after an up-market KFC experience
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Definitely agree: The more I understand the chemistry, physiology, and physics of what happens in the kitchen, the less I rely on recipes for anything more than a starting point (sometimes, I'm just inspired to try something suggested their titles): The more I cook, the more what I put produce is 'me' (although frankly, I think a lot of so-called 'individualism'/'self-expression' are not actually unique, though we like to think they are.)
Couldn't agree more. Understanding the how what and why of as yet untried techniques makes me much more likely to attempt them. When I first became aware of Nathan's sous vide book I wanted one - primarily because there were very few books on the subject and some (most?) of those had information which was suspect and at the very least the books didn't agree with one another. Thomas Keller's Under Pressure for instance suggests cooking temps much higher than I have found acceptable from my own cooking experiments. I gained much more useful information from the SV thread here on eG particularly those from Nathan and Douglas Baldwin.
Once the SV book morphed into the MC opus I became even more interested as snippets of its content were revealed. I've now had my copy for a few days and after browsing all the volumes I've decided to go back and start from page 1.1. There is too much information to miss if you only randomly access it - serial processing is called for
. That said the book(s) is(are) set up very well for random access if you are looking for something specific.I have printed a copy of the .pdf index (after a small hack) and have that with me so I can easily cross reference as I am reading. It is also good to scribble on - something I cannot bring myself to do to the original work.
I never really expected MC to be a cook book with recipes to slavishly follow. I expected a work which explained and displayed the science behind the various techniques and I have not been disappointed. In my opinion MC is like a post graduate course in cookery. Nearly every method (pastry chef magic aside) is explained and I have learned things about subjects I thought I knew well just from my initial browse.
I'm now just trying to manufacture enough spare time to get through the 2.5K pages!
Note to Nathan - It's better than I expected even given high expectations.
Peter.
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PS @blackp: Regarding Beef Wellington, why use liverwurst? Maybe you have got better liverwurst, but I'd rather make the duxelles for Wellington without any liver than use a pork or veal sausage. But then again I have a somewhat irrational dislike for commercial forcemeat sausages – probably some repressed childhood trauma ;-)
I've never used actual pâté de foie in my Wellingtons, but when I substitute for this ingredient, I use chicken liver sauteed with some shallots and white wine (blended of course).
I'm glad your dinner was a success - I guess I was just pointing out (not very clearly) the difficulty in cooking in an uncontrolled water bath which is probably more difficult than conventional cooking which we have learned a feel for over the years.
As for the Wellington - the use of liverwurst comes from my mother's recipe. I've made it with home made chicken liver parfait which I also like, but as a child Mum would make beef wellington for special occasions and it is the memory of that which still works for me.
Of course she never had sous vide to help her and relied on the correct level of cooking during the sear to get the final dish to the table done perfectly. It's much easier for me to get it right than it was for her.
Cheers,
Peter.
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I don't know what type of labels MC used, but I have had good results using paper tape labels and a Brother QL-570 printer. The printer attaches to a PC or mac by USB. Unfortunately the supplied software for the mac is not as good as that for the PC, but for simple labels (say 3 lines of text) the shortcomings are not a problem. The continuous paper tape labels (DK-22205) work out pretty cheap - one roll is over 30 metres long and each label at the size I make them is only 28mm so I get well over 1000 labels per roll of paper tape.
I find that the self adhesive glue does not come unstuck at SV temps or times - the only problem if you can call it that is that the print fades a bit with long/hot cooking although it can still be read after 48 hours @ 57C.
Cheers,
Peter.
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I agree - that Chinatown doesn't look like anywhere I can recall in Sydney.
The plot thickens.....
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Why attempt such a risky method to serve 12 dinner guests?
There are many excellent ways to cook fillet steak conventionally.
The whole deal about sous vide is accurate temperature control. Without that you have hit and miss. You may cook a great meal for your dinner party or you could just as easily make a mess of it - with no particular explanation as to why given the degree of control you have over the cooking temperature.
My recommendation is to find a conventional recipe for your fillet and purchase a suitable sous vide device to enable you to experience things cooked to precise temperatures.
I've made excellent Beef Wellington using eye fillet after cooking it at 50C for 2 hours and then coating it with liverwurst, mushrooms and finally wrapping it in pastry and baking it. Using conventional methods it is very hard to get the meat cooked sufficiently without overcooking the pastry, but given that my meat was already properly cooked to rare it did not over cook and I took it from the oven once the pastry was done to my satisfaction.
I use a Sous Vide Magic with a large rice cooker and have had hundreds of excellent meals from that set up.
Cheers,
Peter.
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I agree that the photo looks like Aussie bush, but the blogger is not me!
Cheers,
Peter Black, or blackp or peterb - it all works somewhere!
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What a releif! DHL just called and my parcel was 21kg not 10 as advised by their operator earlier today. Whilst I had seen Chris' photos of the packaging it needs to be seen to be believed! My set has just travelled 28,000km from China to Canada and then to Australia. Although there is minor damage to the external box the books and their perspex case have survived and are in perfect condition.
Seems to me that the weekend is now officially cancelled!
Cheers,
Peter.
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Mine should be here either later today or worst case on Monday.
The DHL site I can see has no shipping weight so I called the local office who told me that my parcel was 10kg - now I'm worried!
Friday, April 08, 2011 Location Time
16 Processed at SYDNEY - AUSTRALIA SYDNEY - AUSTRALIA 09:24
15 Clearance processing complete at SYDNEY - AUSTRALIA SYDNEY - AUSTRALIA 09:20
14 Arrived at Sort Facility SYDNEY - AUSTRALIA SYDNEY - AUSTRALIA 08:24
Wednesday, April 06, 2011 Location Time
13 Departed Facility in LOS ANGELES GATEWAY - USA LOS ANGELES GATEWAY, CA - USA 11:04
Let's hope it's just a clerical error.
