Chocolate Tempering: Beyond the Purple Haze

(This article appeared in the Summer 2022 issue of Pastry Arts Magazine)

by Dennis Teets

Controlling Form V (Beta) Crystal Growth and Agglomeration 

If all a chef or chocolatier had to be concern about when tempering chocolate was getting sufficient Form V crystals, the purple haze, working with chocolate would be relatively easy. However, whether you are hand dipping caramels or managing a production line you realize that as important as getting a chocolate tempered is, being able to control the thickening of the tempered chocolate over the time you are using it is just as important. Understanding what is happening as a chocolate thickens is important when trying to keep a chocolate tempered and in a usable flowable condition during a chocolate project. 

What’s Happening: Agglomeration and Growth the Second Part of the Crystallization Process

The crystallization of the cocoa butter in a chocolate starts with the formation of pre-nuclei. These nuclei form as a chocolate reaches its point of being supercooled. This is the temperature at which the liquid fat will transform into a solid fat. More correctly it is the temperature where the cocoa butter in the fat system of a specific chocolate starts the nucleation process. This process temperature point will result in both Form V and lower melt forms of crystals being created. During this time frame crystallization continues as these nuclei come together to form clusters which then form actual crystals. These crystals then grow by the absorption of other pre-nuclei and lower melt crystals. Once sufficient crystals form in proximity of each other agglomerations are formed furthering the thickening process. Agglomerations and crystal growth affects not only the flow properties of the chocolate during usage but also some solidification properties such as gloss and mouth texture. The reason for this is larger crystals don’t pack as tight or melt as quickly as smaller crystals. The result is the more crystal growth you have the closer the proximity between crystals in the liquid phase and thus the more rapid thickening you will have. While crystal growth and agglomeration are complex subjects the key is to understand the longer crystals are allowed to grow rapidly the harder it will be to get growth back under control through the addition of heat.

Tests for Maintaining Flow Properties While Retaining Form V Crystals Throughout a Tempering Process

Instruments such as a temper meters are available to give a graphical readout that can be used to compare the relative temper of a chocolate either between time intervals of a specific batch to monitor change, between different batches of the same chocolate to ensure consistent processing properties, or to give tempering unit set-up information for different recipes or product. Temper meters graph the temperature drop of a sample, that is being cooled in a cold sink, over a period of time. The slope of the line is used as the primary determination of the state of a chocolate’s crystallization. The more negative the slope the more crystals that have been developed. The correct slope for a specific recipe needs to be determined according to the product’s characteristics after solidification. Once determined the slope can be used to compare future tempering processes for acceptability. However, these instruments range in price from about $6000 to greater than $20,000 and are thus not a practical method for comparing tempering processes for most people tempering chocolate.

In order to control the thickening process of a tempered chocolate two key characteristic must be monitored. The first characteristic is that there are sufficient Form V crystals to cause the chocolate to solidify with the desired characteristics of snap, gloss, smooth mouth melt, and release from a mold. The second, characteristic is that the chocolate has the desired thickness to get a high-quality finished product. The first characteristic can be objectively measured using a 5-minute refrigerator release test. The second characteristic can be objectively measured by monitoring the weight gain of a specific area using a 2 decimal point scale. Areas in which a chocolate thickness directly affects the finished quality of a product include air bubble holes from entrapped air, and in complete mold fill. Also an overly thick chocolate makes it difficult to maintain center to chocolate ratios or form a thin shell when dipping items. Other observable characteristics that indicate overseeding the chocolate include lack of gloss and difficulty with item releasing from a mold.

Wanting a low-cost method that could be used by most chocolate users I developed the following two-part test which is based on chocolate thickening and solidification. The usefulness of the thickness portion of the test depends on the user focus on the details of performing the test in a consistent manor each time. However, as indicated in the Table 1 when performed by t taking at least three readings per testing interval the method can give directional information that can be used to help determine, when used along with processing characteristics,  when to adjust temperatures or dilute the batch with untempered chocolate.

Thickness Test

 Items Required:

Spatula with dipping line (Figure 1) A scale the goes out 2 or 3 digits past the decimal point.

Measurement Instrument

Simply create a line on the spatula, Figure 1, across one or both sides of the spatula. This gives a consistent depth on the spatula to dip to and thus approximately the same coating area. The line used in this picture was made with a permanent magic marker for presentation purpose. A line could also be etched in the spreader using a cutting tool or by wrapping a piece of tape around the blade as an indication of how deep to dip into the chocolate. 

Measurement Process: 

1. Dip the spatula into the chocolate to the line. The blade during the dipping process should be as vertical as possible, Figure 3.

2. Scrape bottom of spatula on the edge of a cup, one swipe.

3. Wipe the bottom with a cloth or paper towel being careful not to pull chocolate from top side of spatula of when making the wiping action.

4. Place the spatula on a piece of parchment paper on the scale

5. Weigh and record weight.

6. Repeat at least 3 times.

7. Use average of weights when comparing to other measurement intervals.

8. After last weight, cool chocolate on spatula in the refrigerator for 5 minutes, temperature around 45̊°F.

9. The chocolate should release from the spatula at the end of 5 minutes when spatulate tip is bent to flex the blade, Figure 5.

10. If the chocolate does not release it means more seed needs to be created or added.

11. If the chocolate does release from the blade it should be ready to use. End grain (Figure 6 and gloss (Figure 5) are additional indicators a chocolate is well tempered.

Controlling the Flow Properties of a Tempered Chocolate 

There are two basic methods available to control the thickening of a tempered chocolate: Heat Input, Dilution with untempered chocolate. 

Method 1 Heat Input: This method adds heat to melt out excess crystals to increase the liquid phase of the chocolate. Using this method, once a chocolate is determined to be tempered (Release Test), the temperature is increased in small increments as you notice the chocolate thickening. The degree of increase will very over the usage time of the chocolate starting from very fine increments, as low as a 0.3̊°F and moving to larger increments as time in the tempering process lengthens. Using the above test allows you to be certain you are maintaining sufficient Form V crystals as you increase the chocolate’s temperature. 

Method 2 Dilution with untempered chocolate: Completely melted chocolate is added back to the tempered chocolate at a temperature close to the seed crystal melt out, 90 to 95°F,  temperature of the tempered chocolate. This method not only melts out large crystals but also adds non-crystalline fat giving more liquid phase to help reduce the crystal proximity to other crystals and thus grow rate. In general you can add between 1/3 and 1/2 of a chocolate back to a tempered chocolate at temperatures between 90 and 95°F. The actual amount and temperature range depends on the overall temper of the chocolate. This temperature will also depend on the type of chocolate being tempered. Not only does this method reduce the thickness of a chocolate but also expands the capacity. When using this method the unseeded chocolate must be well dispersed before using. If this is not accomplished streaking will occur.

For example: I worked with a dark chocolate that my initial temperature  at seed was 86.5F. As the chocolate thickened my first increment took the temperature to 86.8F. For my third adjustment I increase the temperature to 75.8°F. By the time I was done with adjust the temperature, my final temperature was 90F and I was adding back unseeded chocolate that was at 90.5̊°F at a rate of about 1/3 of the total batch size.  I was able to have a stable viscosity for 1 hour plus using this method. Unfortunately, this process is recipe dependent. However, by monitoring one’s process using the underlying concept explained in this article you should be able to extend the usable time of a chocolate substantially.

While agglomeration and crystal growth are very dynamic and interactive processes learning to utilize the 2 methods mentioned above in conjunction with the above test method will help you to extend both your use time, and capacity while maintaining your product quality.

About Dennis Teets

Dennis Teets has worked in the confectionery 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].