Students Test their Temper

Upper School scientists and chocolate fans had a hands-on lesson in the art of tempering chocolate when Sarah (Levy) Imberman ’99 and her Chief Operating Officer Alexa Sindelar visited Science teacher Gigi Mathews’ Chemistry of Cooking class to share their expertise.

In the days leading up to this visit, Mathews had been studying the chemistry of chocolate in class with her charges. She introduced the fats associated with chocolate, noting that triacyglycerol (a backbone glycerol bound to three fatty acids or acyl chains) is a major component of chocolate. She pointed out that the melting point of chocolate is linked to the triglycerides that compose it, and the more contact carbon chains of triglycerides have within a sample of chocolate, the higher its melting point.

Mathews encourages students to think of cocoa butter molecules as a long stick—like a Lincoln Log. Just like these toys, there are many ways for these molecules to come together, and some configurations are more stable and stronger than others. Just as stacking and interlocking each Lincoln Log with the ones below it produces a more stable structure, bringing chocolate to the proper working temperature while making sure the crystalline structure within the cocoa butter is still stable results in a more stable or “tempered” chocolate.

Tempered chocolate exhibits a shiny, glossy surface; has a creamy mouthfeel; breaks with a satisfying snap; melts less easily on your fingers; and sets up beautifully for dipped and chocolate-covered treats. Visiting chefs Imberman and Sindelar know tempered chocolate very well, as it is one of the primary ingredients in many candies offered on their website. When Mathews invited Imberman to demonstrate the process of tempering chocolate for students in her Chemistry of Cooking class, the business partners were happy to help.

On the day of the in-class demo, Imberman demonstrated the multi-step tempering process that each student group would replicate as part of that day’s lab, while Sindelar helped set up each student’s station. This process entailed first melting a specific amount of high-quality cacao pistoles to 122–131 degrees Fahrenheit, transferring a portion of this mixture to a holding vessel, adding more cacao pistoles to the melted chocolate, stirring them until they fully dissolved and the mixtures reached 82–84 degrees Fahrenheit, reintegrating the reserved portion of melted chocolate into the primary bowl until the mixture reached 88–90 degrees Fahrenheit and adding 1% of the total chocolate weight of Mycryo™ Cocoa Butter. Imberman pointed out that the Mycryo was the secret ingredient, which started a chain reaction resulting in perfect molecular crystallization, also known as tempered chocolate.

As students worked in groups to follow the instructions for tempering their own chocolate, Imberman and Sindelar went from station to station, offering advice and assistance. Digital thermometers, hair dryers, hot plates and heat pads were on hand to ensure students could reach the correct temperatures at each step of the process, and they took turns stirring and taking measurements of their mixtures.

With their tempered chocolate ready, students then used spatulas and Imberman’s time-tested “dunk, pump and slide” technique to coat marshmallows, graham crackers and strawberries.

The smells were decadent, the smiles delightful and all the tempered chocolate was poured onto parchment paper-lined baking sheets to enjoy and reuse after this experience.

Parker thanks Sarah (Levy) Imberman and Alexa Sindelar for sharing their time and talents with these students. More about their work is available here.

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Francis W. Parker School educates students to think and act with empathy, courage and clarity as responsible citizens and leaders in a diverse democratic society and global community.