Desorption Isotherms and Isosteric Heats of Fermented Cocoa Beans (Theobroma cocoa)

Abstract

Water desorption isotherms of fermented cocoa beans from Ivory Coast were determined using the gravimetric static method of saturated salts solutions at 30 °C, 40 °C and 60 °C, and isosteric heats of desorption were calculated from Clausius-Clapeyron equation. The experimental data were fitted to several isotherm equations. The best fittings were obtained for the BET equation for aw<0.50 (with an average mean relative deviation (MRD) value of 1.56%) and for the Harkins-Jura equation for aw≥0.50 (with an average value MRD equation of 4.17%). The isotherms obtained at 30 °C and 40 °C are practically coincident and overlapped for aw below 0.40. Fermented cocoa beans presented a monolayer moisture content of 0.083 dry basis (d.b.) at 30 °C and this value decreases with increasing temperature. The net isostheric heats of desorption for fermented cocoa beans for the temperature range studied (30-60 °C) were estimated as a function of moisture content. The maximum net isosteric heat of desorption for fermented cocoa beans was estimated at around 13.51 kJ/mol corresponding to a moisture content value of 2.85%. The energy requirement for maintaining the moisture content low of 8.7% (d.b.) or 8% wet basis (w.b.) for safe storage of this product or for reducing the moisture content during drying was estimated at around 9.58 kJ/mol.

Water dynamics adsorption properties of dried and roasted cocoa beans (theobroma cacao L.)

“…From the range of water activities of 0.1 to 0.8, the equilibrium moisture content of the roasted cocoa beans increased with water activity at a given temperature, and the equilibrium moisture content decreased with the temperature at a given water activity. This behavior has been reported by Akmel et al [3] in fermented cocoa beans and is typical of many food products. In (Figure 1b), sharp increases in the moisture content at a w > 0.5 at both 30°C and 40°C can be seen.…”

“…Water adsorption isotherms represent the relationship between the equilibrium moisture content and water activity at constant temperature; their knowledge is useful to establish proper storage conditions and to predict the shelf lives of products such as cocoa beans. [3] The adsorption process is a phenomenon that occurs on the surface of almost all solids and depends on several factors: the physicochemical properties of the adsorbent, the chemical characteristics of the adsorbates, the prevailing experimental conditions and the affinity between the adsorbent and the adsorbate. The adsorption capacity of the adsorbent can be related to functional groups, verified by Fourier Transform Infrared (FTIR) spectra, which can affect the adsorption efficiency of solids.…”

The prediction of moisture adsorption isotherm for sucrose powder in Côte d’Ivoire

“…According to the results shown in Table 3, two (BET and Kuhn) of the five models can be considered satisfactory for fitting that adsorption of sucrose powder (Figure 2 a and b), as they exhibited excellent values of R 2 and E%, respectively from 0.859 and 0.872; and from 7.7% and 3.4 %; these values are below the criteria recommended by Aguerre et al [30], where E% less than 10 % indicates a reasonable representation of the models, and by Labuza et al [31], in which the representation of isotherms is considered extremely good for E% less than 5%. These results were also in well harmony with those previously reported for grapes, apricots, apples and potatoes by Kaymak-Ertekin and Gedik [5] and for fermented cocoa beans (Theobroma cocoa) by Akmel et al [32]. It must be said that the Kuhn model was the best for describing the equilibrium moisture data within the water activity range.…”

Modélisation mathématiques du séchage artificiel (sous air chaud) de la pomme de cajou (<i>Anacardium occidentale</i> L.)

“…Le Tableau 3 présente des modèles empiriques décrits dans la littérature utilisées pour simuler la cinétique de séchage des produits végétaux et la nomenclature afférente aux modèles consignée au Tableau 4. Au nombre de huit, retenus pour cet exemple, ces modèles contiennent des paramètres et coefficients à déterminer à partir des données expérimentales du séchage (Akmel et al, 2009). La méthode du gradient a été développée sous un programme de calcul implémenté pour estimer les coefficients et paramètres à l'aide du logiciel MatLab R2016a (Griva, 2009 ;Abouo et al, 2015a).…”

“…La deuxième loi de Fick de diffusion a été largement utilisée pour décrire le processus de séchage pour la plupart des produits biologiques liant la teneur en eau du produit (M), la diffusivité massique (D), le temps (t) et la direction (z). (Robert et al, 2008 ;Touati, 2008 ;Akmel et al, 2009…”