Academic Minute Podcast

Caitlin Clark, Colorado State University – Chocolate Flavor Through Fermentation

On this Student Spotlight: Fermentation isn’t just for alcohol.

Caitlin Clark, Instructor and Ph.D student in the department of food science and human nutrition at Colorado State University, discusses another dietary favorite that makes use of this process.

Caitlin is a Ph.D student and chocolate researcher at Colorado State University. Her research in the Food Science program focuses on cacao fermentation and post-harvest processing techniques.

After earning a B.A. in Linguistics and Classical Languages at the University of Colorado, Boulder (2005), Caitlin lived in Madrid, Spain, working at the Spanish Department of Defense and other government agencies. She was drawn to fermented foods during her time in Spain, where she was exposed to traditional, time-honored practices of food preservation.

Caitlin returned to Colorado and achieved a M.S. in Food Science from Colorado State University in 2019. This research was published in Scientific Reports as “Effects of Time and Temperature during Melanging on the Volatile Profile of Dark Chocolate”. Her work as a Ph. D candidate focuses on the breakdown of cacao proteins under fermentation conditions. Caitlin has been asked to present her work at the Craft Chocolate Experience (2020) and the Lillian Fountain Smith Conference (2021). She expects to complete her Ph. D in 2022.

In addition to research through Colorado University, Caitlin has participated in external research projects for the Heirloom Cacao Preservation Fund and gained industry experience as a chocolate-maker and farm consultant. Her teaching experience includes courses on Food Fermentation, Food Chemistry, Brewing Processes, and Sensory Evaluation.

Having already dedicated several years of research to cacao flavor, Caitlin hopes to build a career working with chocolate makers and cacao farmers on improving the quality of their product. At home, she practices belly dance and is a terrible, but enthusiastic, cook.

Chocolate Flavor Through Fermentation


Are you a chocolate-lover? Even true chocoholics might not know what their favorite treat has in common with yogurt, cheese, and wine: its flavors come from fermentation. Fermentation is the process of improving a food through the controlled activity of microbes.

The food you know as chocolate starts its life as the seeds of football-shaped fruit. Farmers scoop out the seeds and pulp into piles or boxes. The seeds are now called “cacao beans”. They ferment for about a week before they’re dried, roasted, then crushed with sugar until smooth and ready to eat.

So, let’s go back to that fermentation step. Cacao fermentation is a multi-stage process. The first stage involves yeast. Just like the yeast in your beer, yeast in a cacao fermentation produces alcohol by digesting the sugary pulp around the beans. As the pulp breaks down, oxygen enters the fermentation and oxygen-loving bacteria take over. The bacteria generate acetic acid from the alcohol that the yeast produced. Acetic acid causes biochemical changes as it soaks into the beans, and that has a major impact on flavor. Finally, as the acid slowly evaporates and sugars are all used up, spore-forming organisms begin to grow.

Cacao is a wild fermentation. Farmers rely on natural microbes in their environment to create unique, local flavors. This phenomenon is known as “terroir”. Makers of gourmet, small-batch chocolate hand-select cacao beans based on their distinctive terroir to produce chocolate with an impressive range of flavor nuances.

For example, one bar may be reminiscent of raspberries, while another has notes of toffee and raisins. Yet in both cases, the bars contain nothing except cacao beans and sugar. These impressive flavor differences are due almost entirely to the power of microbes.

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