Kinetic Studies and Moisture Diffusivity During Cocoa Bean Roasting

Abstract

Cocoa bean roasting allows for reactions to occur between the characteristic aroma and taste precursors that are involved in the sensory perception of chocolate and cocoa by-products. This work evaluates the moisture kinetics of cocoa beans during the roasting process by applying empirical and semi-empirical exponential models. Four roasting temperatures (100, 140, 180, and 220 °C) were used in a cylindrically designed toaster. Three reaction kinetics were tested (pseudo zero order, pseudo first order, and second order), along with 10 exponential models (Newton, Page, Henderson and Pabis, Logarithmic, Two-Term, Midilli, Verma, Diffusion Approximation, Silva, and Peleg). The Fick equation was applied to estimate the diffusion coefficients. The dependence on the activation energy for the moisture diffusion process was described by the Arrhenius equation. The kinetic parameters and exponential models were estimated by non-linear regression. The models with better reproducibility were the pseudo first order, the Page, and the Verma models (R2 ≥ 0.98). The diffusion coefficients that were calculated were in the order of 1.26 to 5.70 × 109 m s−2 and the energy activation for moisture diffusion obtained was 19.52 kJ mol−1.

Quantitative Analysis and 2D/3D Elemental Imaging of Cocoa Beans Using X-ray Fluorescence Techniques

“…There are some gaps indicating tissue-free areas in these parts of the beans. Moisture diffusion and shrinkage effects inside the bean during the fermentation/drying process as possible causation have already been described by others in the literature. , Overall, the elemental maps obtained by means of μXRF are in good agreement with the data from the LA-ICP-MS approach . In the roasted bean, the embryonic region is not in the sectional plane; somewhat more faintly delineated are the structures of the cotyledon interfaces noticeable from the S, K, and Ca fluorescence intensity distributions.…”

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“…The value reported for willow stems match with the typical diffusion coefficients for humidity transport in wood, i.e., 1-5 × 10 −10 m 2 /s as reported by Baronas et al [47]. Studying dehydration kinetics of fermented cocoa beans, Adrover and Brasiello [48] found typical diffusion coefficients of 7.5 × 10 −11 m 2 /s at 25 • C. Domínguez-Pérez et al [49] found for roasted cocoa beans moisture diffusion coefficients in the range 1.26-5.70 × 10 −10 m 2 /s. For lemongrass, Nguyen et al [50] found effective diffusion coefficient in the range from 7.64 × 10 −11 to 1.48 × 10 −10 m 2 /s.…”

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

“…Several studies have investigated the kinetics of cocoa roasting processes in terms of water loss. Domínguez-Pérez et al (2019) found that the water loss was represented with a pseudofirst-order equation, and used the Arrhenius equation to find the temperature dependence. Hii, Menon, Chiang, and Sharif (2017) observed the typical exponential decay of cocoa's moisture content and reported the moisture diffusivities as a function of temperature.…”