The Shiny Science of Chocolate / by Anne

chocolate.trufflesIt’s shiny, it’s snappy, and it’s taken for granted.  How many times in my life have I sunk my teeth into a glossy bar of chocolate without appreciating the science and care involved in keeping this chocolate from melting in my hand?   (To answer my own rhetorical question with basic math, it had to be at least once a month, since puberty, until about a year ago, making it 300 times, bare minimum.)  A bowl full of shiny chocolate bars that have been melted down and then left to cool naturally will result in chocolate that crumbles when broken and has a dull, matte finish.  It melts more easily than its original form, too.   Why does this change happen?   Well, I'm warning you, the answer involves molecules. When I was learning about how to dip chocolate truffles in tempered chocolate last year, I wanted to know more about the mysterious and specific instructions about tempering.  Why do you need to go out and buy a chocolate thermometer?  Why do you heat and cool the chocolate more than once?  Why shouldn't I just heat 'er up and start dipping?  The beautiful science behind tempering helped me to understand and appreciate the method to the melting.   

If you are short on time, just skip down to an exquisite chocolate truffle recipe with fresh mint (mint optional).  The truffles are dipped in shiny tempered chocolate and cause a show-stopping hubbub in the room.  If you have a few moments, though, read on to celebrate yet another reason why chocolate is so amazing.

You might already know that sweet chocolate is made of cocoa solids and sugar suspended in the lovely, melty cocoa butter.  However, in spite of this melty quality, cocoa butter, like diamonds or graphite, is a crystalline substance.  In fact, cocoa butter can have more than one form of crystal in its structure.  In cocoa butter there are actually six different kinds of crystals, labeled Types I through VI, each with increasing stability and melting points. 

One of the six types—Type V—is considered optimal for making candy bars or couverture.  Besides having a higher melting point (second only to type VI), Type V has a more stable structure than the first four, resulting in the glossy sheen and a pleasing snap when you break it.  Type VI, while also possessing the desired attributes in even higher amounts, is not desirable.  Its high melting point causes a less pleasant mouthfeel—plus, it’s difficult and timely to form. Meanwhile, the four less stable crystals melt too easily, have a matte finish, and crumble when broken.  

Left to its own devices when cooling, chocolate will start to form a hodgepodge of all these crystal forms.  In other words, left to its own devices when cooling, chocolate will make a much less fun Easter Bunny.   The good news? Even if you have untempered chocolate to deal with, you can still bring it back to temper.

There are several ways to temper chocolate, and I've been using what is called the seed method.  You melt it until it reaches a temperature that is high enough to break all crystal bonds (but not too high, which will separate the cocoa butter from the solids).  Then you cool it slowly, further bringing the temperature down by stirring in some some chunks of still-tempered chocolate (such as pieces of a candy bar, but I’ve been using bulk chocolate).  The chocolate starts to generate crystals of varying types, but with the tempered chocolate nearby, many disordered molecules fall in line and start to form more type V crystals.  However, other crystals have had a chance to form in the meantime, even with an abundance of type V.  This is why you heat it back up again very slowly to melt the less stable, easily melt-able crystals, so that all you have left are (mostly) type V.  The newly free molecules naturally start to form into the adjacent type V crystals as long as it remains at this optimal temperature that keeps type V stable and melts the other ones. 

If the chocolate starts to harden on the sides as I'm dipping chocolate, I'm supposed to slightly heat it up again, but I've discovered that messing with it too much will allow too many lower types of crystals to form when it cools again, and this disorder will cause streaks and less stability in the chocolate. 

Here is an example of pretzels dipped in tempered chocolate compared to pretzels dipped in the same chocolate after I messed around with it.  Only a few minutes' (and degrees') difference makes a dramatic visual impact.

chocolate.pretzels.tempered.and.not

Besides the beautiful fact that chocolate is a crystalline substance, it’s also interesting to note that chocolate is an extremely dry medium.  A single drop of water in smooth, “wet”-seeming melted chocolate will result in a stiff, grainy, gritty mess.  The intense dryness immediately absorbs the moisture and the chocolate has the inclination to clump up around the water molecules.   So, when tempering the chocolate you not only have to keep your eye closely on the temperature of the chocolate—you also need to make sure that no water comes into contact with your chocolate, including condensed steam from a double boiler, if you use one.  If the chocolate does seize, you can still use the chocolate for other baking purposes, just not for dipping. 

