Sous Vide: Recipes, Techniques & Equipment (Part 2)

[slkinsey]

The reason lab heaters circulate the water is to maintain all the water at the same temperature.

Do sous-vide cooks (I'm not one) routinely use the circulating type?

Yea. As far as I know, most everyone who uses a water bath for sous vide cooking uses a recirculating type. Otherwise, how can you insure uniform temperature rthroughout the water bath? I do mine in a 5 gallon vessel, and assume there would be significant challenges to hitting/maintaining a target temperature with +/- 0.5C (mine is good to <0.1C) unless the water were circulating.

On the other hand, someone like nathanm would have a better answer on this than I.

The thermal circulating units (maybe including that Lauda?) are very precise, but more expensive, starting around $700-800 depending on size.  The other type is a regulated water reservoir without circulation, starting around $350.

Seems like you can find recirculating units for around $400 bucks or less on eBay if you're lucky. I got my Lauda, thoroughly cleaned and reconditioned, for something like $500. Brand new units go for significantly more.

I think the very nature of the way [a crock-pot] heating element works would likely cause the temperature to overshoot with some frequency, and the temperature would likely swing with a range of several degrees.

Sam and also jackal10, that may or may not be relevant (do you have data?)

I'm just thinking in terms of practicalities. As you say, almost every feedback-regulated temperature controller in daily life employs an on-off heating element. My Lauda does not appear to be different in that respect. Once the Lauda reaches the target temperature, the heater appears to pulse on and off as the unit determines necessary to maintain the target temperature. The entire water bath is the same temperature, because the water is constantly recirculated.

Consider now, a crock pot. First of all, it would have to be a gigantic crock pot in order to hold enough water for anything bigger than a few pork chops at a time. So, you've got a temperature probe in the middle of the water bath. The heat element comes on full blast and heats up the Crock Pot's ceramic insert. Eventually, the water around the probe reaches the target temperature and the heating element shuts off. But, of course, it doesn't suddenly go to zero heat. How long does it take for the heating element to cool down? How long does it take for the ceramic insert to cool down? Presumably, the ceramic insert and the water near the ceramic insert are already warmer than the target temperature once the water next to the probe reaches the target temperature. So, what happens is that the residual heat in the heating element and the ceramic insert conduct into the water and the water overshoots the target temperature.

I suppose that you could theoretically hit a point where the heating element was pulsing on and off just the right amount (assuming the heating element is amenable to that sort of thing) to maintain the target temperature at +/- 0.5C. Maybe. Or it could just continue to swing back and forth too much to be useful for the full range of sous vide techniques, some of which are more temperature-sensitive than others. But I still have to believe that there will be temperature stability, uniformity and accuracy problems when the temperature probe is in a reasonably large volume of non-circulating water, and the heating element is on the bottom and/or sides of the vessel. Of course, there's no way of knowing unless someone tries it.

It might be worth Robert Wright's/Lab-Pro Incorporated's time to do some testing and see if they can come up with a system large enough to do real-world amounts of food that has temperature stability and accuracy within, say, 0.5 - 0.25 degrees C. If they could either produce a system for around $200 or sell a unit with instructions for under $100, I bet people would buy it.

[MaxH]

For any who didn't see Lillian Huang's May-16 letter with caution and further source referrals (following the Tara Duggan sous-vide article in SF Chronicle), it's on the letters page linked below. (I just pass it on, I won't presume to second-guess it.)

SFgate Link

[MaxH]

... the Grant Instruments sous vide tanks ... It appears that they have done the engineering quite well .. thermal convection instead of a circulation pump, heater on the bottom to drive the convection (vs on the side as with a crock pot) ... The price point for a mass market sous vide system is probably around $300, which means that it needs to cost less than $60 to make which is quite a challenge if you have any custom parts.

Maybe not so hard, if the autoconvection provides enough circulation, as those comments imply. (A core issue here: Much of this recent discussion has implicitly been about whether or not an explicit circulation system is needed.)

I didn't know all crock pots heated from sides, but they don't fundamentally need to, and anyway I have an east-Asian rice cooker and a kettle-type corn popper, both pots with heating elements below. All these simple appliances sell for circa $20. The accurate lab temperature-regulating power-control module I was shown was around $90 (including an accurate sensor on a cord, and a presumably microcontroller-driven servo control algorithm). By my arithmetic this makes $110 retail. Presumably one of these firms could integrate the components.

