What's the big deal? Don't I just melt chocolate like melting butter?
Chocolate, the popular product manufactured by roasting, fermenting, and processing the beans of a cacao tree in combination with sugar (and milk in some cases), is a pretty amazing food. Chocolate (when used in the singular form typically refers to the basic ingredient, while the plural chocolates is often used to refer to candies made with chocolate as a primary ingredient) has a complex flavor that can change and develop as it melts. Since its melting point is just below human body temperature, this means that while eating chocolate, both the texture (as it changes from solid to creamy liquid) and its flavor gradually changes in the mouth. This low melting point does makes it very easy to melt. Unfortunately, chocolate can burn if heated over 200°F (95°C) which is very likely when heated directly over an open flame. This need not be a concern if the proper precautions are taken.
There are several easy ways to melt chocolate. I'll discuss two of the most useful ones.
The microwave oven method is the easiest but works best when using a small amount of chocolate (less than 1 pound). The chocolate should be in relatively small pieces (chocolate chips also work well), so if you're using chocolate bars or blocks, you'll want to cut the chocolate into smaller pieces first. Microwave in short bursts, about 30 seconds at a time, and stir between each microwave session to provide even heating. At some point, the chocolate will be warm and the pieces will hold their shape as you pull it out of the microwave oven, but they will be slightly shiny and mush as you stir it. Keep stirring and allow the residual heat to melt the rest of the chocolate. If done properly and gently enough on high quality tempered chocolate, this method can result in melted chocolate that is still tempered. Heat it too much and you'll lose the temper, so it's important to stop as soon as the chocolate is about to melt.
The double boiler method uses a little more equipment, but gives you the most control while melting chocolate. You can melt larger quantities of chocolate with this method and use larger pieces (up to 2 ounce blocks). Select a heat proof bowl to place your chocolate in. Put about 1/2-in. water into a pot and place the bowl on top of the pot. Make sure the bottom of the bowl doesn't touch the water. Now you have a double boiler.
Put the bowl aside and bring the water to a boil. If you're melting a small amount of chocolate, you can simply take the pot of water off the heat. If melting a larger quantity of chocolate, keep the pot on the heat and turn it down to a bare simmer. Place the bowl of chocolate on top of the pot of hot water and stir the chocolate using a silicone spatula until it has melted. Be careful not to allow any steam or condensation to enter the melting chocolate or it can seize. This is usually not a problem if you are watchful and have a lip on the bowl. You can remove the bowl from the pan whenever you need to slow down the heating process and place it back on to introduce more heat. This will prove vital while tempering.
When melted chocolate returns to solid form the cocoa butter in the chocolate forms a crystal structure. The strange (or cool depending on who you're talking to) thing about cocoa butter is that the crystal structure they take on depends on the temperature at which they are formed. If the chocolate is allowed to cool on its own, the crystals of fat will be loose, resulting in a chocolate that is dull in appearance, soft & malleable, and greasy to the touch. This loose crystalline structure has a slightly lower melting point than tempered chocolate crystals. If, instead, while cooling, the chocolate is kept at 88°F (31°C), the loose crystal structure will not form (88°F is above the formation point of the loose crystals). At this temperature the cocoa butter actually forms a dense crystalline structure. Holding the chocolate at this temperature and stirring will allow a whole bunch of these stable crystal structures to form providing a lot of seed crystals to form in the chocolate. When the chocolate is finally allowed to fully cool, if there are enough stable seed crystals, then the chocolate will harden into a very stable hard chocolate with a slight sheen, snap when broken, and will keep for months at cool room temperature. Tempered chocolate provides enough stability to be worked into a variety of shapes - sheets, painted onto leaves and peeled off, flowers, cups, and molds. It also helps prevent the cocoa butter from rising to the surface of the chocolate and blooming into unsightly light brown markings or coatings.
To temper, most chocolate books will tell you to fully melt the chocolate and then to pour 3/4 of the chocolate onto a marble slab and repeatedly fold the chocolate onto itself and smear it across the marble until the chocolate is a uniform 82°F (28°C). The chocolate is then returned to the remaining hot chocolate and stirred in. The final mixture is either reheated or the residual heat is enough to bring the temperature back up to 88-90°F (31-32°C). This technique is can be a bit tricky and requires a marble slab (or other large, flat, cool surface like a sheet of aluminum or upside down sheet pan), a plastic scraper for smearing the chocolate (a spatula will also work), and a chocolate thermometer (an instant read that can measure accurately to the degree like the Thermapen will also work fine). The chocolate needs to be worked sufficiently on the marble slab for enough seed crystals to form, so you have to work relatively quickly as the chocolate cools. A good way to tell when you've reached the right temperature and stage is to pay attention to the viscosity of the chocolate. When the chocolate begins to thicken a little, you've reached the point where seed crystals are forming and you should be able to reincorporate it into the rest of the chocolate. The tempered chocolate must then be kept at tempering temperature, 88-90°F (31-32°C) until used.
I find that the seed method (as described in The Professional Chef) is a little easier. Since almost all the chocolate that is sold is already tempered, we can use a piece of this already tempered chocolate as a plentiful source of seed crystals.
Melt the chocolate in a double boiler while stirring to ensure unform temperature.}?>
Once the chocolate has fully melted and reached a temperature of over 105°F (41°C), remove it from the heat. At this temperature, all the crystals, loose or stable, should be melted. Add a piece of unmelted chocolate to provide the seed crystals. This piece can be as big as 2 ounces (if you're melting a sizeable amount of chocolate) or can be chopped up into a few smaller pieces.
Stir until the chocolate's temperature enters the tempering range, 88-90°F (31-32°C). The chocolate should be kept at this temperature until used.
Specific Tempering Temperatures
Depending on the cocoa butter content of the chocolate and introduction of other ingredients, the tempering temperature of chocolate varies. Harold McGee's On Food and Cooking provides these values for the three broad categories of chocolate:
|Type of Chocolate||Tempering Temperature|
|Dark (no milk content)||88-90°F (31-32°C)||Milk||86-88°F (30-31°C)|
Note that although white chocolate does not contain any cacao solids, it is still subject to the same tempering procedures since it is made of cocoa butter.
Tempered chocolate can be stored for several months without blooming at constant cool room temperature, 60-65°F (15-18°C).}?>