The Chemistry of Chocolate Cocoa originates from beans of the cocoa tree and it is an important commodity in the world and the main ingredient in chocolate manufacture. Its value and quality are related to unique and complex flavors. Cacao tree or a theobroma cacao belongs to the Malvaceae family, it is tropical plant indigenous to the equatorial regions of the Americas. The fruits of the cacao tree are squash‐like pods that grow proximal to the trunk and to thicker branches and each cocoa pod contain about 35 to 50 beans embedded in a mucilaginous pulp. Chocolate is composed of cocoa solids, cocoa butter and sugar and at room temperature, it is in solid form. The melting point of a substance is the temperature at which it experiences a change, so it will turn from solid to liquid or a change from one common state of matter to another. One of the key reasons cocoa or chocolate melts in our mouth is because of the relationship of our body temperature and its melting point. Our body temperature is 98.6 degrees and the melting point of chocolate is around ten degrees lower. If you held a chocolate bar in your hand for too long, the chocolate will probably melt on your hand. If that is the case then chocolate will melt even faster in our mouth, unless we drank something cold, or out in the cold with our mouth open, usually between 75 and 80 degrees Fahrenheit, pretty close to the melting point of chocolate. As the cocoa reaches its melting point in the high 80 degrees Fahrenheit it will turn into a viscous liquid. In chemistry, the viscosity of a liquid is measured through the fluid’s thickness, and how slowly it flows. The particle size of the cocoa powder used in chocolate milk is 10–30 μm and ideally less than 0.5% of particles present that has a particle size above 75 μm. The distinctive smooth texture of cocoa or chocolates is achieved through the process of conching. Conching is a mixing process that evenly distributes cocoa butter within chocolate and may act as a polisher of the particles. It promotes flavor development through frictional heat, release of volatiles and acids, and oxidation. It produces smooth molten chocolate by breaking down lumps of ingredients into finer grains and reducing friction between particles. Without this process chocolate will have a gritty texture. This is because the ingredients form rough, irregular clumps that do not flow smoothly when mixed with cocoa butter using other methods. Cocoa liquor is used to produce chocolate through the addition of cocoa butter. The proportions of the different ingredients depend on the type of chocolate being made. The mixture then undergoes a refining process by travelling through a series of rollers until a smooth paste is formed. The next process, conching, further develops flavor and texture. An alternative to conching is an emulsifying process using a machine that works like an egg beater. After that mixture is then tempered or passed through a heating, cooling and reheating process. This prevents discoloration and fat bloom in the product by preventing certain crystalline formations of cocoa butter developing. Then mixture is put into moulds or used for enrobing fillings and cooled in a cooling chamber. Lastly the chocolate is packaged for distribution to retail outlets. References: Processing and Manufacturing of Cocoa. (2015). Retrieved from https://u.osu.edu/commoditychainofcocoa/processing-and- manufacturing-of-cocoa/. Relationship between Crystallization Behavior and Structure in Cocoa Butter. (n.d.). Retrieved from https://pubs.acs.org/doi/abs/10.1021/cg025580l. Aprotosoaie, A. C., Luca, S. V., & Miron, A. (2015, November 18). Flavor Chemistry of Cocoa and Cocoa Products-An Overview. Retrieved from https://onlinelibrary.wiley.com/doi/full/10.1111/1541-4337.12180. Singh, R. P., & Cook, L. R. (2018, November 1). Cocoa. Retrieved from https://www.britannica.com/topic/cocoa-food. Kotb, H. (Reporter). (2011, February 12). The Chemistry of Chocolate. [Television series episode]. NBC Learn. Retrieved from https://archives.nbclearn.com/portal/site/k12/browse/?cuecard=52212 Written by: Gemma J.