That also assumes a moderate size for home use, and that autoconvective circulation together with the water properties and control algorithm maintain food temperature stable enough for sous-vide cooking (or that adding a circulation impeller of some kind is inexpensive.)

'Optimal control' and bang-bang controllers?... I never thought it would be used in cooking!

My point is that arithmetic-intensive algorithms inconceivable in consumer products 15-20 years ago are now routine. It's is what digital hardware does best, with decreasing cost. Computations inside a CDMA cell phone or a modern TV with 2-D digital filtering would have challenged NASA in 1985.

... optimal controllers are often bang-bang controllers.  This fact can play havoc with the results in the elementary theory of differential equations!!

Tell me about it. (I dealt with that same havoc in a different application area.)

Fundamentally, and conveniently, controlling temp of a water pool has the inherent format the control engineer classically seeks in any regulator. The dominant pole [time-delay element] is at the output [i.e., the water thermal mass.] So the water itself provides a local reservoir of heat, available directly and intimately to the food. Unless the time constants in the food are long compared to that of the water, or the cooking time is short, the whole configuration, including food, tends to settle naturally toward whatever temperature the water is regulated to. Convection (natural or with a circulation motore) merely helps this along.

[slkinsey]

I'm interested as to what we think would be the minimum practical volume for a home water bath for sous vide, and I suppose we should divide it into two categories depending on whether the temperature will be equalized throughout the water actively, with a recirculator, or passively via convection.

To my thinking, you'd want to have a fair amount of space around the food, and in particularly between the food and the heat source, when using water bath that is equalized by convection. With a recirculating water bath, should be less of an issue (especially if the heating element is in the recirculator).

[DocDougherty]

I'm interested as to what we think would be the minimum practical volume for a home water bath for sous vide, and I suppose we should divide it into two categories depending on whether the temperature will be equalized throughout the water actively, with a recirculator, or passively via convection. 

To my thinking, you'd want to have a fair amount of space around the food, and in particularly between the food and the heat source, when using water bath that is equalized by convection.  With a recirculating water bath, should be less of an issue (especially if the heating element is in the recirculator).

←

Ah yes - an interesting point for conjecture. But the minimum volume for what? A retail sous vide system with a tank and heater? Or the size of the smallest tank you want to use with a clamp-on circulator? I think the retail system is designed by the maximum size that somebody can store and carry to the sink to empty - maybe someplace around 40 lbs full or less than 4 gal of water. But with a circulator that can be clamped on the side of a 2-gal spaghetti pot, you can get by with a lot less water when you are just cooking a piece of salmon, maybe 1 gal. But to do three 3-lb tri-tips and have enough room for them without trapping them against the side or bottom, it may take 3 or 4 gal. Probably would want to do a focus group to figure out what the major drivers are perceived to be - but you would need experienced users to get valid results (unless you are interested in what sells rather than what is right).

[jackal10]

Much too large.

Most retail equipment is really small. Think of the size of a crockpot.

The whole thing needs to be less than a foot cube (30cm on a side),

Normally it would only be used to cook two portions, maybe 10 portions as a maximum. If a portion is say 5cm x 2cm x 10 cm (about 2in x 1in x 4 in) or 100 cc then 10 is a liitre, so 2 litres or half a gallon would be adequate and a gallon more than adequate

Cheap and quiet, so well insulated and convection not a recirculator.

If we said a 100W heater then it would come to temperature from say 20C to 60C, a 40C riise in 4000 x 40/100 seconds or about 30 mins, Might be able to use an even smaller heater

Edited August 31, 2007 by jackal10 (log)

[slkinsey]

Jack, I'm not thinking in terms of what will sell in retail for a low price. I am thinking in terms of how to achieve certain goals. In specific, I am thinking about how large a convection-equalized water bath would have to be in order to hit and maintain a target temperature within a range of variation that is less than 0.5C, and also such that the water surrounding the food won't vary more than around 0.25C (e.g., I don't want the part on the bottom to be a degree warmer than the part on the top). I don't see anyont shelling out $150+ for a sous vide system that can only cook two pork chops at a time. I'd say it needs to be able to accommodate at least, say, six double cut pork chops at once or six portions of beef short ribs, etc. -- in other words, something right around the size of an American football. I doubt you could put that amount of food into a bottom-heated, convection-equalized water bath of only one gallon and not have temperature equalization problems. You'd also run into a problem that the volume and thermal mass of the food would be more than the volume and thermal mass of the water. For example, a gallon is 231 cubic inches. Six double cut pork chops would be around 128 cubic inches, leaving only 103 cubic inches for the water. I don't see that working. This size would work for a crock pot, but not for a water bath for sous vide.

