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

[hll]

Great correlation between expected and actual results in the sous vide model!

[adey73]

Brilliant.

Until someone put the Wired article up, I had Nathan down as enormously generous fella with the same obsession as the rest of us. But to discover he's also an exuberant polymath puts my faith back into humanity and , ahem, Americans.

Anyway, everytime he posts I find myself looking at new bits of kit. (got the Extech dual Thermometer he recommended).

That Turbochef also looks fantastic, he could start selling equipment like the guy off the old Remington Ads.

[pounce]

One thing I noticed is that I seem to always be doing the ghetto version of things...

In the video he shows a centrifuge and mentions it clarifies stock. Here is my version @ £120. I also dries jeans very nicely

http://www.creda.co.uk/macro/productprint....r=261&prmenbr=2

adey73, do you have the needle probe for the thermometer? Do you use it during the cooking time? I'm curious what you are using the plug the hole you make.

[adey73]

i use this stuff in black.... http://www.tapes-direct.co.uk/index.php?ma...products_id=731

And use two of these during cooking time (cheapest I could find in the UK) http://www.tomsgadgets.com/products/details.aspx?pc=KP180-51

Are you really in Cuba?!

[DouglasBaldwin]

Great correlation between expected and actual results in the sous vide model!

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Yep, even the linear heat equation does a surprisingly good job. Just for fun, I measured the core temperature of a 27mm thick piece of Mahi-Mahi (in a 131F {55C} water bath) every 20 seconds and compared it with my numeric calculations.

In the plot, I used a thermal diffusivity of 1.24 mm^2/sec and a heat transfer coefficient of 1000 W/m^2-K (since I used a circulating water bath). The blue line is the surface temperature of the Mahi-Mahi, the red line is the predicted core temperature and the blue dots are the core temperature as measured by a ThermoWorks MicroTherma2T with a needle probe.

In my guide I use a thermal diffusivity of 0.956 mm^2/sec so that I am 97.7% confident that my predicted temperature will be lower than the measured temperature. I also use a heat transfer coefficient of 100 W/m^2-K since many people use naturally (rather than forced) convection water baths.

[nathanm]

I have done similar charts - it is amazing how close one can get....the mathematical model matches reality very well indeed.

[Silly Disciple]

In the plot, I used a thermal diffusivity of 1.24 mm^2/sec and a heat transfer coefficient of 1000 W/m^2-K (since I used a circulating water bath).  The blue line is the surface temperature of the Mahi-Mahi, the red line is the predicted core temperature and the blue dots are the core temperature as measured by a ThermoWorks MicroTherma2T with a needle probe. 

In my guide I use a thermal diffusivity of 0.956 mm^2/sec so that I am 97.7% confident that my predicted temperature will be lower than the measured temperature.  I also use a heat transfer coefficient of 100 W/m^2-K since many people use naturally (rather than forced) convection water baths.

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That's quite cool indeed. How did you arrive at the thermal diffusivity numbers? Is this out of a table of td numbers for different materials/substances/etc, or did you calculate it based on the empirical curve?

[DouglasBaldwin]

That's quite cool indeed. How did you arrive at the thermal diffusivity numbers? Is this out of a table of td numbers for different materials/substances/etc, or did you calculate it based on the empirical curve?

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For the Mahi-Mahi, I used thermal diffusivity as a fitting parameter (that is, I calculated it from the measured data). Even if had found the thermal diffusivity in the literature, I would expect it to vary from fish to fish and species to species; much of this variation comes from differences in fat and water content.

This variation in thermal diffusivity is the reason why I tabulate the `worst case' cooking time in my tables instead of trying to predict the actual cooking time (as Nathan does). That is, if the water bath is just above the desired final core temperature, I am assuming it is much less of a sin to cook the meat longer than needed than to not cook it long enough*. While this assumption seems reasonable for most meat, I have begun questioning its validity for fish --- often when I cook fish based on my cooking tables, I find that they come out mushy because the fiber-weakening enzymes are still very active at my desired final core temperature (~120F/50C). Without a good source for the thermal diffusivity of fish in the literature, it will take me quite awhile to determine the range of thermal diffusivities in fish experimentally.

* This is especially true if the meat is being pasteurized, since underestimating the temperature of the meat would result in food which hasn't actually been pasteurized.

