Today’s Secret Ingredient…. Heat

I wish with everything in my little cooks heart that Harold McGee wrote for the NY Times every Wednesday.

This week we are treated to an introduction to an ingredient every cook uses every day with very little understanding. In this weeks article, he talks about heat.

Having been in the kitchens I have been in,  I have been exposed a bit to the thought of better using heat to cook foods.  Take sous vide, a word that we hear thrown around with trendy modern food is actually an exercise in the most efficient manner to apply heat to food.  Yes, the method of putting food in vacuum sealed bags and cooking it in water has been used for a few decades now.  However it’s the more recent study into how the energy of heat changes and effects the molecules in our food that resurrected this method from the depths of reheating catered dinners, introduced perfectly controlled thermobaths from laboratories, and brought it to the forefront of haute cuisine.

While much of the study of heats effects on food relate to meat cookery, where our use of the energy is at it’s most inefficient, the application I found most interesting was for potatoes.

Almost every restaurant has mashed potatoes on their menu.  It seems to be a game of chasing the white rabbit, that of making the perfect, fluffiest, creamiest, mashed potatoes.  We as cooks hear legend of different kitchens and their ethereal potatoes, like Joel Robechons, “passed through the tammis 5 times!  Mounted with twice their weight in butter!”  Every kitchen has their spin on making theirs better.

At WD-50 I saw something done to the potatoes that makes a cook scream, “yes!” A method of cooking the potatoes with an explanation using true understanding of the molecules inside the potatoes and the effects of heat on them.

The potatoes are peeled, sliced, and cooked in a water bath at 65 degrees celsius for 30 minutes.  The potatoes are transferred to an ice bath to cool completely.  At this point the potatoes are still crisp, seemingly unchanged.  Once cooled, the potatoes are cooked just as you would have had you just peeled them.  If the potatoes are seemingly unchanged, you might ask what on earth did they just do?

Well, working with a method used by the commercial mashed-potatoes-in-a-box companies, they use just enough heat to cause the starch granules inside the potatoes to swell.  Think of these granules as little sacks of starch molecules.  They absorb water, and the starches inside grow.  If they are mishandled, or bounced around by too much energy, say that of boiling water, these little bags break open freeing all those starch molecules.  These rouge starches are now free to retrograde, recrystallize and cross-link forming long gummy chains.  This is not good.

So, after cooking the potatoes in gentle heat, just long enough to make these starch bags swell, the potatoes are then cooled in an ice bath.  The starch in the potatoes are allowed to recrystallize, or retrograde.

Wait, didn’t we just say that was bad?  Well, it’s bad when the starches aren’t contained.  Because of the gentle application of moderate heat those little starch sacks are intact with swollen starches inside.  The ice bath forces these starches to retrograde, gel, set, what every you may, inside their sack.  Retrograde is permanent.  The starches are now cemented into place safely inside their granules, and you can now cook the potatoes with a more aggressive heat, and break apart the starch sacks by mashing and passing through a tammis, processing the potato.  You can manipulate these particles into a nice smooth, even mashed potato with out risk of releasing the starches from their containment.  No gummy paste, no stringy gluey mashed potatoes.

And the best part?  You can cool the mashed potatoes, and reheat them for service with no change in texture.

Pretty cool, huh?

12 Responses to “Today’s Secret Ingredient…. Heat”

  1. Harlan says:

    Ooh, interesting. I suppose you could do a similar thing with potatoes, wrapped in foil, in a pot of water in a 65 C (150 F) oven. Except that my oven only goes as low as 175 F, I think… :(

  2. Hungry says:

    You don’t necessarily have to use the oven – get a pot of water, stick a thermometer in it, have some ice cubes ready, and just monitor the temp so that it remains 65 c.

  3. kris says:

    Really cool… especially the ability to reheat. Is this the same concept behind the “hot stock” risotto method only on the other end of the spectrum (i.e.-looking to break up the starch granules and release the molecules)?

  4. dana says:

    Harlan- You would want to do it stove top, just as Hungry recomends, and there is no need to wrap them in foil.

    Kris- To my knowledge I don’t think you want to break the starch granules in rice either. Infact, the chef I work for is militant about our risotto being shaken, not stirred for this exact reason, and I have always been told not to use a metal spoon lest you break up the starch. I believe you are trying to release the granules, but avoid breaking them and releasing the free starches inside. Those free starches will form chains which give an improperly cooked risotto that gloppy thick feel versus the light creamy feel of a properly “shaken” risotto.

  5. Rogue says:

    What are rouge starches? Are they pink, and used to give color to cheeks?

  6. SP says:

    You can also buy a heat diffuser which allows you to heat things at very low temperatures on the burner, so that you dont have to basically stand in front of the stove for the entire 30 minutes staring at the thermometer.

  7. one food guy says:

    The science of food is fascinating. I’ve enjoyed watching some of the competitors on Iron Chef America bring their chemistry sets to Kitchen Stadium, Chef Dufresne included. Very cool stuff.

  8. James Naquin says:

    This technique was mentioned in Jeffrey Steingarten’s “The Man Who Ate Everything”. I believe it says that he learned the technique from Shirley Courrier. It is discussed in her book “Cookwise”. Her book is really informative and a little less technical than Harold McGee’s.
    This is my first visit to your site, and i will definitely be back! Fun stuff…

  9. Kendall Collingridge says:

    wow, I can’t wait to try this on my gnocchi… Thank you so much!!!

  10. gresham says:

    just wanted to know…. do you start the cooking process at 65*c or with cold water? im kinda new to this, so please help

  11. Andrew says:


    I would get the water bath to 65c before I put the potatoes in. I do have two other questions:

    1) I assume the potatoes are put directly into the water and are not vacuum sealed first. Am I right?

    2) Why 30 minutes? Is the time important? Can they spend too long at 65c? If the time is important wouldn’t the size of the slice be just as important?

    If anyone is interested in trying this sort of stuff at home, I have found a fairly cheap and accurate controller that lets you keep a crock pot at a constant temperature. It’s not as perfect as a restaurant, but I’ve had good results.

  12. Evelin says:

    Thanks, that was some great information! I’ve also learned that to have boiled potatoes that don’t easily break, it’s best to first boil them for 30 minutes below 70C and then raise the temperature. Haven’t yet tried it, but at least it makes me feel good to know I could do it:D

Leave a Reply