So many details and so much attention for a little snap and shine.  Is it worth it?  Absolutely.  Once you take a bite of a truffle that you have dipped into tempered chocolate, you’ll see what I mean.   You pick up this beautiful treasure that you yourself crafted.  It glows in your hand (rather than melting in it).  When you test it with your teeth, you feel the pleasing snap, followed by a rich, softer center full of smooth and creamy chocolate ganache.  The two textures and flavors swirl together, one creamier and one more intense.  Creating this flavor experience for yourself—and those you love, if you love them enough to share—is priceless.  Or at least it’s worth the price of a chocolate thermometer.

Chocolate Truffles with Fresh Mint

Adapted from Pure Chocolate by Fran Bigelow.  You can make truffles the traditional French way and sidestep the tempered chocolate completely for an easy yet elegant indulgence.  The mint is also optional; without it, the chocolate truffles are pure, deep and will showcase the flavor of whatever chocolate you use.  With the mint, you taste clear notes of a fresh garden in contrast to the dark chocoloate.

Ingredients:

  1. 12 ounces semisweet chocolate--best quality available
  2. 1 ½ cups heavy cream (you only need 1 cup if making recipe without mint)
  3. 3 T unsalted butter
  4. A very large handful of fresh spearmint leaves
  5. 1 recipe of tempered semisweet chocolate (optional)

Directions:

  1. Using a sharp knife (many people find it easiest to use a serrated knife for this), chop the chocolate into small and relatively uniform pieces. It’s easiest to make a cut every few millimeters, chopping from the corners, rotating every few cuts.   Transfer the chopped chocolate into a heat-resistant bowl.
  2. Bring the cream just to a boil in a small saucepan.  Add the mint leaves—enough to fully inundate the cream—and stir the leaves so that they are fully covered by the cream.  Cover the pan and let steep for a half an hour.  (To intensify the mint flavor, you can put the mint and cream in the refrigerator overnight after steeping.)  Remove the mint leaves, and return the cream just to a boil.
  3. Pour ONE CUP of the hot cream over the chopped chocolate and let it sit for one minute.  With a rubber spatula or wooden spoon, stir the cream from the center, gradually working your way outward until all the chocolate is melted and incorporated into the cream.  You don’t want to whisk or whip the mixture; the goal is to make the smoothest emulsion possible. 
  4. Cover the ganache with plastic wrap so that the wrap is touching the surface of the ganache.  Let it stand overnight (or for at least 8 hours) at room temperature to allow the flavors to meld.  This step also improves the ganache’s consistency for rolling into shapes.
  5. In preparation to make the truffles, set out your butter early so that the butter will be at room temperature when mixing it into the ganache.  They should be approximately the same temperature as each other.  In a separate bowl, beat the butter until it is soft.
  6. Carefully fold the butter into the chocolate, fully incorporating the butter until you have a glossy, smooth ganache.
  7. When making truffles, smaller is better.  You should be able to eat the truffle in no more than 2 or 3 small bites.  To make the truffles, you have a couple of choices.  You can put the ganache into a pastry bag fitted with a ½ -inch round and pipe the ganache into 1–inch spheres onto a parchment lined sheet pan, and place the truffles in the refrigerator to set.  Later, slice off the “tails” left by the tip.  Instead of using a pastry bag, you can also cover the ganache, refrigerate it for 20 minutes, and scoop the ganache out by teaspoonfuls, or with a small melon baller, then finish shaping the ganache into rough 1-inch spheres with your palms, placing them on the paper-lined pan.
  8. At this point, you can opt to use the traditional French method for truffles and roll the balls in cocoa powder.  If you choose to make this type of truffle, it’s best to eat the truffles within a few days.  Store them in an airtight container in the refrigerator. 
  9. If you wish to enrobe the chocolates in a crisp coat, follow the directions below for tempering chocolate and dipping truffles.

