An overview of the physical and biochemical transformation of cocoa seeds to beans and to chocolate: Flavor formation

Abstract

Chocolate is a widely consumed product worldwide due to its exquisite flavor, which comes from the unique and fascinating cocoa flavor. This flavor depends on little controllable variables such as the genotype and the agroecological niche, and on the other side, on postharvest operations: (1) cocoa transformation from seeds to beans that comprises cocoa seeds preconditioning, fermentation, and drying, and (2) the production of chocolate from the bean in which roasting is highlighted. Postharvest transformation operations are critically important because during these, cocoa flavor is formed, allowing the differentiation of two categories: bulk and specialty cocoa. In this sense, this article presents an overview of cocoa postharvest operations, the variables and phenomena that influence and control the physical and biochemical transformation from seeds to cocoa beans, and their relation to the formation of chocolate flavor. Moreover, research perspectives in terms of control and management of postharvest practices in order to obtain cocoa with differentiated and specialty characteristics "from bean to bar" are discussed.

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“…This was made possible by diffusion of these metabolites from the pulp into the beans. Whereas all these metabolites are directly or indirectly involved in redox balancing of the microorganisms involved, ethanol (mainly produced by the yeasts) and acetate (mainly produced by the AAB through cross-feeding on ethanol produced by the yeasts) are desirable metabolites for cocoa bean curing, as they avoid the growth of undesirable microorganisms in the pulp, facilitate killing of the embryo together with an increasing temperature in the beans, and hence indirectly contribute to color and flavor development in the beans through the activation of invertase, peptidases, glycosidases and polyphenol oxidase, which is determined by the pH decrease and temperature increase in the beans (De Vuyst and Weckx, 2016;Kongor et al, 2016;De Vuyst and Leroy, 2020;Santander Muñoz et al, 2020).…”

“…Cocoa fermentation and drying are key steps in the curing of cocoa beans to make them ready for the production of chocolate (Schwan and Wheals, 2004;Saltini et al, 2013;De Vuyst and Weckx, 2016;Pereira et al, 2016;Ozturk and Young, 2017;Castro-Alayo et al, 2019;Figueroa-Hernández et al, 2019;De Vuyst and Leroy, 2020;Santander Muñoz et al, 2020). The microbial communities involved in cocoa fermentation processes are mainly composed of yeasts (in particular Candida, Hanseniaspora, Saccharomyces, and Pichia species), lactic acid bacteria (LAB; in particular Lactiplantibacillus and Limosilactobacillus species), and acetic acid bacteria (AAB; in particular Acetobacter species).…”

“…Traditionally, cocoa fermentation processes are spontaneous, uncontrolled, on-farm processes (Schwan and Wheals, 2004;De Vuyst and Weckx, 2016;Pereira et al, 2016;Ozturk and Young, 2017;Figueroa-Hernández et al, 2019;De Vuyst and Leroy, 2020;Santander Muñoz et al, 2020). They usually consist of two phases.…”

“…Acetate overoxidation may again cause a pH increase upon prolonged fermentation. The effect of the temperature and pH shift, together with the flow of ethanol and acetate from the pulp into the beans, is responsible for the killing of the seed embryo, the destruction of the seed structure, and the activation of endogenous enzymes that give the final flavor and color of the cured cocoa beans, in turn influencing the flavor characteristics of the chocolates produced from the concomitant roasted beans (Schwan and Wheals, 2004;Afoakwa et al, 2008;Saltini et al, 2013;Kongor et al, 2016;De Vuyst and Leroy, 2020;Santander Muñoz et al, 2020).…”

“…In the past decade, the use of starter cultures for cocoa fermentation has been focused on enhanced pulp drainage, faster fermentation of the cocoa pulp-bean mass, and improved quality of the cured and roasted cocoa beans and the chocolates produced thereof. They enabled competitiveness with or inhibition of the background microbiota and improvement of the quality and sensory profiles of the end-products (Saltini et al, 2013;De Vuyst and Weckx, 2016;Pereira et al, 2016;Ozturk and Young, 2017;Castro-Alayo et al, 2019;Figueroa-Hernández et al, 2019;Mota-Gutierrez et al, 2019;De Vuyst and Leroy, 2020;Santander Muñoz et al, 2020). Therefore, several studies have been performed to select strains of dominant and/or beneficial yeast and bacterial species occurring during spontaneous cocoa fermentation processes to elaborate appropriate inoculation cocktails (Lefeber et al, 2010(Lefeber et al, , 2011Pereira et al, 2012;Moens et al, 2014;Samagaci et al, 2014a,b;Meersman et al, 2015;Visintin et al, 2016;Koffi et al, 2018).…”