Physicochemical Phenomena in the Roasting of Cocoa (Theobroma cacao L.)

Abstract

The quality of cocoa depends on both the origin of the cacao and the processing stages. The roasting process is critical because it develops the aroma and flavor, changing the beans' chemical composition significantly by chemical reactions induced by thermal energy. Aspects have been identified as the main differences between bulk cocoa and fine cocoa, the effect of time and temperature on the formation of the flavor and aroma, and the differences between conductive heating in an oven, convective with airflow, and steam flow. Thermal energy initially causes drying, then non-enzymatic browning chemical reactions (Maillard reaction, Strecker degradation, oxidation of lipids, and polyphenols), which produce volatile and non-volatile chemical compounds related to the flavor and aroma of cocoa roasted. This review identified that the effect of the heating rate on the physicochemical conversion of cocoa is still unknown, and the process has not been evaluated in inert atmospheres, which could drastically influence the avoidance of oxidation reactions. The effect of particle size on the performance of product quality is still unknown. A more in-depth explanation of energy, mass, and chemical kinetic transfer phenomena in roasting is needed to allow a deep understanding of the effect of process parameters. In order to achieve the above challenges, experimentation and modeling under kinetic control (small-scale) are proposed to allow the evaluation of the effects of the process parameters and the development of new roasting technologies in favor of product quality. Therefore, this work seeks to encourage scientists to work under a non-traditional scheme and generate new knowledge.

Fluidized bed roasting of cocoa nibs speeds up processing and favors the formation of pyrazines

“…Roasting is an important step that reduces the water content in cocoa nibs and produces desirable aromatic compounds (Rojas, Hommes, Heeres, & Chejne, 2022). Cocoa nibs are mainly roasted in large drum equipment at 110 to 150 • C ranging from 20 min to 2 h until the water content and water activity decrease to about 1% and 0.2 respectively (Rojas et al, 2022). This process causes a series of non-enzymatic chemical reactions, well known as the Maillard reaction.…”

From polyphenol to o‐quinone: Occurrence, significance, and intervention strategies in foods and health implications

“…These o-diphenols or o-triphenols can be easily oxidized to o-quinones. Rojas et al (2022) reported that epicatechin is the principal substrate in the enzymatic browning of cocoa beans, and catechin is more susceptible to oxidation than chlorogenic acid (CQA) in thinned peaches (Guo, Bi, et al, 2021). In addition, (epi)fisetinidol and (epi)robinetinidol, which only contain one hydroxyl group on the A ring but have the catechol or pyrogallol B ring, are also capable of generating o-quinones catalyzed by mushroom tyrosinase (Chedjou et al, 2022;van Rensburg et al, 2000).…”

“…Moreover, the acidic aqueous solution is not conducive to the presence of o-quinones but favors the conversion of o-quinones to their original phenolic compounds (Ma & Waterhouse, 2018), which results in the faded color of CQAQ solution. Rouet-Mayer et al (1990) studied the enzymatic browning in broken apple tissues and the pure solutions of catechin and CQA, respectively. The result indicated that o-quinone formed by catechin is darker and lighter in CQA solutions and broken apples.…”

Quinone reactivity: Investigation of their contribution to nonenzymatic browning

“…Nonenzymatic oxidation of polyphenols typically includes two pathways, autoxidation with oxygen and oxidation catalyzed by other quinones, respectively (Oliveira et al., 2011). Generally, polyphenols containing catechol or pyrogallol groups are readily oxidized to corresponding quinones, including catechins, epicatechins, caffeic acids, gallic acids, quercetins, anthocyanins, and their derivatives (Guo et al., 2021; Oliveira et al., 2017; Rojas et al., 2022), whereas monophenols, resorcinols, and substituted phenols are not prone to oxidation (Waterhouse & Laurie, 2006). Currently, few studies have compared the oxidation rates of different polyphenols.…”