The Chemistry of Cocoa: Unlocking the Secrets of Flavor

Over the years, cocoa has become one of the most favorite delicacies across the world. Its value and quality are related to complex flavors and unique sensory properties. To better understand the cocoa flavor and the manner of obtaining the product with desired flavor, it is necessary to study the relationships between all chemical components that play a role in cocoa flavor, their sensory properties, and the source of flavor formation [1,2].

Fig 1. Cocoa beans.

Nonvolatile compounds

Various chemical components from cocoa beans participate in the formation of specific cocoa flavors. These components are alkaloids (methylxanthines), polyphenols, proteins, and carbohydrate (Fig 1.). Cocoa contains about 4% methylxanthines with theobromine (3,7-dimethylxanthine) as the major alkaloid of cocoa constituting 2% to 3% Other alkaloid found in cocoa is caffeine (1,3,7-trimethylxanthine) in small amounts (0.2%, and theophylline as traces. These compounds contribute to the typical bitter taste of cocoa [3].

Cocoa is a rich source of polyphenols which contribute significantly to astringent and bitter sensations. There are 3 main groups of polyphenols in cocoa: catechins (represented by (-)-epicatechin in Fig 2.), anthocyanins, and proanthocyanidins [4]. Cocoa also contains free sugars and polysaccharides that involved in the development of typical chocolate flavor through Maillard reaction with amino acids and proteins [5].

Fig 2. Chemical structure of nonvolatile contributors to cocoa flavor

Volatile compounds

Cocoa volatiles are derived from aroma precursors generated during fermentation, roasting, and drying process. About 700 volatiles have been identified in cocoa flavor. They include several chemical compounds such as aldehydes, ketones, esters, alcohols, pyrazines, quinoxalines, furans, pyrones, lactones, pyrroles, and diketopiperazines (Fig 2.). Alcohols confer a fruity and floral aroma and sometimes give candy notes. Aldehydes and ketones produce malty and chocolate notes in cocoa [6].

The most important compound of volatiles in cocoa flavor is pyrazines. They display nutty, earthy, roasty, and green aromas. It contributes to the overall cocoa flavors. The second most important volatile compound are esters which confer fruity flavor and the typical cocoa flavor. Other components that affect cocoa flavor are furanones and pyrones that enhance flavor impression and confer pleasant caramel notes [6].

Fig 3. Chemical structures of volatile contributors to cocoa flavor

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Reference

[1] Fowler MS. 2009. Cocoa beans: from tree to factory. In: Beckett ST, editor. Industrial chocolate manufacture and use. 4th ed. Oxford: Blackwell Publishing. p 10–48

[2] Torres-Moreno M, Tarrega A, Costell E, Blanch C. 2012. Dark chocolate acceptability: influence of cocoa origin and processing conditions. J Sci Food Agric 92:404–11.

[3] Franco R, Onatibia-Astibia A, Mart ˜ ´ınez-Pinilla E. 2013. Health benefits of methylxanthines in cacao and chocolate. Nutrients 5(10):4159–73.

[4] Misnawi JS, Jamilah B, Nazamid S. 2003. Effects of incubation and polyphenol oxidase enrichment on colour, fermentation index, procyanidins and astringency of unfermented and partly fermented cocoa beans. Int J Food Sci Tech 38:285–95.

[5] Ho VTT, Zhao J, Fleet G. 2014. Yeasts are essential for cocoa bean fermentation. Int J Food Microbiol 174:72–87.

[6] Rodriguez-Campos J, Escalona-Buend´ıa HB, Contreras-Ramos SM, Orozco-Avila I, Jaramillo-Flores E, Lugo-Cervantes E. 2012. Effect of fermentation time and drying temperature on volatile compounds in cocoa. Food Chem 132:277–88.