vegetable sous-vide

We constantly focus on temperatures for the breakdown of proteins and collagen when we utilize the sous-vide method for cooking meats.  Some of these temps have become chiselled into our brains after so many trials that an educated guess has become an experienced guess...  Still, there is no substitute for cold scientific knowledge.  This bit of information came along with an epiphanal mental 'hallelujah' chorus singing in the background.  The information was delivered in the broken English of Bruno Goussault with Bruno Bertin in the DVD series of workshops from the 2007 Star Chefs Congress.  (This disc set is an incredible investment... even if you were in attendance and you are the king of note-taking, there is always missed information that comes to you later.)

The epiphany was Goussault's recitation of the cooking temperatures associated with vegetable matter, not animal matter.  True, I have cooked vegetables in the bag before but it was like shooting mice in the dark without having a knowledge of breakdown temperatures.

Chef Bertin was cooking polenta in a vacuum sealed bag in a CVap.  Goussault explained that all vegetable and fruit product should be cooked at a temperature of 83C.  Why this temperature?  Let's look at the components of plant matter.  There is obviously sugar present depending on the ripeness and the plant itself and there is also cellulose matter which does not breakdown at normal cooking temperatures.  The other 2 components that must be respected in relation to texture are starch and natural pectin.  Starch will begin to breakdown at temperatures of 78C or 80C and above.  Natural pectins, which are the molecular glue holding all plant cells together, do not begin to break down until 85C.  This knowledge along with a controlled method of cooking allows some great new textures to be achieved.

The polenta recipe used was interesting, but I wanted to give it a run on a smoked potato component in a dinner we had scheduled last night.  I tossed the potato in olive oil, salt, and pepper and let them smoke for awhile.  Once the smoke flavor was fixed on the surface of the cubes (along with the oil which will act as a vehicle to bring the smoke flavor through and through), the potato was bagged up and thrown into an 83C water bath for 2 hours (the top most picture is of the potatoes out of the bag after cooking).

The result was a potato texture I have never experienced before.  The completely broken down starches yielded a creamy texture while the potato still had a slightly crisp bite from the intact pectins.  Obviously, the texture was uniform throughout the cubes.

The next question (and one that I will discover today) is... will this texture remain if cooking is prolonged another couple of hours or indefinitely.  I plan to play around with soft grits cooked in the bag, and I'm going to drop some more potatoes in the water bath as well... they both cook at 83C.  Chef K suggested that this could be a great cooking method for yucca as well (the extremely high starchiness of yucca has always turned me off to it, so it will be exciting to examine it's controlled cooked texture).

Comments

[Ouroboros]

What variety (or description) of potato did you use?

[uwe]

Grits? You ole C-A. Will you do some okra for me and see how it affects its viscosity vs. crunch? My south and east side can't wait to hear the results of grits, but my central and west side is psyched about the yuca.

[chadzilla]

The potato was Yukon gold.

Uwe. Don't get too excited about the grits or the yuca... they were the low points of the following trial. I didn't use no instant grits neither, cher!

[chris]

Chad,
Sous vide veg yeilds great texture but usually the color is compromised. I like the idea of the sous vide pots, maybe smoke some ice cubes and cook them in the melted liquid. You definately have to think about what veg works with sous vide in terms of preserving color. Cardoons, artichoke, beets, veg where there color is dul or the color really comes through no matter what technique you are using. Squash is coming in and I wonder the benefit of preserving the texture of squash, if you over cook it it is mush. I'll have to test that one.