Sous Vide, Revisited

In a previous post, I had recommended the 4130 NIST-Traceable Temperature Controller to control the temperature in a slow cooker. Unfortunately, that particular controller has a range that tops out at 60 degrees C / 140 degrees F, which is enough for cooking beef for long periods of time, but not enough for say, cooking duck confit, which for which a sous vide temperature of 80 degrees C is recommended. In addition, the 4130 is pretty expensive; almost $150. It’s possible to add a resistor to change the range of the 4130, but the temperature displayed by the controller is no longer correct, and you have manually create a conversion table between true temperature and the temperature as seen by the controller.

I’ve recently come across a cheaper and better possibility, the Ranco ETC-111000-000 Temperature Controller which is only half the price and comes with a much larger working range (-30 to 220 degrees F). The price with the AC cord already wired in is $75; and the version which just has a 120VAC SPDT relay is only $60.

A bit more about food safety. There has always been a lot of concern about bacteria growth and botulism, for good reason — and so therefore the recommendations for cooking temperature have a lot of safety margin in them — to the point now that the USDA recommends that steaks be cooked to at least 145 degrees F, which is well within what had traditionally been called “medium”, and chicken to at least 165 degrees F, which is enough to really destroy taste and texture. Sous vide cooking, especially some of the more low temperature variants, have raised a lot of concerns, to the point where a few years ago New York City (temporarily) banned it, causing a great outcry in the foodie community, since many top restaurants use sous vide techniques.

First of all, any recommendation about internal temperatures and food safety that doesn’t also factor in time is massively oversimplifying the problem. Here is a table taken from “Food Safety Hazards and Controls for the Home Food Preparer”, published by the Hospitality Institute of Technology in 1994:

Temperature, F Time, 5D kill Time, 6.5D kill
130 86.42 minutes 112.34 minutes
135 27.33 minutes 35.53 minutes
140 8.64 minutes 11.23 minutes
145 2.73 minutes 3.55 minutes
150 51.85 seconds 1.12 minutes
155 16.40 seconds 21.32 seconds
160 5.19 seconds 6.74 seconds
165 1.64 seconds 2.13 seconds

This table lists the time to reduce bacteria concentrations of Salmonella and E. coli from 100,000 to 1 (5D) or 3,162,277 to 1 (6.5D). The FDA and USDA recommend cooking hamburger to 5D destruction. Since it is extremely unlikely for there to be more than 100 Salmonella organisms per gram of meat, a 5D kill will reduce Salmonella concentrations to no more than 1 organism per kilogram. So whether you cook a piece of meat to an internal temperature of 165 degrees for 1.64 seconds, or hold it at 130 degrees for 90 minutes, the effect on Salmonella and E. coli bacteria will be the same.Of course, one concern is that in many forms of cooking, particularly oven roasting and grilling, the temperature of the food as it heats up may not be even; so how do you guarantee that all parts of the food product has been brought up to the requisite 165 degrees? One way that recipe authors, fearful of liability concerns, have done so is to tell people to cook meat to much higher internal temperatures, to provide that extra safety margin at the expense of dessicated, horribly tasting turkey or chicken. But the advantage of sous vide cooking is by immersing the food in a water bath, the excellent heat conductivity of water helps guarantee that the entire body of meat will get raised to desired temperature relatively quickly. (How quickly depends on the thickness of the meat, obviously). So if you hold a roast beef that has been vacuum packed in a Foodsaver bag for five or six hours, there should be no question that all of the common bacteria has been inactivated, and that amount of time at 130 degrees F should be sufficient to inactivate 99.9 percent of all botulism toxin molecules (not there should be any in a fresh piece of meat, of course!)

However, sous vide temperatures are not enough to kill bacterial spores, in particular C. botulinum, which is responsible for botulism. This requires temperatures far in excess of boiling water at sea level. For example, home canning protocols recommend holding the food product at 250 degrees F for at least 15 minutes. This is an issue in the restaurant business because very often food would be cooked sous vide, and then stored in the vacuum sealed bags for potentially weeks (yes, you could be eating an extremely expensive meal at a top-end French restaurant that had been cooked several weeks ago, and reheated just before serving; yummy, no?). If the food packages aren’t cooled quickly enough, and then allowed to warm to the danger zone, it’s possible that in the anerobic environment the C. botulinum spores could germinate and then start producing toxin. But, if you are cooking home sous vide where you are serving the food right after it has been cooked, this shouldn’t be a concern.