[MikeTMD]

Does anyone have first-hand experience of veal liver SV? What temperature should it be brought up to?

[FastTalkingHighTrousers]

I sv lamb liver. I cook it to 130F then blowtorch it

[MikeTMD]

Look what I found - both waterbaths are very reasonably priced:

http://www.aibltd.com/detail.cfm?autonumber=47019 and

http://www.aibltd.com/detail.cfm?autonumber=69076

Edited June 16, 2008 by MikeTMD (log)

[MikeTMD]

All right - I just finished my lat night SV dinner:

Veal Liver - cooked to 140F/60C for 40 minutes + demi glace + caramelized onions + duck fat fries ( not healthy, but so good!)

140F cooks veal liver to perfect medium, leaving a touch of pink color - liver solidifies very nicely, and is a lot easier to handle after cooking. I prefer my liver on somewhat medium-rare side - I would like it at 130F, but it's a very personal choice ( regretfully, most wouldn't touch liver no matter how it is cooked). I suspect high heat and clarified butter would be a better way to caramelize veal liver after cooking, although medium heat/non-stick griddle is acceptable.

Veal liver vs/ foie: foie should be SV at higher temps (Broca recommends 140F), and would brown nicely on medium-high heat, whereas veal liver is fairly lean, and as such calls for lower temp range.

Edited June 17, 2008 by MikeTMD (log)

[e_monster]

What would the proposed application of the baths bet? Unless I am misreading the specs, the capacity seems to be only 2 liters which doesn't seem like it would be adequate volume for most sous vide application.

Look what I found - both waterbaths are very reasonably priced:

http://www.aibltd.com/detail.cfm?autonumber=47019 and

http://www.aibltd.com/detail.cfm?autonumber=69076

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[MikeTMD]

What would the proposed application of the baths be? Unless I am misreading the specs, the capacity seems to be only 2 liters which doesn't seem like it would be adequate volume for most sous vide application.

2L capacity is large enough for 2-4 individually packed 8oz portions, isn't it?

[e_monster]

That would leave a pretty small amount of water relative to what is being cooked which makes keeping the temps stable tricky when the food is first added. When I am cooking small amounts of food (i.e. one or two chicken breasts or a 12 oz. ribeye), I use a 6.5 quart cooker (three times the volume of a 2 liter cooker) and wouldn't really want to use less water than that -- otherwise there would be a pretty significant temperature drop as soon as you add the items.

I would think that for anything other than eggs, one would want 6 or 7 quarts/liters minimum.

Anyway, that is my take. And, I might be wrong.

Anyone else have thoughts about this?

What would the proposed application of the baths be? Unless I am misreading the specs, the capacity seems to be only 2 liters which doesn't seem like it would be adequate volume for most sous vide application.

2L capacity is large enough for 2-4 individually packed 8oz portions, isn't it?

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[MikeTMD]

Last night I SV large shrimp ( w/heads, shells, claws - everything) - I had to triple bag those ( claws are very sharp), so, although there was no air in the bags I ended up with a lot of unnecessary "insulation", and as such had to adjust temps to 50C. Fairly speaking, that was barely enough to cook shrimp to rare.

So, lessons learned:

- shell-on shrimp requires higher SV temps

- when cooking shell-on shrimp thermometer/temp reading is essential

- three bags create an extra heat barrier, so SV T/time s/b adjusted accordingly

[jaymer]

Took a big packer choice brisket and separated the point and flat, plus trimmed most of the fat off the fat side. Normally, BBQ folk would trim it to 1/4 inch thickness of fat before going on the smoker, but since I knew that fat wasn't going anywhere, I trimmed as much off as I could.

Trimmed the brisket into smaller pieces that would fit in my 8x12 vac. bags.

Browned all but 1 piece in a skillet w/oil. Meat turned gray, with a tiny bit of brown. Didn't want to cook it too much. Seasoned with the same rub (salt/pepper based) that I normally put on Brisket for the smoker.

Put 5-6 bags on a sheet pan then into my warmer oven which is normally at 150. I kicked this up to 160 from 8pm to 8am, then back to 150 during store hrs.

