TFP 2011: Sous vide master class (part 2)


Sous vide fish should be cooked at several temperatures followed by stepwise cooling for the best texture

Bruno Goussault started the sous vide master class at The Flemish Primitives 2011 by arguing that precise temperature or right temperature cooking is a better term than low temperature cooking. It’s really about knowing at which temperature the desired change takes place (or even better: knowing which time-temperature combinations will yield the desired results – this is a topic I will come back to soon).

Recounting the early days of sous vide, Bruno Goussault explained how he was once asked about how to produce prepare tender meat from a though cut. He was aware of a science paper on a slow cooking technique from USA (anyone know which paper this was?). It utilized a water bath, but the water washed away the juices. To avoid this Bruno wrapped the meat in cling film. A roast beef cooked at 58 °C turned out tender with a nice pink color. Then a friend working with plastics suggested that he should look into polyethylene (PE) bags in combination with a sous vide machine (boil-in-bag had already been around for some time apparently). Interestingly Bruno mentioned that during a recent Bocuse d’Or competition in USA where Bruno trained the American team, they replaced the plastic with a “skin” made from shrimps. Maybe we will see more “edible” skins used in sous vide in the future?

VACUUMING
Bruno then went on to talk about the vacuuming process and how time/pressure profiles should be adjusted to respect the shape and properties of the product, in particular when working with fish. A challenge with vegetables is the enzymatic release of ethylene, causing the bags to inflate (resulting in a poor heat conduction). The advice for vegetables and potatoes: use maximuum vacuum. But if you use the same setting for poultry the bones will turn out black because you extract bone marrow through the bones. Thus the vacuum should be sufficient to extract air from the bones, but not so high that the marrow is extracted.


Vacuum packing turns out to be a great way to impregnate food with flavors. As an example Sang-Hoon Degeimbre prepared oysters impregnated with champagne, cooked for 5 min at 83 °C and served with kiwi extract and an oyster leaf, Mertensia maritimia (Thanks Arielle!).

COLOR
When working with vegetables it is always the chlorophyll which causes problems (not the red/orange carotenes or the red/blue/purple anthocyans). This is due to the loss of the central magnesium ion. The easiest way to prevent this is by raising the pH. This can be done with baking soda (sodium bicarbonate), but gives an awful taste according to Bruno (and personally I would add that bicarbonate easily gives a mushy texture as well). A more advanced way to preserve the bright green color would be to add some other alkalizing/buffering agent such as sodium triphosphate (aka as sodium polyphosphate) or sodium hexametaphosphate (if you’re really interested, check out the paper Effect of pH on chlorophyll degradation and colour loss in blanched green peas for instance). And while we’re discussing color:  a side effect of the vacuum packaging of vegetables is that the air cells collaps, thereby reducing the diffraction of light which results in a darker and more intense green color.


Sang-Hoon Degeimbre shows how vacuuming gives greens a darker green color

STEPWISE COOLING
In restaurants sous vide is often used in a cook-chill-reheat fashion. For such a setup Bruno argued that it is vital to cool the meat or fish stepwise to allow a readsorption of the exudated juices (which also dissolve/carry away spices and Maillard products on the surface). If plunged directly into ice water fat and gelatin can cause the juices to gel, thereby effectively preventing a readsorption of the liquid. By taking the temperature down in a more controlled way the water holding capacity of fish/meat is improved and a portion of the exudated juice will be readsorbed (together with the flavors from the surface). A suggested stepwise cooling protocol for fish could be as follows: 10 min at room temperature, 10 min in cold water followed by 2 h in ice water. And it’s even possible to elaborate further on this – Bruno mentioned that he had developed a 4 step SV procedure followed by a 3 step chilling for Joel Robuchon. To me this also suggests that meat which is inteded for immediate serving should also rest a couple of minutes in the presence of the exudated juices. Would be interesting to know more about which factors influence this readsorption actually (maybe an interesting topic of a masters/PhD project?).

