November 13, 2013
Pressurized Cooking

Some of the techniques used in vacuum cooking lead to watermelons looking like Bluefin tuna or sliced apples appearing translucent. This cooking process was developed by the Chief Scientist of CREA (Culinary Research & Education Academy), Bruno Goussault, a passionate and inexhaustible biochemist. He built the company in 1991 with the support of Joel Robuchon and Henri Gault.

Yam | How difficult is it to use vacuum cooking for vegetables and fruit?

Bruno Goussault | They require a specific setting on the vacuum machine: there needs to be a strong suction to remove as much air and gas as possible from the product. Due to the specific texture of fruits and vegetables: roots, tubers, stems and leaves, not only is it important to extract the air between the leaves, but also any gas in the parenchyma of roots and leaves. Vegetables breathe through pores under their leaves, with ethylene filled cavities, a ripening gas.  Fish, for example, have delicate flesh, so they require less suction.

Yam | What will happen if suction is not strong enough?

B. G. | While cooking, a layer of air or gas will appear between the vegetable and the plastic bag. The vegetable will float in the circulator’s water and will not cook evenly. 

Yam | What did you find out while cooking fruit and vegetables under vacuum?

B. G. | Vacuum sealed cooking amounts to sucking the air out of food, and welding the bag so it is sealed. In the process, the air floats back into the bell of the vacuum machine. The packaged ingredients then receive atmospheric pressure: their textures are compressed; they receive the equivalent of “a slap”. This pressurized effect offers loads of possibilities. 

Yam | Tell us about your first experience with pressurized cooking.

B. G. | It was with Thomas Keller, an American multi-starred chef . We were testing watermelons: with this pressurized phenomenon, the fruit had become dark red, appearing like blue fin tuna.

Yam | Had the color of the watermelon changed?

B. G. | No, only our perception of the color had changed. The light passed through without being diffracted by small pockets of gas in the parenchyma. To make things simpler, the light did not go through the fruit in the same way.

Yam | What are the culinary applications of such a discovery?

B. G. | First of all, our interest is to surprise the guest. Several leaders diverted perceptions. Andoni Luiz Aduriz in the Basque Country had the idea of a watermelon carpaccio looking exactly like a carpaccio of beef. Michel Richard prepared a half-watermelon half-tuna tartar.

Yam | What other vegetables are suitable for pressurized cooking?

B. G. | The results are excellent with spinach. After undergoing atmospheric pressure, the leaves turn an intense dark green. They also have the advantage of not wasting water while cooking; making them soft and juicy.

Yam | This being said, we can imagine that this technique works with other greens?

B. G. | Yes, it was tested on basil leaves; we obtained an extraordinary color of pesto. It also worked with Chinese cabbage leaves, mint, watercress and lamb's lettuce. However, tests have been catastrophic with broccoli as its structure is too firm and cannot be "crushed". 

Yam | Pressurized cooking helps keep the green color of chlorophyll?

B. G. | The chlorophyll contains a magnesium atom that is not stable when cooking. This is why vegetables become khaki if cooked too long. In classic cuisine, the chefs quickly blanch them before cooling them in ice water to block the green color. This pressurized technique reinforces the green of chlorophyll, making it more intense and most likely a little more stable.

Yam | And with fruits?

B. G. | We did tests on slices of apples and mandolin cut pears. The result is remarkable: they become translucent. You can also play with this transparency with slices of fennel, radish and turnip. This is only the beginning!