Update (7/7/2009): On re-reading this post, one thing which I struck me in the last paragraph is that people might get the wrong idea when I talked about the “danger zone”, which for normal foods is traditionally regarded as between 40 and 140 degrees Farenheit.  (Although some spoilage bacteria can multiple at temperatures as low as 29 degrees Farenheit; the fact that you shouldn’t keep food between 40 and 140 for more than a four hours cumulative doesn’t mean that you can store foods for long periods of time at 38 degrees!)  The danger zone is however much larger for vacuum-sealed bags where botulism spores might be a possibility; some strains of botulism can germinate and grow at temperatures as long as 3.3 degrees Centigrade.   I didn’t mention this originally because I’m not terribly interested in doing restaurant-style storage of foods cooked sous vide.  The bottom line is that if you want to store foods for long periods of time, still in the vacuum sealed bag which was used to cook the food sous vide, you need to be very, very, careful.   Doing this right requires blast chillers and very strictly controlled and monitored temperature controlled refridgerators.   It is not something I would at all recommend for most home cooks; you’re much better off opening up the bag as soon as you pull it from the water bath!

25 thoughts on “Sous Vide, Revisited

  1. Wow! I had never heard of this and now after reading a few articles via wikipedia and google, I’ll be sure to ask the next time I go to any 5 star places in Manhattan if they use this. one part industrial science, one part food science with a pinch of botulism for taste! Thanks for the heads-up!

  2. Most NYC restaurants don’t like killing their patrons; it’s bad for business and bad publicity. 🙂 So most of the high-end restaurants always had very strict safety protocols in place in terms of heating foods to high temperatures, quick chilling of the food after it’s been cooked, maximum temperatures and time for storage the sous vide “meals in a bag”, etc. The concerns raised by the New York City Health Department were largely resolved by a series of educational sessions so the health inspectors could understand that done properly, yes, it could really be safe, and there was a reason why restaurants in France, who had been doing this for decades, had been able to avoid killing off their customers. I just didn’t talk about this much because I’m much more interested in sous-vide-the-home-game; I’d have no concerns with walking into high-end Manhattan restaurant and eating something that had been cooked using sous vide.

    So what if I’m paying $50 for an man dish that is prepared like a reheat-and-serve TV dinner? If it tastes really good, and the ambiance and service is impeccable, that’s what’s really important. In terms of the use of industrial science, that’s probably better than some of the other alternatives about what happens behind the kitchen doors. If you haven’t read Kitchen Confidential by Anthony Bourdain, I’d recommend it. It will dispel many of the romantic myths that many folks have about the restaurant business.

  3. Hi Ted, I re-read my comment and realize that they did not come across as I had intended. I am looking forward to the experience of eating food that uses a technique that aims to maximize both flavor, texture and nutritional value! The botulism remark should have had a smiley! I’d expect 5 star folks to not kill me like a chef preparing fugu. And if anyone would be a good candidate to try sous-vide-the-home-game, i’d be a kenel-hacker-type person who loves tinkering with the fiddley-bits 😉 Here’s hoping I see “Ted’s Sous Vide roast beef with root vegtables HOWTO” with proper “OPEN FOOD” licensing!

  4. Well, check out my previous post for a description of how to cook Roast Beef using Sous Vide. One change that might be worth experimenting with is to try extending the time, which should hopefully make the roast beef even more tender — although if it goes too long it could become too mushy. I’d probably go for 8 hours, and then 12 hours and see how it turns out.

    The other change I would suggest (although I haven’t tried it myself yet; it’s on my todo list), is to start the process by running a blow torch over the meat before sealing it in the bag; this will kill off the surface bacteria, but more important, create lots of flavor chemicals via the Maillard reaction which will then have a chance to migrate into the meat and flavor the entire piece of meat during the cooking process. Then, at the end, after removing it from the plastic bag, I’d run the blow torch over the meat a second time, to crisp up the outside.

    Unfortunately, at the moment the only blowtorch I own had last been used to melt some asphalt repair compound, and some got on the outside of the torch — so I don’t trust it for use in food preparation, the last time I tried making this recipe last weekend. I need to go to Home Depot and get myself a new blow torch, just for cooking purposes. (Also very useful for making a creme brulee, for example. 🙂

  5. Instead of a blowtorch, why not sear the meat on a very hot cast iron pan? We don’t do sous vide cooking (yet), but that’s a technique we’ll use sometimes — searing a cut of meat first, then putting it in the oven to finish.

    Plus, it gives you a panful of fond that you can use for a sauce!

