The microwave is a widely available and easy-to-use tool for heating many types of foods. However, when you use it to heat chocolate, it is important to understand how the ingredients found in chocolate absorb the heat created in a microwave in order to prevent texture and flavor changes and to enable achievement of a specific melt temperature. Once someone understands how heat from a microwave is absorbed by chocolate, the microwave becomes not only a tool for melting chocolate, but can also be used to soften seed chocolate to a dispersible state for nucleation. That makes it practical for anyone with a microwave to create tempered chocolate items such as the Rice Krispies crunch balls seen in Figure 1.
Remember, seeding is the process of adding Form V crystals so the chocolate will solidify with the desired characteristics of a tempered chocolate product. Learning how to use the microwave to heat chocolate is a great addition to the skill set of anyone wanting to create tempered chocolate items without spending extra money on special equipment.
Controlling the temperature is critical in ensuring a tempered chocolate contains sufficient Form V crystals to solidify, so the chocolate is easy to handle and has a nice gloss. The key is to use heat sequences aimed at attain the three specific results that heat is used to achieve in a tempering process: complete melt-out of all of the crystals in a chocolate; a melt-out of the fat system until Form V crystals are free flowing enough to disperse throughout a chocolate to nucleate it; and controlled heating of a chocolate to a temperature that will both maintain Form V crystals and desirable flow characteristics.
The Three Crystalline States of a Chocolate During a Tempering Process
Before discussing how the microwave is used to control the temperature of a chocolate during the tempering process, we must develop a common terminology in order to define the three crystal states that we find in a tempering process. The first state is defined as the base chocolate. This is the fully melted chocolate that we’re going to temper. This chocolate has the easiest heat transfer. The second component is the seed chocolate. This component can be any previously well-tempered chocolate. This chocolate needs to be dispersed into the base chocolate at a temperature that retains Form V crystals, yet does not leave the chocolate with lumps. The third type of chocolate occurs when the seed chocolate is added to the base, creating nucleated chocolate. This chocolate contains sufficient Form V crystals to solidify with gloss, contraction, snap and the ability for us to handle it so it doesn’t easily melt.
The Four Stages of a Tempering Process
Every tempering process has four stages as it relates to heat input. Stage 1 involves a full melt-out of the chocolate to be tempered, so it has maximum flow characteristics and contains no crystals. This component is the base chocolate as defined above. Stage 2 entails the removal of heat to bring the base chocolate to a temperature at which Form V crystals will remain in the chocolate. Stage 3 involves the dispersal of seed chocolate defined in the last paragraph. In Stage 4, we maintain the chocolate at a temperature that allows it to retain both desirable flow properties and sufficient Form V crystals so it solidifies properly. While stage 2 requires heat removal, stages 1, 3 and 4 require heat addition and will be the focus of the rest of this article.
Understanding How a Microwave Heats Chocolate
A microwave heats chocolate through radiation energy, which stimulates the water molecules in the ingredients of the chocolate. This stimulation results in heat from the friction caused by vibration of the water molecules. Once you create heat in this process, conduction transfers heat from warmer particles to cooler particles. Also, as the chocolate becomes more fluid, convection transfers heat from warmer to cooler areas of the liquid mass. When we talk about convection, we mean the transfer of heat within a liquid material through hot areas rotating with cold areas. This happens because warmer areas are less dense than cold areas. This is the reason why utilizing the same amount of time at the same percentage of power results in an increased rate of heating during chocolate’s melting process.
Understanding How to Melt/Heat a Chocolate Without Creating Flavor or Texture Changes
There are two control parameters available to a chocolatier to control the heating of a chocolate: percent power and sequence time. Percent power is defined as the amount of time that a magnetron is on during a heating sequence. When you heat at 100% power for one minute, the magnetron is on for the full 60 seconds. Similarly, when you heat at 50% power, the magnetron would be on for 30 of the 60 seconds. During the off-time, heat transfers from one substance to another substance through conduction, leading to less heat buildup per heating sequence. The second parameter is the sequence time, meaning the amount of time the microwave is operating. This time can vary from one second to several minutes, depending on the amount of the item you’re heating and the melt state of the chocolate at the beginning of the sequence. The more liquid the chocolate being heated; the quicker the rate at which heating will occur.