There was one piece of point meat that I mis-trimmed. So I had a very thin piece of point meat that I tried after 40 hrs. That piece was pretty incredible - kinda like a pounded piece of veal.

One thing I thought was interesting was that this thin piece of fat wasn't even tender enough to break and would support the weight of this piece of meat. If that was cooked to 195 on a smoker you wouldn't even be able to grab it (or barely grab it and it would break).

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Here's the 1st piece of Brisket Flat at 47 hrs. Yummy au jus outta the bag. I took this off heat (was 150) and cut into right away - I would think I could have let it rest a bit and it might have sucked some moisture back into the meat. I had some friends come into the store and had an idea to share this with them, so didn't have the time to let it rest. I thought it was a bit dry, but they liked it.

Here's what it looks like sliced.

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There was one more piece of browned flat. Here it is, alongside 2 slices of smoked brisket. 48 hrs.

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And now the final piece that was not browned in a skillet NOR browned after removal from the bag. I did let this one rest 5-10 minutes on the counter. Sliced it up and poured au jus back over it on the plates. VERY yummy. Peppery from the rub... very enjoyable. Stayed together as slices (didn't crumble) and I'd just flip a slice down into the juice and cut it with the fork. Another good friend shared this with me and we both loved it.

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CONCLUSIONS

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One reason I cooked this at such a high heat 150/160 was because of this article:

From : http://amath.colorado.edu/~baldwind/sous-vide.html

Tough Meat

When cooking tough meats, two processes are of particular importance: the dissolving of collagen into gelatin and the melting of solid (saturated) fats.

Before sous-vide cooking, the dissolving of collagen into gelatin required cooking meat well done (between 160°F/70°C and 180°F/80°C) and holding it at that temperature for a couple of hours. The reason being that while collagen begins to dissolve at 131°F (55°C) [Thi06], it must be held at that temperature for 12--72 hours to have a significant effect---something impossible to achieve with conventional cooking methods. However, thanks to sous-vide's precise temperature control, it is both possible and quite common to cook tough cuts of meat for 24--48 hours at 131°F (55°C).

While collagen will begin to dissolve at 131°F (55°C), only 5--10% of the saturated fat in pork and beef will melt at that temperature. Nearly 60% of the saturated fat in pork and beef, the saturated fatty acid palmitic, melts at 145°F (62.8°C). The remaining 30--35%, the saturated fatty acid stearic, melts at 157°F (69.6°C). So in order to melt the saturated fat in pork and beef, it must be heated either above 145°F (62.8°C) or 157°F (69.6°C), depending on how much of the fat you want to melt.

The 2 paragraphs talk about 2 cooking ranges... 131 (which several people have done, including the beef ribs) and the higher temps to melt saturated fat. Since my personal trainer would normally want me to stay away from beef DUE TO saturated fat, I thought this test would see what happens if this PALMITIC and STEARIC was removed from the meat. Only problem is to determine IF IN FACT saturated fat was indeed removed. And from close up pictures of the flat slices, you can see there's plenty of connective tissue still in the meat. Any most telling to me is that this morning in my home kitchen was a 1/2 pan with all the au jus from the last bag of brisket. I fully expected it to be congealed fat (75-78 deg room temp) but it was almost yummy enough to drink. There was just a tiny thin scum layer on the top but nothing that resembled cold grease. If it (the fat?) wasn't in the bag, then was it still in the meat?

We cook an already awesome smoked brisket AND beef short rib on our smoker, so I don't see much value in using sous vide for these meats. I'd like to try more brisket flat at a lower temp just to experience that. It would be nice to hear from anyone who has an idea as to the fat issues.

More pics available directly from my gallery section:

http://www.jaymer-que.com/gallery/?Qwd=./B...umbs&Qis=M#qdig

jaymer...

[MikeTMD]

Put 5-6 bags on a sheet pan then into my warmer oven which is normally at 150. I kicked this up to 160 from 8pm to 8am, then back to 150 during store hrs. 

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jaymer,

What type of SV equipment do/did you use for your brisket?

[MikeTMD]

Well, my favorite buffalo vendor was not at the Farmer's Market today, so the "only" other choice was bison from Twin Valley Farm in Wisconsin.