Not that I think the size issue is unimportant, which is one reason I favor a clip-on recirculating heater over an all-in-one convection-equalized design. The clip-on unit is small, and you can use it with equipment you already own (you can even clip it to a plastic pickle bucket or rubber bus tub, for that matter).

Doc, I agree that you can use a large variety of vessel sizes when you use a recirculating heater. I'm more interested in minimum practical size requirements for a convection-equalized water bath. And for practical use, as I say above, it should be large enough to accommodate food at least as large as a pork loin, first-cut brisket, short ribs for 6-8, etc. For people who just want to do short-time sous vide cooking in small portions of foods such as two pieces of salmon, a dedicated water bath system really isn't needed. A large stock pot and a highly accurate thermometer should suffice.

Edited August 31, 2007 by slkinsey (log)

[cookingkid]

Not to change the subject, but can anyone provide a source or instructions on how to achieve compressed melon? I have seen it mentioned in a few different places, but I cannot find a place that says how to accomplish it. Is it necessary to have the cannisters or can the compression be done with normal sous vide bags?

Thanks.

[BryanZ]

Bags are fine. Ideally you can pull a stronger vacuum than what a FoodSaver can achieve but I've had decent results with compressed strawberries and watermelon.

[wijit01]

Recently, I did a few experiments. Just an 8 quart AllClad dutch oven on my smallest burner at it's lowest setting. It stabiliized at 140°F.

I used Nathens thickness/time/temp charts to cook ribeyes. Just used a ziploc and squeezed out the air. Took all of 35 minutes, 127° internal temperature.

Blasted it in a smoking saute pan for one minute a side and got a wonderful, tender medium rare steak with a lovely sear. No muss, no fuss.

The ziploc was great because you can check the temp whenever you want.

This is great for me because my challenge is always quick-to-cook, tender cuts and the method really improves the odds by slowing things down.

I'll stick to braising the slow stuff for now, as I'm generally pleased with the results.

I also did shrimp (in a butter and garlic sauce) the same way and it was great. Took about 7 minutes. I judged the color to determine when done.

The method slows things down for those of us who are not too quick witted.

[alwang]

If people haven't checked out Michel Richard's "Happy in the Kitchen", I'd highly recommend it. As a cookbook, it strikes a great balance between interesting new techniques and thoughtfully conceived recipes. One of the methods he makes use of quite heavily is essentially sous vide on the cheap: tightly wrapping foods in Saran wrap and poaching it at controlled temperatures on the stovetop. For the short-duration, relatively high temperature applications he's talking about, I'm sure his methods work fine.

[Msk]

Ronco Wired Controller

Here is a temp controller I use for brewing, it only works in 1 F increments so I am not sure if it works for the most demanding sous vide applications.

However I may try to rig this up with a heater and do a test, maybe using a cooler like I would a mash tun. It can be purchased pre wired so that helps, but you would also need to buy the thermocouple to put in the water bath.

I dont see why it couldnt be used with a crock put with the temp on high.

Msk

[jmolinari]

I use something similar to that Ronco controller for a cured meat chamber, and you have to remember it has a large hysteresis. It'll only cycle ever 4-5 deg.

So if you set at 100F, it'll go from 96-100 or so.

[Msk]

Not that one, it switches on if the temp goes 1 degree below your threshold. I used it to turn on and off a heating pad to keep by fermenting beer at a certain temp during winter in the garage.

Edited to add:

Typically its the analog controllers that have the large threshold gaps often as high as 8 degrees.

Edited September 26, 2007 by Msk (log)

[jmolinari]

Ah good to know MSK. Mine is in fact analog. It is fine for what i do since i think cycling the fridge every degree would be very bad

Hey, where did you find a heating pad that doesn't have a timer built in? The only ones i can find all have a timer so it can't stay on for 24-36 hours that i need!

[Peter the eater]

This thread has been a great source of info for me - thank you all!

I especially gravitate toward the less difficult, less expensive techniques. I have discovered that my very large stock pot will maintain 58-62C on the lowest electric element setting.