FISH
When preparing fish it is recommended to allow the fish to soak in a 5% brine for 10 min (Bruno lived for 3 years in Stavanger in Norway, and learnt this from a Norwegian chef during his stay – unfortunately he could not remember his name). This increases the osmotic pressure in the cells and prevents albumin from escaping (think of baked salmon with lot’s of white albumin leaking out) according to Bruno. After brining the recommended cooking times for a fish filet is then 1-3 min at 83 °C for pasteurization followed by 5 min at 58 °C for finishing.


Water baths set at 58, 66 and 83 °C. For a restaurant with only three water baths these are the recommended compromise temperatures.

TEMPERATURE
The many recommended temperature settings for meats and fish can be a challenge in a restaurant setting with a limited number of water baths. Bruno’s simplified approach was therefore to have three water baths at the following temperatures:

  • 58 °C (and in any case below 62 °C): At 56 °C albumin is sill runny, at 58 °C it begins to whiten (and the overall color of meat is actually a result of seeing the red meat color through a white “fog” of albumin covering the muscle fibres. This temperature is recommended for fish and meat that is to be served red.
  • 66 °C (in any case below 68 °C): The water holding capacity of the muscle tissue is dramatically reduced when heated above 68 °C. A temperature of 66 °C is therefore appropriate to retain the juiciness of meat. This temperature is recommended for poultry and well done meat.
  • 83 °C (in any case below 85 °C): This temperature is suitable for vegetables as they need a temperature above 80 °C to be properly cooked, but at 85 °C pectin begins to hydrolyze so it’s important to stay below that temperature. This temperature is also suitable for a quick pasteurization of the surface of fish and meat.


Potatoes cooked for 3.5 h at 83 °C turn out really delicious.

HYDROLYSIS OF CONNECTIVE TISSUE
The hydrolysis of connective tissue was also briefly mentioned. For a though cut of meat such as shoulder or top blade 4 h at 100 °C are needed to break down the connective tissue. At 66 °C the same process takes 76 h, and further lowering the temperature to 56 °C will require a full 120 h for the similar break down of the connective tissue. But in return the low temperature gives a meat with a very nice color. Interestingly, Bruno mentioned that due to different aging practices a similar cut in the USA typically would only require 72h at 56 °C to reach the same tenderness! So the time/temperature combinations should only be used as rough guides.


Lamb cooked for 36h at 66 °C has a very nice texture!

Other tips & tricks:

  • Rabbit and game are difficult to cook sous vide: sugar/glycogen in the muscles is converted into lactic acid which inhibits the cooking process (does anyone have more background information on this?)
  • The boling point of water at 10 mbar is 6.9 °C. This is the reason why everything you plan to vacuum pack at this temperature should be cooled to below 6 °C, otherwise the liquid will start to boil in the vacuum.
  • Regardless of what is cooked Bruno recommended a quick dip into a 83 °C water bath for pasteurization.
  • It is better to generate Maillard flavors before sous vide cooking: the flavors will dissolve in the exudated meat juices and then be readsorbed by applying a proper stepwise cooling. If desired a short browning can be applied after sous vide cooking for crisping of the surface.


A very engaged Bruno sharing his knowledge about sous vide cooking

At the end of the session I got to chat a little with Bruno. He said that he was very happy about the wide spread use of sous vide, but also emphasized that it is a technique that can amplify mistakes as well as successes. -Many chefs don’t respect the temperature recommendations! I visited a chef who cooked meat at 54 °C and it smelled terrible, Bruno told me. The different bacterias can greatly influence the flavor of the resulting product if care is not taken to eliminate them. I asked Bruno about low temperature/long time combinations, but he said that chefs generally are not patient enough. They already complain that they don’t have time for the long sous vide preparations. Bruno does a lot of sous vide consulting for chefs and restaurants (in France/Europe through CREA founded by him in 1991 and in the US as a consultant for Cuisine solutions), but does not have big hopes for sous vide in home cooking: - No, it’s a gadget! Sous vide works best for cook & chill in a restaurant setting.


Thomas Bühner explaining how his “raw” meat jus is prepared. In the background the minced meat is being prepared.

