Irene Chetschik, the Chocolate Alchemist

Irene Chetschik, how does one become a chocolate chemist?

Almost twenty years ago, I completed a PhD in food aroma chemistry at the Technical University of Munich, Germany. Afterwards, I worked for five years for various private companies in Switzerland and Europe, but I missed the freedom of academic research. That's why, when the opportunity to return to this environment arose, I didn't hesitate. That's how I ended up at the Zurich University of Applied Sciences, ZHAW.

My scientific work involved setting up analytical tools to characterize chocolate aromas at the molecular level. I carried out this work as part of a project in collaboration with a company that manufactured chocolate using a new process. With my tools, my team and I were able to characterize many chocolates made with the new process or traditional ones, and from different cocoas. It was very interesting to see that many odor-active components were present in all chocolates. Only their abundances changed, thus creating the different aromatic profiles. From a sensory point of view, they could be described as fruity, floral, or intensely cacao-like.

That gave me the idea to create a kit of key cocoa aromas. It contains the twenty-five main molecules responsible for chocolate aromas. It is, in a way, the aromatic DNA of cocoa and chocolate. Indeed, these components are always present, but in different quantities. This is a consequence of the different varieties and origins of beans, as well as the processing steps along the cocoa value chain.

Kit for training in sensory analysis of chocolate developed by Irene Chetschik and her colleagues at ZHAW. Photo credit: ZHAW.

Given the gustatory complexity of cocoa, 25 components seems few. How did you identify them?

Indeed, these are the 25 main volatile compounds characteristic of chocolate. In reality, there are nearly 600 different volatile molecules detected in various cocoa products and chocolate. However, not all of these molecules contribute significantly to the overall aroma of cocoa and chocolate. Moreover, the sensory receptors in our nose react to only a small fraction of these molecules to produce the taste of cocoa and chocolate. This is a small number for such a delicious flavor.

To detect the key components, we use a technique called gas chromatography-olfactometry, abbreviated GCO. With the help of human noses, this method allows us to identify the elements that play an active role among the odorless ones. Indeed, our nose is still one of the most powerful detectors. Thus, humans can easily detect certain compounds present in trace amounts – on the order of parts per billion, or even less. In comparison, even a very sensitive measuring instrument struggles to do so.

Irene Chetschik, how do people participating in the research recognize the "good" chocolate molecules?

Indeed, this approach involves training people to recognize odor compounds. That's what our kit is for. Thanks to this training, GCO analysis of chocolate samples allows us to identify the presence of active components. This step is essential to decode the aromatic profile of cocoa and chocolate at the molecular level. Thus, we can understand which compound is most important in the overall impression of a product.

Similarly, we can also detect which odorant element is the most powerful in raw ingredients. Thanks to this, and by quantifying the element, we can get an idea of how the ingredient has been processed. This is why the kit can also be used to train a panel of tasters. This makes it possible to recognize the specific flavors of cocoa and chocolate samples. At ZHAW, we also use it in our courses explaining the creation of aromas throughout the cocoa value chain.

 Irene Chetschik analyzes the volatile compounds of chocolate after separating them using the GCO method. Photo credit: ZHAW.

Chocolate aromas seem well-known; are there still research topics to explore?

Of course. For example, we are preparing a funding application for a new project. We want to apply our methodologies to different varieties and origins of cocoa. The goal is to understand their influence on the flavor profile of cocoa and chocolate.

Furthermore, we have started to study the aromatic constituents of Theobroma grandiflorum seeds, which could be used as a substitute for cocoa. With cocoa prices skyrocketing this year, the industry is looking for alternatives that can produce the same delicious taste as cocoa. Additionally, Theobroma grandiflorum is a cousin of cocoa believed to be more drought-resistant.

In addition, we continue to work on a method called cocoa incubation. The goal is to find an alternative to traditional fermentation after harvesting. The current process is laborious and difficult to control. In contrast, cocoa incubation is easy to replicate and produces beans with low bitterness and a high intensity of fruity and floral notes. Beyond cocoa, we are also interested in vanilla and the odorous compounds of hemp, as well as plant-based alternatives for eggs. Our methods apply to all kinds of basic ingredients.

Finally, aren't these researches too subjective when it comes to evaluating the sensory properties of a product? Everyone perceives tastes in their own way...

I see our work as a tool to understand the aromatic profiles of different foods at the molecular level. Even though taste is subjective, there are specific molecules responsible for the perception of a specific flavor. Our task is to understand which component plays a role in this perception. This knowledge is useful for developing and improving new processes and products.

Moreover, in several of our experiments, by preparing taste models based on our data, we have shown that the odor profiles of raw ingredients could be successfully reproduced. Thanks to our research, certain controversies, such as the influence of odorless components on human perception, have been resolved, at least in part.

Irene's work is inspiring. Based on her sensory kit, I created a poster on the origin of chocolate aromas. It helps enthusiasts understand the impact of manufacturing steps on the taste of a bar. Available at Nicolas's shop. 

Sommelier Nicolas Filippov's note

Irene Chetschik, between chocolate and science. As brilliant as she is passionate, the chemist builds a bridge between understanding cocoa and our pleasure in transforming and eating it as chocolate. The researcher impressed me with her commitment. Analyzing smells has become second nature. She continuously trains her sense of smell, like a game. And after all these years, she still finds cocoa relaxing. By her own admission, it's not an easy feat. The PhD students she trains in sensory analysis often struggle with the painstaking work it requires. If perfumers' noses were to have their equivalent in the world of chocolate, Irene Chetschik would undoubtedly be the embodiment.

Read the article on the Nicolas blog.