Here's what I did:

a very cheap beef roast, vacuum wrapped in a recycled milk bag. Double-bagged actually, and good thing as there was a bit of leakage.

into the 60C +/- bath for five hours.

out of the bath, looks a bit gray on the outside but the fingertip poke test says rare!

cut in half it looks perfect.

I had intended to sear the outside with a hot oil pan or barBQ or torch, but it was so tender and pink it was devoured before I had the chance.

Conclusion: This way of cooking beef is the cat's ass! I feel as though I got a prime rib from a blade pot simmering whatever it was called.

[wijit01]

This is all very interesting! I think the controller in question is actually a RANCO MODEL ETC-111000-000.. Prewired they're $80.00 shipped. Ebay has 'em for $50 without wiring.

It seems that they'll run anything up to 16 amps. Try www.rancoetc.com. I'm not affiliated, I just found them with a google search. I may go for it (I love tools!) and report back.

Beats dropping a grand on new lab stuff or taking my chances with an Ebay bio-hazard.

BTW, while I have a vacuum bagger, ziplocs work good too, real good.

[slkinsey]

What would these controllers be controlling, exactly? Presumably you're not going to wire them into an electric stove.

[jmolinari]

I did a similar thing with a on/off controller with a portable electric eye and a pot of water on top, and it worked OK. If i set it at 130 F it would vary between 128 and 135 or so.

But i didn't experiment too much with it.

[wijit01]

What would these controllers be controlling, exactly?  Presumably you're not going to wire them into an electric stove.

←

They control a heat source. It could be a crock pot or a hot plate or other small appliance.

Instead of plugging the appliance into the wall you plug it into the controller and then plug the controller into the wall. A temperature probe is put into the water that you want to heat to the controlled temperature. The controller then switches on power to the appliance when the temperature is lower and cuts it off when it hits the set point.

The sophistication of the feedback loop and the control logic is why different methods have different results. Lab equipment costs a lot more because it's more precise and that precision costs money. Note the word precision, not accuracy.

The question is how precise one needs to be and it's not all on the controller. How quickly the appliance heats up or cools down has an effect as does the amount of water being controlled and the vessel it's in.

For most the things that I would cook by this method, the precision of a commercial controller should be adequate. It may take some practice and calibration but so does my oven and range.

BTW, you could control a range burner with the Ranco device but it would get pretty ungainly and probably void your stoves warranty .

[slkinsey]

What would these controllers be controlling, exactly?  Presumably you're not going to wire them into an electric stove.

←

They control a heat source. It could be a crock pot or a hot plate or other small appliance.

Instead of plugging the appliance into the wall you plug it into the controller and then plug the controller into the wall. A temperature probe is put into the water that you want to heat to the controlled temperature. The controller then switches on power to the appliance when the temperature is lower and cuts it off when it hits the set point.

The sophistication of the feedback loop and the control logic is why different methods have different results. Lab equipment costs a lot more because it's more precise and that precision costs money. Note the word precision, not accuracy.

The question is how precise one needs to be and it's not all on the controller. How quickly the appliance heats up or cools down has an effect as does the amount of water being controlled and the vessel it's in.

For most the things that I would cook by this method, the precision of a commercial controller should be adequate. It may take some practice and calibration but so does my oven and range.

WRT precision and accuracy... presumably the temperature sensors on these controllers are sufficiently accurate, if that's what you're getting at. I still have a hard time believing that a bottom-heated system or a crock pot system controlled by one of these things wouldn't exhibit temperature variability to the tune of 5-6 degrees C. This would definitely have some effect on certain cooking techniques, and for short-term cooking techniques (e.g., fish) it's not clear that it would have an advantage over using a large stockpot and an accurate thermometer.

[DocDougherty]

WRT precision and accuracy... presumably the temperature sensors on these controllers are sufficiently accurate, if that's what you're getting at.  I still have a hard time believing that a bottom-heated system or a crock pot system controlled by one of these things wouldn't exhibit temperature variability to the tune of 5-6 degrees C. 