Cheers,
Peter.
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Steven, have a fantastic trip - unfortunately you won't have time to sample much more of what Barcelona has to offer. I was lucky enough to visit there dozens of time for work some years back and fell in love with the place. We've been back several times on holiday since and have good friends there. La Boqueria is a must if there is any time - I've often thought that with unlimited resources I'd spend some part of every year in Barcelona so long as I could have an apartment with decent cooking facilities within walking distance. Unfortunately most city dwellings are very short on kitchen space but the result is the vast number of fantastic places to eat on the street. I guess you can't have it all ways.
In any case even with a small sample of Catalunya under your belt - I'd be surprised if any dedicated foodie didn't return.
Again - enjoy as I'm sure you will!
Cheers,
Peter.
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I've got a DHL tracking number so I'm a happy camper!
Not sure exactly where in China the printing was done, but assuming somewhere near to Shanghai the trip from there to Vancouver to Toronto to Sydney is going to be about 28000km - almost 20,000km more (or 3.5 times the distance) than if it was shipped to me from the source! Sounds like a business opportunity for someone to advise Amazon especially considering that each set weighs in at around 20kg.
According to DHL my books went from Toronto to Hamilton (also in Ontario) then on to Cincinnati and at last look they've left there bound for points unknown en-route to Sydney.
I'm getting impatient!
Cheers,
Peter.
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It's nearly 12 years since I was there and I hadn't yet developed the habit of photographing the food, but here are a couple of the kitchen...
I hope you enjoy it as much as we did.
Cheers,
Peter.
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Amazon Canada's still showing 14 April for me (ordered October).
Can my stress levels survive this? I'm sure it's worse than the approach of Christmas for a six-year-old.
Ditto - ordered October - Amazon.ca still shows 14 April.
Let's hope that these are among the first (only?) 250 en-route by slow train.
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Has anyone seen there is a new circulator from sousvidesystems.com. Their website isn't done yet but they have a facebook page. I think it only went on sale this month and is only $499 + shipping. Their facebook page is not very detailed so I emailed them. The guy who answered said he is heating a 20 gallon bath and holds temperature to within 1 degree. I would take the plunge but I am hoping that someone reviews it first.
One degree doesn't sound very good to me. I can hold a tank within 0.1 degree using my Sous Vide Magic for way less than $500!
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This ever happen to anyone?
I made some salmon a while back. Cooked (followed Dougs book temp/time), quick chilled, and then froze. A few weeks later I put the salmon (frozen) in the SVS at 130F for about 90 min.
The salmon ended up sticking to the inside of the bag. I don't recall that ever happening before. Although the salmon wasn't bad, I was so bummed because most of it ended up shredded that I think it may have "damped" the taste (to me). Anyone have any ideas? Is it because I froze it? Could I possibly have overcooked it? My wife LOVES salmon so I would love to be able to make some and keep it frozen and just do a "heat and serve". I realize this is not the best approach for absolute quality, but the ability to do this sucessfully would go a long way to being able to make a quick and healthy meal. Did I mention my wife loves salmon? ;-)
Todd in Chicago
Why not do it the other way around? Most oily fish freezes well and can be defrosted in the microwave if time is important and cooked SV to order.
I usually buy a whole side of salmon, portion it, vacuum bag it and then freeze it.
I have even tried fresh bought and defrosted portions at the same time and have not been able to detect any significant difference.
Cheers,
Peter.
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I don't know anything about the machines you have but using the kind of bags common to chamber machines sealing is not a problem. Foodsaver type bags are temperamental and don't seal well if there is any food residue, but the non-channel type bags are much more forgiving. As I mentioned up-thread, my machine has one seal element and one cut-off element and I have never had a seal fail in 6 or 7 years.
Give your machine a go without double sealing - bag some rags if you don't want to risk some food, but I'm sure that the good sealing is as a result of the bag type, not the machine.
Cheers,
Peter.
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I wonder how long it would take to get a Bradley delivered!
My BBQ has a smoker tray with a burner underneath so hot smoking is easy for me. I've been interested in cold smoking for a while, but never made the move. Maybe when my copy of MC turns up I might make the leap.
I just checked the Bradley web site - the 4 shelf digital in the US is $500 and here in Australia it is $825 (USD=AUD at the moment).
I can't understand how a 240V conversion could cost >$300.
Might just go for Chris' Ghetto 4000 instead.
Cheers,
Peter.
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For those with problems about bag creep - do your machines have an adjustment which allows the gap between the sealing bar and the pressure bar (inside the lid) to be altered?
If so make it snug, but not tight and it will exert enough pressure to hold the bag in place without it moving around.
Cheers,
Peter.
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They started to offer a quick stop H2O sensor that shuts the vacuuming off when the contents start to boil.
Hmmm - I wonder if it is available as an upgrade? It sure sounds pretty useful.
Could this be the catalyst for more SV investment?
Don't tell the Missus!
Cooking with "Modernist Cuisine" (Part 2)
in Cooking
Posted
Be careful with Activa. Once it's opened and exposed to air it degrades fairly rapidly (or at least that's what they say). I keep my opened pack vacuum sealed and in the freezer as per Ajinomoto's recommendation.
I have read (on another eG topic) that some people report decent shelf life for opened packs, but I've not heard of keeping it at room temperature, and I don't want to waste any by trying it out.
Cheers,
Peter.