For me, the words “bread, chocolate, and coffee” conjure daydreams of a warm summer day, sipping espresso and indulging a Pain au Chocolat at a French bistro by the sea. But would you be surprised to hear that that same daydream is only possible because of microbes? Yes, those savory and sweet concoctions only make it to our cups and plates after spending some quality time with bacteria and yeasts.
This semester, students in USciences Applied Microbiology course will learn about the process of fermentation in producing bread, chocolate and coffee. Fermentation was, quite likely, “discovered” by accident in ancient times when a basket of grapes, left out for too long, was found to be not spoiled – but rather delightful. This same principle was then applied to many other types of food sources, including wet flour, cacao pods, and coffee cherries. While these fermentations have been taking place for centuries, it wasn’t until the 19th century that the cause of fermentation was actually identified as microscopic organisms – what were eventually identified as bacteria and yeast. The boon of cellular biology in the 20th century then allowed scientists to understand the chemical reactions that occur during fermentation – namely the breakdown of sugars into acids, alcohols, and gases.
In modern times, the process of mixing flour and water to make leavened baked goods has been largely industrialized and well-studied. Students in Applied Microbiology will conduct their own sourdough fermentations and test how farming styles – conventional vs. organic flours – impact the microbial ecology and physiology. Students will then manipulate their fermentations and learn how those decisions impact the final bread product from John McGrath, executive baker at Philly’s hometown café giant La Colombe.
Around mid-October, unbeknownst to many of us in North America, the late cocoa harvest will begin in the tropics. The cocoa used in chocolate is derived from the fruit of cacao trees, which harbor the cocoa beans, or seeds. At the beginning of the harvest season, students in the course will then receive cacao fruit and will proceed to ferment the beans, as cocoa farmers around the world do – they will leave it in a box for seven days. During this time, students will examine the microbial ecology and physiology and then correlate it to the presence of polyphenols – those compounds that have recently been touted as “making chocolate good for you.” Students will then be treated to a tasting panel at Hershey’s Technology Center, led by Master Chocolatier Jim St. John and hear the lasted in chocolate research and development.
Finally, as the colder weather sets in, students will begin their final fermentation of coffee cherries. When coffee cherries are harvested, the bean can undergo low, medium, or high fermentation, which will affect the final complexity and depth of the coffee itself. Because the beans are often fermented by the natural microflora found on the cherry, students will introduce specific “starter cultures” to identify what bacterial and/or yeast strains result in the most efficient fermentation. To experience how differing methods and styles of coffee fermentation affect the drink characteristics, students will participate in a ‘cupping’ – an official coffee tasting – at a local Philly café.
Through the semester, students will also be reading Simran Sethi’s cultural exploration “Bread, Wine, & Chocolate,” which takes a macroscopic view of many fermented foods (without going into too much microbiology), and even provides tasting guides – it’s a really fun read for anybody. By reading the book, students will not only be able to manipulate the microbes of their fermentations, but place into greater context how optimizing food fermentation interconnects with issues of biodiversity, sustainability, fair trade and their own experiences with food.
Students will be maintaining a blog of their research, which you can follow at www.fermentationstations.wordpress.com
Follow Dr. Stacey Gorski on Twitter @Dr_Gorski