Applying this understanding of how a chocolate heats in a microwave and the controllable microwave parameters provide the guidelines for choosing settings that limit the risk of developing burnt flavors and gritty textures, while providing the ability to control a chocolates temperature more precisely.
- Because the different ingredients in a chocolate respond differently to microwave energy, using full 100% power is likely to cause hot spots as well as flavor and texture changes if you don’t perform the process in very short time sequences. This is because heat can’t transfer easily from one ingredient to another, and different ingredients heat at different rates. Thus, it is recommended that you should use a lower percentage of power in order to allow for heat dispersion within a heat sequence. For the development of these guidelines, we chose a 30% power number, as it allowed us to use longer heat sequences without overheating any of the ingredients and creating a gritty texture or burnt-off flavor due to overheating of specific ingredients.
- Use multiple heat sequences in order to reduce the risk of heat concentration, since heat transfers more easily in a liquid than a solid.
- Reduce each new sequence length by 50% while maintaining the same percent power until the temperature is 105°F. This should allow for the incremental approach to a temperature with low risk of over shooting.
- When performing the full melt of a chocolate, use time sequences of 15 seconds or less when within five to 10°F of the desired temperature.
- Use five to 15 seconds when working with controlling the temperature and flow properties of a nucleated chocolate. A five-second heat sequence should raise a chocolate in the temperature range of 85 to 90°F about 1°F.
Process for Developing a Heat Sequence for Any Chocolate
The sequences outlined below were developed using 30% power in a 1250-watt microwave.
Complete Melt
- Start a one-minute heat sequence.
- Add one-minute sequences until chocolate begins to melt or reaches a temperature of 90°F.
- Reduce time sequence by 50% until chocolate is within 10°F degrees of the desired melt temperature.
- Use 15-second sequences until the temperature is within 5°F degrees of the desired melt temperature.
- Use five to 10 seconds per sequence, depending on the temperature increase needed, to achieve the desired melt temperature. When a chocolate is above 100°F, in general, you can expect a .5-to-1°F increase for each five-second heat sequence, with this temperature change increasing to 1.5 to 2.5°F increase at 10 seconds.
Desolidification of Seed Chocolate
You can soften chocolate sufficiently in order to disperse it, while retaining most of the chocolate’s Form V crystals by heating the chocolate to an overall temperature no greater than 90.5°F. You may add the desolidified seed chocolate to the base chocolate at any temperature between 86 and 90°F. After adding to the base chocolate, always check the now nucleated chocolate for temper prior to using.
- Determine the amount of seed chocolate to soften: Dark: 1 – 2%, Milk 2-3%, White 2-4 %.
- Start a one-minute heat sequence.
- Cut the time by 50% for each sequence until you achieve a temperature between 80F and 85F. Note: you can use any temperature chocolate between 84 and 90°F, as long as the chocolate is dispersible.
- Between 80F and 85F, use 10 seconds to increase the temperature by 1-3°F and 15 seconds to increase by 3 to 5°F.
Incremental Reheating of a Tempered Chocolate
- Heat the chocolate in five-to-seven-second sequences for each 2°F away from the desired melt temperature.
To learn more about how to melt, temper and reheat a chocolate in a microwave, please visit sweetanchors.podia.com.
(This article appeared in the Spring 2024 issue of Pastry Arts Magazine)
About Dennis Teets
After 30 years of working in the confectionery industry as a product developer, researcher, scientist, trainer, innovator, and consultant, Dennis decided to start a confectionery coaching website aimed at transferring the science behind confectionery processes into practical skills. With his deep knowledge of cocoa butter crystallization, Dennis helps students to understand what is happening in the physical process and how to control it. He hopes that knowing the science will free the student to explore the art and that more people will be able to enjoy freshly tempered chocolate products. To learn more about Dennis’ new adventure, please visit https://sweetanchors.podia.com/
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