(RAW) MEAT JUS
In the last part of the master class the German chef Thomas Bühner (La Vie, Osnabrück) demonstrated the preparation of meat jus (i.e. the natural juice given of by meat when heated). Ground meat was vacuumed and cooked for 2.5 h at 56 °C. The meat juice was then collected using a chinois and further concentrated using a rotary evaporator operated at 120 mbar and a water bath temperature of 40-50 °C (important to keep the water below the temperature of the sous vide water bath in order to retain the raw meat flavor). Compared to a conventional cleared stock the reddish meat jus is opaque. The meat jus is devoid of Maillard flavors due to the low temperature used, and this ensures a raw and bloody taste. The taste was interesting I would say, but perhaps not very delicious on it’s own … But I’m curious how it’s actually incorporated in his restaurant.


Conventional stock (left) and evaporated meat jus (right)

Thomas Bühner also demonstrated vacuum infusion using the Gastrovac. Potatoes were pierced/scorched, submerged in the truffle jus and then placed in the vacuum of the gastrovac. Thomas then repeatedly let air into the Gastrovac to allow cells to collapse and improve the impregnation.

Tags: , , , , , , , , , , , ,
Filed under: equipment, interview, molecular gastronomy, science, sous vide

Comments

  1. Hugh Hancock Says:

    EXTREMELY interesting – thanks. The tip about pasturisation, correct breakdown times for connective tissues, and the trick with brining fish especially.

    You mention the lamb’s been cooked for 36 hours after saying the same temp would require 76 hours to break down the connective tissue – I take it that was a different cut, then?

  2. summer Says:

    Mmm looks delicious!

  3. Martin Lersch Says:

    Yes – the 76 h referred to brisket or shoulder. And in any case you will have to experiment as aging practices vary from country to country (and also between producers).

  4. sygyzy Says:

    Wow, I can’t believe how informative and practical this information is. This is exactly the type of post I have been waiting for. Just simple to the point advice. I am curious about the cook, cool, reheat advice though. I thought it was vital, from a safety perspective, to cool proteins you hope to eat later as fast as possible. The room temperature plus water idea is dangerous, no?

  5. Espen Says:

    Great post, I’ve just started to explore the wonders of sous vide myself with a sous vide supreme. Even though it is a “simple” way of doing there are some many aspects of it that will take a lot of time to perfect for a simple home cook as myself.

    I see that this post is called masterclass part 2, where can I find part 1?

  6. Martin Lersch Says:

    Espen: It’s only this one post about the master class, but it’s the second of my posts about The Flemish Primitives 2011. The first one you can find here.

    sygyzy: Consider that after cooking the whole pack is pasteurized. I wouldn’t be concerned about an hour at room temperature or in cold water.

  7. Renn Says:

    Martin,

    Do you know if TFP will make DVD/online availability of any of the sessions (particularly this one). Reading your wonderful report only makes me hungry to get more in depth…

  8. Martin Lersch Says:

    Renn: AFAIK the session was not filmed. I’m not sure about the rest of TFP though.

  9. Bernard Lahousse Says:

    This edition will also be available on IPad. It will be a magazine with recipes and movies. Everything on the Monday and some info on the masterclasses. I will keep Martin updated. In the meantime ‘the essentials’ of jean Pierre Gabriel contains a lot of valuable info concerning this topic (book in cooperation with unilever)

  10. vassilis Says:

    Very nice report
    do you have more about the gastrovac? like temperature / time / vide?

  11. Thomas Says:

    In the “tips & tricks” section of your report it is mentioned “that rabbit and game are difficult to cook sous vide” and you asked whether anyone has more background on this. Unfortunately I have no explanation for this, but noticed, that low temperature cooking of game (not only sous vide) in fact may result in extreme soft and tender results comparable to liver, but not always! I have read similar findings in blogs (with explanations linked to glycogen/sugar as well), but nothing really convincing. So, just repeating your question, has anybody more insights?

  12. Barzelay Says:

    I thought that the mushy potential of cooking vegetables with baking soda was due to alkalinity, and that any other basic additives would therefore have the same effect. You seem to imply otherwise. Is there something about baking soda besides its pH that causes the mushy effect?

  13. Martin Lersch Says:

    Bernard: Sounds great!

    vassilis: Sorry – no.