Makes about 60 truffles

Tempering Chocolate 

Ingredients and Equipment

  • 2 pounds good quality semi-sweet chocolate (Fran recommends 56% cacao.  I use Callebaut semi-sweet in large blocks, found in the bulk section of one of those more expensive grocery stores. It contains slightly less cacao than she recommends, but it still works beautifully)
  • A chocolate tempering thermometer (not a candy thermometer; it will not register low enough temperatures)
  • A double boiler (or stainless bowl that fits into a saucepan without touching the bottom)

Directions:

  1. Set aside about half a pound to use later.  Chop this reserved chocolate into chunks. 
  2. If you are dipping chocolate truffles and have been storing them in a cooler spot, make sure they are sitting out at room temperature while you are tempering the chocolate so that they don’t lower the tempered chocolate’s temperature too much.
  3. Chop the remaining chocolate into small pieces, and place the pieces in the top of a double boiler, with the water level in the bottom pot NOT touching the top pot.  Rather than using a double boiler, I use a stainless bowl over a small pot filled with about an inch of water (not touching the bowl).  It is essential that no water touches the chocolate or even the base of the bowl (which will make the chocolate heat too fast). 
  4. On low heat, slowly heat and stir the chocolate with a dry spoon or paddle until it reaches 115˚, which is high enough to break the crystal structures.  Do not exceed 120˚.  When chocolate gets too hot, the cocoa butter separates from the solids.
  5. Remove the chocolate from the heat.  Add the reserved chunks of “seed” chocolate and stir them into the melted chocolate so that the chunks melt into the chocolate.  Cool chocolate until it reaches 82˚ - 84˚.  Remove chunks from the melted chocolate, if any remain.
  6. Return the bowl or pot back to the simmering water for a brief period until the chocolate reaches 88˚ - 90˚.  This takes only a few seconds.  Do not let the temperature exceed 90˚ or it will likely lose its temper. If this does happen, you can repeat the process from step 4.  
  7. You can test to see if the chocolate is tempered by spreading a small amount of chocolate onto parchment.  If it sets up to a glossy finish in a couple of minutes, then it is in temper.   You are now ready to dip.

Provides coating for about 100 truffles or other small centers

Dipping into Tempered Chocolate

  1. There is more than one way to dip truffles so that they are evenly coated.   One method, as detailed in Fran Bigelow’s book, is to drop the truffle into the tempered chocolate with one clean hand so that it is completely submerged, then remove it from the melted chocolate with your other hand, gently shaking off the excess.  Fran also mentions that you can use a dipping or dinner fork to lift out the chocolate centers.  Another method that my chocolatier friend showed me involves having some of the chocolate in one of your immaculately clean palms.  Pick up a truffle and place it into your chocolaty palm, then roll it around in your palm to make a thin coat all around the truffle.  Whichever method you choose, work rapidly to avoid affecting the temperature, and place coated truffles on a parchment-lined pan or plate. 
  2. After you dip all of your chocolate truffles, you will have leftover chocolate to dip into, so you can use the opportunity to experiment with dipping other foods into the chocolate before the chocolate is no longer in temper.  You could also pour the leftover tempered chocolate into molds. If you are dipping something that doesn’t require complete enrobing, such as candied orange peel or pretzels, you can just dip the item directly into the chocolate, gently shake off the excess, and place it on a parchment-lined pan.
  3. Save any leftover chocolate by pouring it onto a piece of wax paper or parchment, let the chocolate cool completely, then peel off and break up the chocolate.  Store in an airtight container in a cool place.  Use this chocolate for baking. 
  4. Store truffles in an airtight container.  The truffles will taste best within a week, but they can stand airtight storage in a cool, dry place for quite a bit longer than that.

Main information sources:

http://en.wikipedia.org/wiki/Chocolate

http://www.chocolatealchemy.com/

Pure Chocolate by Fran Bigelow