(This article appeared in the Spring 2023 issue of Pastry Arts Magazine)
By Dennis Teets
In an earlier article we discussed the nucleation component of chocolate tempering and how to tell if a chocolate is tempered (see Figures 1-3 below).
In this article we will discuss what happens once nucleation occurs, and how to monitor and control the thickening of chocolate as the cocoa butter fat crystals in the chocolate move from nucleation to crystal growth and finally into agglomeration. While separated for the purpose of this discussion, nucleation, growth, and agglomeration occur simultaneously. However, as each stage develops, more intense heat input is required to break down the crystal structure created. Yet, at a certain temperature breakdown will occur very rapidly as the melting point of beta crystals is reached. This temperature varies with the type of chocolate but is generally between 87°F and 88˚F (30.5˚ and 31.1˚C) for a higher milk fat chocolate (white or milk) and 88°F to 91°F (31.1˚F to 32.7˚C) for a dark chocolate with no milk fat.
Why It’s Important
Learning to control the crystallization process when working with chocolate is important primarily because it affects how much time a person has to work with a batch of tempered chocolate. However, both over-crystallization and under-crystallization can also have negative effects on a solidified chocolate product. Over-crystallization, thick chocolate, causes issues such as incomplete mold cavity fill, prevention for air bubble release, and lower gloss or shine. Under-crystallization results in more difficult mold release, formation of feet on dipped or enrobed products, and reversion to lower melt forms, which can lead to bloom on solidification.
There are three sequential stages in the pre-crystallization of a chocolate. This process is commonly known as tempering. Each stage results in an increase in the thickness of the chocolate due to an increase in the number and size of crystals. Stage 1 is nucleation, which occurs with only a minor amount of thickening as crystals are very small and very few. This stage occurs either by beta crystal addition or beta crystal creation as supercooling causes the triglycerides to begin to align. Stage 2 is the growth phase, which occurs simultaneously once nucleation begins and causes the chocolate to thicken in a controllable fashion. This stage occurs due to the enlargement of the crystals by absorption of smaller crystals. This phase is relatively easy to control by the frequent addition of heat to keep crystals from growing quickly and thus thickening the chocolate. In Stage 3, nucleation slows down as the crystals become larger and crystals agglomerate. This stage involves the connecting of one crystal to another crystal.
Unless heat is added, these stages naturally proceed from 1 to 3, and will continue until the chocolate becomes too thick to use and – if at the right temperature – will solidify into a solid piece.
Monitoring Crystallization Over Time Visually
Evaluating flow is very specific to the project being performed. Thus, once a chocolate has been determined to be well tempered as defined by having the desired flow properties for a specific use, the goal is to keep it in that condition over the time of the production period. The most common way used to monitor crystallization over time is visual observation of the thickening of the chocolate. A few anchor questions to ask when visually monitoring flow changes include:
- Does the chocolate flow off the end of a spatula?
- When scraped on the side of a bowl, does the chocolate run down the side or stay in place?
- Does the chocolate coat the spatula evenly?
- Does the chocolate flow back together when divided by the spatula?
The key is to come up with questions that relate to the quality of the product being prepared.
Performing a Percent of Chocolate to Spatula Test
One measurement that can be used to get a more objective measurement of the thickening of a chocolate is to perform a percent of chocolate to spatula test and try to maintain that weight percentage over the time of use by increasing the chocolate’s temperature. In this test, a spatula is dipped to a standard depth line into the tempered chocolate pool. This line is marked in Figure 4 by the yellow tape around the spatula. The weight of the chocolate is determined by subtracting the weight of the spatula from the total weight of the spatula coated with chocolate. The chocolate weight is then divided by the total weight to determine the percentage of chocolate. This is the percentage you are trying to keep stable throughout the use process. Because of the many factors that affect the crystallization weight of a chocolate, this is an imprecise measurement, as a more crystallized chocolate may give a heavier weight or a lower weight depending on how the chocolate adheres to the dipping tool, and how precisely the chocolate is brought to cover the depth line at each test. As such, a range is acceptable as long as the finished chocolate product gives an acceptable product weight and finish, but thickening of the chocolate and weight change should be considered a sign to add heat to melt out some of the seed crystal.
The following table shows the results obtained from one such test. From this table we learn that chocolate weight gain percentage can be used to monitor weight change over a temperature range and thus can be used as an anchor for keeping a consistent chocolate flow over time.
Keys to Getting Repeatable Readings
- Stir the chocolate prior to taking the test to break up agglomerations.
- Start with a smooth flat surface.
- Ensure the item being coating is at a consistent temperature for each test performed.
- Handle separating coated spatula from the chocolate pool the same way every time a test is ran.
- Take a measurement of untempered chocolate to obtain a baseline.
Keys To Obtaining a Tempered Chocolate with Stable Flow Properties
The key to controlling a tempered chocolate’s flow properties is to recognize that crystal development and melt-out occurs at different rates in the different stages of the pre-crystallization process. In Stage 1, small changes in temperature are required to prevent the melt-out of actively forming nuclei and having an untempered chocolate. As crystals grow, more heat is required to maintain usable flow properties, as crystals in this stage are larger and thus require more heat to melt out. In the final stage, where agglomeration is occurring, even more heat is required to maintain usable flow properties. What makes this challenging is that these rates are not only affected by the stage of nucleation, but also the temperature of the environment contacting the chocolate and the chocolate formulation. For example, a dark chocolate with no milk fat will crystallize much faster than a milk chocolate.
Seven steps to assist in maintaining the flow characteristics of a chocolate include:
- Apply heat in short bursts.
- Check the temperature frequently.
- Allow temperature to equilibrate after each heat addition before taking next temperature reading.
- Keep chocolate on sides of container scraped into the chocolate pool.
- Keep bowl on insulated surface to prevent chocolate on bottom from thickening.
- Mix the chocolate frequently to ensure an even texture.
- Always run a temper test if chocolate has reached a temperature above 91°F (32.7˚C).
About Dennis Teets
Dennis Teets has worked in the confectionary industry for both large and small organizations for over 30 years. During that time, he was both a problem solver and a new product developer. Today, Dennis works as a coach and consultant for small to medium chocolate companies, focusing on growth, scale-up and problem solving. His email is [email protected].