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.

The TGRWT #15 challenge was to pair smoked salmon with dark chocolate. I decided to encase a piece of hot-smoked salmon in a cocoa gel and serve it with sugared slices of lime. But as you can see from the pictures quite a lot went wrong… But it tasted quite nice!

Smoked salmon encased in agar cocoa gel
Agar gel:
400 g water
10 g cocoa
35 g sugar
2.5 g beef stock powder
10 g balsamico vinegar
35 g lime juice
1.8 g agar (0.37%)

smoked salmon
lime
sugar

Combine all ingredients for the gel and bring to boil. In a suitable (shallow) tray, pour one layer and leave to gel. Place salmon on top and pour more of the hot agar solution. Leave to gel and repeat until salmon is complete covered. When gelled, invert and slice carefully. Serve with thin slices of lime sprinkled with sugar.

Verdict: Even though I didn’t have time to finish the dish presentation-wise, I did of course taste the different components together. The lime added much needed freshness to the cocoa gel and combined well with the fish. The cocoa was not overpowering. The dish will work fine for a starter or as finger-food once I get the presentation right.

Lessons learnt

• For layered agar gel preparations it’s crucial that the next layer is poured while piping hot so that it can melt a little into the layer below. Because of agar’s significant hysteresis the gelled agar must be brought up to around 80-90 °C to melt.
• The box I used was way too deep (and the best at hand at the moment), but it might have worked if I had lined it with plastic wrapper. The layers came apart as I was trying to get it all out of the box. A higher agar concentration would make for a stronger gel, but it would also trap more flavor. Possibly it would also be more difficult to get the layers stick together at higher agar concentrations. Does anyone have experience with layers agar preparations?
• The hot-smoked salmon tastes very nice, but it’s texture was a litte to tough. I tried making slices, but both the salmon and the cocoa gel fell apart. This could be solved by switching to cold-smoked salmon. But a potential problem here might be that it will become “cooked” (and change color from translucent to opaque) once the hot agar solution is added. In that case one might have to revert to gelatin which melts at lower temperature.

You can also do it the other way around. Let’s say you have boiling water and you know that your tap water is approximately 10 °C. If you want water at approximately 37 °C, you can do as follows:

Start by writing what you have to the left (100 °C and 10 °C) and what you want in the middle (37 °C). Subtract: (100-37) = 63 and (37-10) = 27. And voilá – you need 27 parts water at 100 °C and 63 parts at 10 °C (and 27:63 simplifies to 3:7 which is what we found above). Now of course if you really wanted water at 37 °C, you would simply put your finger in to see if it’s at body temperature…

Are there any practical applications of this? Yes – a simple, but elegant way to prepare fish would be to drop a fish of known weight and temperature (fridge @ 4 °C or freezer @ -18 °C) into water that has been brought to boil. Cover pot and turn off heat. The amount of water would be calculated based on the desired temperature of the fish. We are assuming here that there is no heat loss to the surroundings, which of course isn’t quite true. How fast pot of water will cool depends on how much water you use and on the pot. This can be corrected for, and luckily someone has already done it. More on this in my post on how to cook fish in cooling water.

We can apply the temperature calculation from above to figure out roughly what the temperature will with this cooking method. 800 g of fish from the fridge (4 °C) and 2,4 L of boiling water gives a temperature of (0,8 x 4 °C + 2,4 x 100 °C) / 3,2 = 76 °C. The cooling curves for a pot with 2,5 L of water suggest a temperature loss of 15-20 °C in 30 min which would bring us down to 55-60 °C which – considering that no thermometer is used – is quite good.

A slightly different approach for cooking fish was presented by Haqvin Gyllensköld in the Swedish book “Koka, steka, blanda” from 1977, which I became aware of through Östen Dahlgren’s book “Laga mat – hur man gör och varför”. In stead of keeping the fish at a constant temperature (which requires quite some attention unless you have a thermostated waterbath), in this method, as the hot water cools, the temperature of the fish increases until they’re at the same temperature.

This is how you do it:

1. Weigh the fish
2. Boil the triple amount of water
3. Add some salt to the water (15 g / L)
4. Put the fish in the water and remove the pot from the stove
5. Check the graph below for how long the fish should be left in the cooling water
6. Serve!

Need help on fish names in different languages? Yeah, me too!