    Barzelay: Addition of a base will increase pH, but if it’s the conjugated base of a weak acid it will rather stabilize pH because we get a buffer system. This allows a more careful control of the final pH. I don’t know if you’re familiar with buffers and how they work? Theoretically adding a very precise amount of baking soda should yield the same effect as any other base. What could complicate matters is that some anions may form metal complex and act as sequestering agents, although I don’t think this is the case here.

  14. Barzelay Says:

    I just read a bit about buffer solutions. So that’s why, in the paper on color preservation of green peas, the basic solution they added also had citric acid in it? I thought that seemed strange until now.

    So, getting back to the question of what makes the veg mushy, is there any reason to think that the effect would be greater with baking soda added than with other basic solutions?

    I also wonder whether the mushy effect would negatively impact the texture of even a puree of the blanched veg. If the alkalinity is somehow destroying the cellulose or pectin, then I wonder whether it might not matter if dealing with, e.g., a pea puree?

  15. Orges Says:

    Hi Martin,

    Very interesting, but there are some misconceptions and/or mistakes, some of them very important:

    - Temperature controlled chilling might be dangerous. Despite the potential effects on quality, the product should be a time as short as possible at high and medium temperatures, since minimizing microbial growth must be the priority. Be careful!!

    - 56ºC for 120h sound somehow dangerous. We have been doing research (still not published) about microbial growth at different sous-vide cooking temperatures, and 56ºC is about to be problematic for some pathogenic bacteria.

    - The tenderness due to proteolysis previous to cooking (conditioning) and that achieved by cooking at moderate temperatures are totally different (and from my point of view, not complementary). The former is due to hydrolysis of myofibrillar and sarcoplasmic proteins due to proteolytic enzymes. The latter is due to collagen solubilization and gelatin formation.

    - I am advising a PhD student who is studying sous-vide cooked lamb. 66ºC-36h sounds “dry”, at least for Spanish lambs, which are slaughtered either at 6-7 (suckling) or at 23-25 kg.

    - The expression “sugar/glycogen in the muscles is converted into lactic acid which inhibits the cooking process” has no meaning for me. What does mean “inhibit” here? And how is the glycogen converted in lactic acid at sous-vide cooked temperatures? AS far as I remember, all enzymes involved in the anaerobic oxidation of glucose are denatured below cooking temperatures. Lactic acid is formed exclusively by enzymatic processes which take place when the muscle is still not heated.

    - “Regardless of what is cooked Bruno recommended a quick dip into a 83 °C water bath for pasteurization.” I completely agree with this, but this is useful only for surface bacterial population.

    - “It is better to generate Maillard flavors before sous vide cooking: the flavors will dissolve in the exudated meat juices and then be readsorbed by applying a proper stepwise cooling. If desired a short browning can be applied after sous vide cooking for crisping of the surface” We are working on that, comparing the volatile compounds profile in different heating procedures.

    Cheers

  16. fooducation Says:

    A great post, Martin, and also some very useful comments. I found the statement “- No, it’s a gadget! Sous vide works best for cook & chill in a restaurant setting” interesting. Look forward to see how this develops in the forthcoming years.

  17. Barzelay Says:

    I was also puzzled by the statements that rabbit and game are difficult to cook sous vide. I have cooked rabbit, pigeon, guineafowl, wild venison, wild boar sous vide with great results. I have never experienced any unexpected effects or off flavors as compared to domesticated animals.

    Rabbit in particular is difficult to cook sous vide in terms of process because it cannot be cooked and chilled and then re-heated without suffering from a crumbly texture. I assume this is due to an enzymatic process. It is only the case with the lean parts of the rabbit (loins and tenderloins), not with the legs or flap meat. So, it simply must be cooked a la minute rather than cook, chill, reheat. When cooking the full saddle (loins and tenderloins wrapped in the flap, and wanting to heat and chill in order to “set” the roulade, I have in the past made the roulade (preferably with Activa then let it set) then cooked it briefly at a high temperature (83C would be fine) for just long enough to cook the outside but not long enough to cook the tender bits inside, then plunged immediately into ice water and cooled rapidly before the loins can warm. Then hold in the refrigerator for a la minute cooking on the same day or the next day. I got this technique from Under Pressure.