I opted for tenderloin, primarily because of the smaller cut size ( and as such - lower total cost), as well as perfect SV-ready packaging. The vendor lady warned me that bison cooking time would be about half compared to similar cuts of beef, she also said: "... if you overcook it - you ruin it". I explained that I would cook the meat in the vacuum bag, at a very low temperature - she appeared a bit confused: "I never heard of anything like that..."

I cooked the tenders at 60F for about 20 minutes, and held them at temperature for another 10 minutes - just enough to reduce veal stock to lucious demi, then seasoned the meat and seared it at high heat for 20-30 on each side before plating.

The texture of bison tender cooked SV is incredible - it is, literally, as soft as a marshmallow. Will make again anytime.

NB: 60F - medium-rare, more on the rare side - I don't know if bison tenders could sustain temperature any higher than that, without loosing juiciness and taste.

Edited June 30, 2008 by MikeTMD (log)

[Sartain]

Hi all:

I'm just getting into sous vide and this thread is really informative. I have two questions that I need some help on:

1) I noticed that on Nathan's tables the rest times seem to vary from a few minutes to close to an hour. In conventional cooking, I would interpret rest time as the time out of the oven/skillet/grill etc. For example, For a 1.18 inch thick piece of meat cooked to a core temp of 60C, according to the table the cooking time is 54 minutes 28 seconds and the resting time is 54 minutes 29 sec. So, am I supposed to pull the bag out after an hour and let it rest for an hour? Or should I be doing something different?

2) In searching this thread I saw the recommended temp and time for lamb loin is 55C for 2-3 hours. Is that cook and serve? If I were to cook it for 3 hours, ice for an hour and refridgerate, how long can I hold the loin until I serve it?

Thank you for any advice you can throw my way!

[MikeTMD]

... In conventional cooking, I would interpret rest time as the time out of the oven/skillet/grill etc.  For example, For a 1.18 inch thick piece of meat cooked to a core temp of 60C, according to the table the cooking time is 54 minutes 28 seconds and the resting time is 54 minutes 29 sec.  So, am I supposed to pull the bag out after an hour and let it rest for an hour?  Or should I be doing something different?

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Sartain,

I believe nathanm defined "resting time" as the period during which internal temperature stops rising and begins to fall, so it's really plateau time rather then resting time. You don't have to let your cooking bag sit for an hour after SV poaching, in fact I would strongly advise against it for Food Safety reasons - you choices are to serve immediately, or to cool your cooking bag rapidly, and refrigerate till service.

As far as how long to keep your SV bags refrigerated prior to service - you will hear a wide range of opinions on this matter, primarily because there isn't a magic number. Personally, I would be equally comfortable with 24-48-72 hour span, but, again, there will be other suggestions.

[Sartain]

Food Safety reasons was precisely what gave me pause. A prolonged "rest" didn't make sense to me and I thought that maybe it should be a combined time (cook time + rest time = total time in bath). I guess that's not it either.

[nathanm]

I believe nathanm defined "resting time" as the period during which internal temperature stops rising and begins to fall, so it's really plateau time rather then resting time. You don't have to let your cooking bag sit for an hour after SV poaching, in fact I would strongly advise against it for Food Safety reasons - you choices are to serve immediately, or to cool your cooking bag rapidly, and refrigerate till service.

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Yes this is exactly it.

The only reason to have it rest is if you use a cooking bath temp that is much hotter than the final temp. Then you need to remove it and let it rest to allow the core temp to come up. But frankly this is a silly way to cook in most cases.

[MikeTMD]

Food Safety reasons was precisely what gave me pause.  A prolonged "rest" didn't make sense to me and I thought that maybe it should be a combined time (cook time + rest time = total time in bath).  I guess that's not it either. 

No, it's not. :-)

My personal preference is to cook for immediate service at home, which is opposite to what I'd do in a commercial environment.

What kind of SV set-up do you have?

Edited July 1, 2008 by MikeTMD (log)

[Sartain]

I've got a Polyscience immersion circulator, which I hook up to a lexan tub. I'm relying on good ol' Foodsaver for now - can't afford a chamber machine yet. I did some chicken breasts tonight with some herbs, carmelized onions, gelled stock and butter. Didn't do the finishing step because I wanted to get that pure SV taste and texture sensation. Not bad - pretty tasty actually, but I would probably have preferred a quick sear at the end.