    Of course, it’s not as fun as a blowtorch, I’ll hand you that. 🙂

  6. What I did for the sauce this time around was that I used the juices that that was in the bag plus all of the juices that came out when I sliced the roast beef. I then added eight ounces of demiglace (reconstituted from a paste of instant demiglace that I bought in the supermarket), and then thickened it with some white roux. (2 tablespoons of butter heated until it foams, whisk in 2 tablespoon of flour, cook for three minutes.)

    What I did this last time was just 10-12 minutes in a convection oven set at 550 at the end. You’re right, using a hot cast iron pan would also work; a blowtorch is just a lot more fun!

  7. Since I’ve never eaten anything Sous Vide, what can you say, at least of the beef you mention, has been the difference in the taste, aroma, consistency, etc.? Does it taste like other ‘chef’-cooked beef you’ve had?

  8. Hmm…. It has a stronger, deeper beef flavor, although that’s partially due to the home dry aging in the refrigerator. The meat is definitely much more tender and juicier, and best of all, most of the meet is beautifully medium rare, with just a hint of medium just at the edges where the outside has been browned. Basically, it’s tender almost like like a fillet mignon, but with much more flavor.

  9. I use the technique, but keep the food at temperature for up to 18 hours. Because it can’t overcook, it makes little difference if it is cooked 3 hours or 18. I would like to thank Ted for providing the time / temp chart.

  10. wow – all these information are really helpful for me – as a hopefully soon – a beginner in the sous-vide sector. at the moment i’m only using a vacuum-machine of lava and now i’m learning more and more about this technique.

  11. I was just getting the bug to play with sous vide techniques and found the Ranco temp controller in my search for a solution. (I’m extra tempted because we also have an electric smoker that could be more fun this way!) Then I looked for reviews and found yours, and then realized I knew the reviewer. 🙂

  12. Hey Abbe, it’s been quite a while since our paths have crossed!

    Have fun with sous vide; I’d love to hear how your experiments with it turn out!!

  13. also – did you get the thermal well / stopper accessory or do you do something else to avoid directly immersing the probe in water?

  14. I didn’t get a thermal well; I just placed the sensor into the water and it worked for me. Looking at the Ranco manual, it doesn’t say anything about whether or not the sensor is safe to immerse or not, so maybe what I didn’t wasn’t such a hot idea. It looked sealed to me, so it didn’t occur to me that it was something to worry about. Getting a thermal well might be very good idea, though, especially since Ranco implied that it was necessary by making a product for that purpose!

  15. Nice post…thanks. I just bought a Ranco unit, and found the following on their website:

    “Neither the Ranco ETC or Johnson A419 probes are recommended for direct “submersion in any liquid. The manufacturer recommends use of a thermal or bulb well. The copper well offered by the manufacturer is not suitable in all applications, especially aquariums where it may be harmful to fish, corals and other sea life. Thus a tight fitting plastic tube is recommended for aquarium use (some hobbyist will simply coat the probe in silicone instead).
    I will be looking for Teflon (PFTE) tubing to shrink around the probe. Ranco suggests goung past the tip of the probe with it, then shrinking the end until very soft and clamping with flat needle nose pliers;

  16. I enjoyed very much reading this post. The sous vide-method really requires some special attention to hygienic aspects. It´s not only the vacuum-machine itself, but also the vacuum bags that make the difference. They need to be temperature-resistant up to more than 100 degrees Celsius and the material should have a very high stability. Those interested in this healthy way of cooking will find some more information here… <link removed, since this this seem a bit too much like URL spam; you can find the non-English web site from the poster’s e-mail address, though.>

  17. @Sandra,

    I’m not sure I believe your claim that the bags must be temperature-resistent to more than 100 degrees C, etc., etc. It might be true if you are doing restaurant-quality sous vide cooking, where the bags must be flash chilled and then stored in a very cold (-20 degrees C) freezer to prevent danger from botulism spores, and then reheated by dropping the bag into boiling water.

    The home-style sous vide which I am recommending and practicing does not involve long-term storage, but rather cooking at temperatures of around 60-70 degrees C, which is enough to stop and/or kill the botulism bacteria, but not enough to kill the botulism spores, which requires high temperature and pressure which the sous vide technique tries to avoid. As long as you open up the bag immediately after cooking, there shouldn’t be a problem with botulism, since the food will no longer be in an anaerobic environment. But that also means that the bag isn’t going to be subjected to a very wide range of temperatures, which is fine since most homes don’t have the flash chiller and a sufficiently cold freezer to be able to safely store unopened sous vide bags for long periods of time.

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