←

You are correct that the sensors have little hysteresis and are also quite accurate, but the amount of temperature overshoot that you see in practice is proportional to the ratio of energy stored in the heating system (above the set point) to the energy stored in the water (assuming that the container is relatively light and the food is slow to respond). So if you are controlling a 1200W hot plate and it is heating a pot full of 20 lb of water, you might have 10 to 20 BTU of heat stored in the heating element when the sensor/controller turns off the power (assuming a bang-bang controller). That heat can raise the temperature of 20 lbs of water by only 0.5 to 1.0 °F. If you have the controller set to control to a 1°F tolerance, you have a compatible system. On the other hand if you have a large heater and a small pot of water, you could see larger swings in the water temperature. If you are trying to approach a linear controller performance, you could put a variac or an SCR/triac in the power line to the heater and after it gets up to temperature you could reduce the peak input power. This would mean that the heater will be on a larger fraction of the time, but the water temperature will not recover as quickly from a transient (such as adding food to the pot). Lots of choices. For a convection-driven system, you probably want to have some amount of constant heating at the bottom just to turn over the liquid in the pot.

Doc

[wijit01]

What would these controllers be controlling, exactly?  Presumably you're not going to wire them into an electric stove.

←

They control a heat source. It could be a crock pot or a hot plate or other small appliance.

Instead of plugging the appliance into the wall you plug it into the controller and then plug the controller into the wall. A temperature probe is put into the water that you want to heat to the controlled temperature. The controller then switches on power to the appliance when the temperature is lower and cuts it off when it hits the set point.

The sophistication of the feedback loop and the control logic is why different methods have different results. Lab equipment costs a lot more because it's more precise and that precision costs money. Note the word precision, not accuracy.

The question is how precise one needs to be and it's not all on the controller. How quickly the appliance heats up or cools down has an effect as does the amount of water being controlled and the vessel it's in.

For most the things that I would cook by this method, the precision of a commercial controller should be adequate. It may take some practice and calibration but so does my oven and range.

WRT precision and accuracy... presumably the temperature sensors on these controllers are sufficiently accurate, if that's what you're getting at. I still have a hard time believing that a bottom-heated system or a crock pot system controlled by one of these things wouldn't exhibit temperature variability to the tune of 5-6 degrees C. This would definitely have some effect on certain cooking techniques, and for short-term cooking techniques (e.g., fish) it's not clear that it would have an advantage over using a large stockpot and an accurate thermometer.

←

I agree with you about the stock pot and a good thermometer for quick items (less than an hour) It's how I've done my experiments so far. The thing is that with a 10 quart pot my smallest burner turned as low as it will go, it stabilizes at 140°F.

Using time/temp/thickness charts found on this forum, I was able to cook several thing pretty well. It is also quite low effort/cost (none!) for the good results.

I think the advantage to a controlled system is in longer cooked items like roasts or short ribs. A controlled system would be more convenient.

As the post below suggests, one would have to match the heat source, water volume and controller to each other. Lab systems have already gone through the trouble.

Not exactly plug and play but worth the effort. I'll report results as I find time to experiment.

[inuyaki]

Food & Wine has an article this month about a Napa Valley garden party the features Thomas Keller and his recipe for the famous fried chicken they serve at Ad Hoc in Yountville. I've had Ad Hoc's fried chicken and love it so much, so I was excited that the recipe showed up in the magazine. I made it last night and it was really good, although I did scorch some of the chicken. Still, the chicken was juicy and the crust was crispy, and for a first effort, I thought it went very well.

I was talking to a friend about it this morning and he suggested sous vide. Process the chicken to temperature in the brine and then dredge and fry it at a fairly high temperature to make it crispy. We agreed that the juiciness of the meat would be amplified using this method and a nice contrast to the crispy crust.

Does this sound like it would work? Or would the frying negate the benefits of the sous vide?

[Pielle]

What would these controllers be controlling, exactly?  Presumably you're not going to wire them into an electric stove.

←

The problem with the RANCO controlers is that they are of the ON/OFF type so would definatly have a significant variation in the temp because the controler cant shut off the power until it has reached the target temperature, inevitably causing overshooting. These controlers are better at controlling fridge temperatures for beer making or even charcuterie.

What you want to efficiently controle the liquid temperature over a short or long periods is a PID controler, which uses a mathematical algorithm to can calculate how much heat should be applied to heat to a given temperature without overshooting and then appling constant heat to maintain that temp.

I installed one of those on my electrical range more then a year ago and coudn't be more hapy about it : it was not too expensive, can be used with about any pot and for a wide range of applications. I can use it to make 40 C salmon or to make 72h short ribs and it does not take any space at all.

Here is a link to the post I made about it a while ago. PID modified stovetop

I may seem a bit complicated but it is acutally very easy, and you dont need to cut up anything in the oven wiring (well I did because I was lazy but you dont NEED to..)