Troubleshoot Chocolate Tempering
February 18, 2010
Recently I was asked about tempered chocolate that fails to keep a good shine and what can be done to fix that? (See comments on how to temper chocolate page.)
That's a really good question. Concerns about the streaking and the lack of shine make me think about how temperatures, crystal development and the appearance of chocolate are all connected.
Properly tempered chocolate is shiny and uniform in color. When chocolate has streaks and does not shine, it indicates that at some point in the production process, the chocolate solidified without being in a properly tempered state.
I am sorry to have to get technical here, but see if you can follow this. Cocoa butter has to solidify or form crystals within a narrow range of temperatures. Tempering means all crystals become as identical in size and shape as possible and we can do this by controlling the temperatures.
There are essentially 3 major stages in the making of chocolates that you have to be particularly careful to achieve the right temperature:
Stage 1 - The Starting Product
If you make your own chocolate candy center, like toffee or ganache, make sure it is absolutely at room temperature before you dip in chocolate. If you don't let it cool down enough, the heat will eventually push through your coating and cause it to lose its temper - either entirely or partially. On the flip side, if you let the center get too cold, you essentially “shock” the chocolate. This causes really BIG crystals to grow and the coating appears very dull, a flat finish.
If you mold your chocolates, use the molds at room temperature. This could be another source of unintended heat or cold introduced as the chocolate is solidifying.
Stage 2 - The Tempering Process
This is the most likely stage to produce streaking.
Agitating or stirring the chocolate during the tempering process is crucial to prevent streaking. Imagine adding red food coloring to white frosting to make it pink. If you stir in the coloring using only a few strokes, you will see streaks of red among the white. Continually stir and the frosting will eventually turn pink. Something similar happens when you temper chocolate without a thorough mixing. Temperatures along the bottom and sides of the tempering pan will be several degrees different than its center. Each temperature gradient grows different crystals at different rates. This causes light to bounce and bend irregularly and we see alternating streaks of light and dark chocolate after it dries.
Too much stirring will cause air bubbles to form and get trapped within the coating. Air bubbles cause crystals to form unevenly which gives the chocolate a grainy appearance on the surface.
If you use a tempering machine it may have separate milk, dark, and white chocolate settings. If not, you’ll need to set up the temperature and mixing parameters differently for each type of chocolate that you use. Milk chocolates temper at a lower temperature range than dark chocolates. Milk chocolates are tricky because there are different percentages of milk in any given brand or formulation of milk chocolate coating. The higher amount of milk (milk fat), the lower the temperature. White chocolates can be even more sensitive to temperature than milk chocolates.
Stage 3 - The Cooling Process
This is the most likely stage to produce dull looking product with no shine. The ideal temperature for cooling chocolate is between 65 and 68 F. The relative humidity should be 50% or less. I use a fan on a medium setting pointed right at my chocolates. The fan will lift the humidity out of the air surrounding them. Make sure the cooling tray is elevated off the counter top enough to let air circulate underneath and take away excess heat from the bottoms. A refrigerator hovers around 40 F and a freezer around 30 F – these temps are too low to encourage a nice shine. Rooms that heat up during the summer spell disaster for chocolate. Anything over 78 F is too warm and makes the chocolate soft and slightly sticky.
One obvious sign that the cooling process was unsuccessful is the formation of bloom. Bloom is a gray dusty film that covers the surface of chocolate. It can happen within hours, or days, after tempering and cooling.
To summarize, this particular tempering problem description appears to be a temperature issue at one of more stages of the process.