  18. Martin Lersch Says:

    Jorge: Thank you very much for your thorough comment.

    - If the whole piece of meat has been cooke sufficiently long to be pasteurized – would it still be dangerous with a temperature controlled chilling procedure? I would think no, but I may be wrong?
    - I will be looking forward to see the paper about 56 °C cooking (as well as results from your PhD student studying lamb and the one on the effect of heating regimes on volatile profiles)
    - Thanks for clearing up the difference between enzymatic proteolysis and collagen solubilization – I’ll try to incorporate this into the text. Once you say it it’s obvious, but I realize that I have been using inaccurate terms here, so thanks!

    All: Regarding the lactic acid and rabbit – I wish Bruno had explained more about this. The only thing I got down on paper was what I wrote, but I realize now too late that I should have inquried more about this.

    Barzelay: Hats off for your experience with exotic meats. I’d have a hard time getting hold of such meat where I live now… It’s interesting though that you mention the crumbly texture – maybe that’s what Bruno was referring to?

  19. Gourmetologist Says:

    Hi,
    what a nice post, I’m getting crazy about Sous-vide and every tips is welcome!

    Just one point, you already mentioned briefly: The age of the animal/meat.
    There is a huge different in meat depending of this. I have experience in Spanish and Finnish meat, they slaughter animals at very different age thus, the “meat quality” is very different. More aging meat has more connective tissues.
    And, of course, the time-temperature for that meat should be different to tenderize it.

    May I suggest a post with the slaughter age of animals in Europe and America? :)

  20. Gourmetologist Says:

    I forgot to add tio mny last comment:
    Never re-heat sous-vide food in microwave. The reheating is not homogenous, so some areas will be still chill and others over-cooked.
    I suggest sous-vide bath at 45-50 degrees for 15-30 min depending of pieces thickness.

    Cheers

  21. Orges Says:

    Martin,

    .- Pasteurized means a temperature enough to kill most vegetative forms of pathogenic bacteria. This not includes spores of Clostridium (botullinum or perfringens) or Bacillus cereus, which are very dangerous and are not destroyed with pasteurization. For these pathogens, if the food is not sterilized, there must necessarily exists another hurdle during storage. In this case, the most effective and easy one is refrigeration (below 2ºC would be better). And all the time the food is kept above this temperature, is time for these bacteria to grow and produce toxins, especially at temperatures between 20-40ºC. Moreover, the thermal treatment produces a decimal reduction of microorganism. That means that if the initial amount of a given microorganism in the food is 10000000, and the temperature treatment produces a 5 time decimal reduction of this microorganism, the final number would be around 100 (consider that if all microorganisms were killed, the shelf life would be years, like in sterile products). Again, temperature must be as low as possible as soon as possible, in order to control the growth of remaining microbes.
    .- I will keep you inform about the papers about vacuum cooking. There are some curious results and some other predictable (although not scientifically shown up until now).

    Goumetologist, for a restaurant, I would suggest a slightly higher temperature, but lower than that used during cooking. 45ºC is not enough for handling and serving. I would say around 60ºC would be more adequate. And the muscle of older animals has not a higher amount of connective tissue, but a tougher and less soluble collagen due to very stable inter- and intra- molecular bonds formed during animal life. In order to achieve gelatin formation for this type of collagen, a longer time and/or a longer temperature is needed. Perhaps, in some cases, sous-vide should not be the chosen option, because it will never be enough to tenderize those meats with a high amount of insoluble and thermally stable collagen.

    Cheers

  22. fooducation Says:

    Since there has been so much focus on microorganisms in food in the discussions, I might add a literature tip. For Scandinavian readers, Bøgh-Sørensen & Zeuthen’s Konserveringsteknik 1 & 2 might be a good reference. Not very recent, but 2002 and 2004 respectively should be ample for the more established questions on pathogenics. Book no. 1 has its focus on contemporary methods whereas no. 2 concerns traditional methods for preserving foods (cured meats etc)

  23. Arielle Says:

    The leaf in your second picture looks like an oyster leaf – Mertensia maritimia- which has been showing up paired with oysters lately (as it has a taste somewhat reminiscent of oysters)