sous vide tempered chocolate
I’m not much of a chocolatier, but I’ve watched my dad temper chocolate and make truffles a dozen times or so.  The transformation that takes place during the tempering process is fascinating, and it only becomes more curious with my first attempt to temper using sous vide.  Notice the pattern of dark, shiny dots and lines?  I didn’t put it there.

The process of tempering chocolate is all about forming the cocoa butter into a regular crystalline structure.  This gives properly tempered chocolate its signature glossiness and brittle snap.  I found these instructions on the tempering process and adapted them for sous vide. Here are the steps I took:

  1. I crushed 5.00oz of Scharffen Berger Unsweetened 99% Cacao Baking Chocolate and sealed it in a 12” square vacuum bag.  The sealed chocolate was spread out in an even layer, about 1/4” thick.  [BTW, unsweetened (even the good stuff) chocolate tastes like shit.  I chose it because it was in the pantry.]
  2. I set my Sous Vide Professional (generously on loan from Polyscience) to 115F in a 4-gallon basin with about one gallon of water.
  3. I added the bagged chocolate and it began to melt instantly.  I felt the bag for lumps, and within 3 minutes, all of the chocolate was melted and presumably at exactly 115F. 
  4. I lowered the set temperature on the sous vide machine to 84F and added a few large ice cubes and short bursts of cold water until the temperature reached 84F.  This process took about 7 minutes.  I held the temperature at 84F for 2 minutes.
  5. Finally, I raised the set temperature to 88F.  The bath took 1-2 minutes to heat to 88F and overshot the desired temperature by .5F (for a moment, the temperature of the water bath was 88.5F).  I held the chocolate at 88F for 2 minutes.
[I learned later, after reading this article, that it may not have been necessary to raise-lower-raise the temperature, and that bringing the chocolate directly to 85-87F should have done the trick.]

I removed the bag and wiped it dry.  Then, I cut off one of the corners leaving a small opening, perhaps 1/16th of an inch, so I could pipe out the liquid chocolate.  I had a few Trader Joe’s Candy Cane Jo Jos (fake mint Oreos) lying around, so I covered them with the chocolate.  While it was still molten, the chocolate looked great (see below).

I the chocolate cool for 30 minutes before getting impatient and popping my tray of cookies into the freezer.  I let them freeze for about 10 minutes before removing them to take pictures (the surface temperate of the chocolate was 56F when I removed the cookies from the freezer).  Strangely, during the cooling process, a bizarre pattern formed on the surface of the chocolate.  It didn’t look properly tempered, as most of the chocolate was relatively dull and didn’t have much snap.  However, the chocolate was covered with an intricate pattern of darker, shinier dots and lines that reminded me of Damascus steel. 

Without knowing much about the molecular process of tempering (besides the very helpful information found here), my guess is that the dark areas represent places in the chocolate where beta crystals began to form.  The lighter, duller areas may be places where, for whatever, reason, the crystallization never quite took off. 

In every other method I’ve seen for tempering chocolate, the chocolate is stirred or circulated.  I couldn’t tell if the motion of the chocolate was purely to promote an even temperature, or if was critical for forming the crystalline structure of properly-tempered chocolate.  Since I was using a precisely temperature-controlled bath to heat my chocolate, I didn’t have to worry about circulating it to even out the temperature.  However, perhaps circulation really is key to an even temper. 

If there are any tempering experts out there, I’d love to hear your thoughts on this mysterious pattern!