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.
; Tel : (+225) 07259670 RESUME Les fèves de cacao sont des produits de plus en plus convoités par l'industrie agro-alimentaire et cosmétique du fait de leurs nombreuses vertus thérapeutiques. Ces produits sont généralement à hautes humidités ou à humidités intermédiaires d'où l'intérêt de leur stabilisation par le séchage. L'obtention d'un cacao bien séché qui satisfait les exigences du client nécessite la maîtrise de ce processus. Dans le but de mieux appréhender le séchage solaire, une modélisation a été effectuée. Un modèle mathématique de l'évolution de la teneur en eau des fèves de cacao a été réalisé à l'aide d'un réseau de neurones artificiel. Le réseau de neurones le mieux adapté est le perceptron multicouche avec deux neurones sur la couche d'entrée, deux neurones sur la couche cachée et un neurone sur la couche de sortie. L'application de ce modèle a révélé un écart minime entre valeurs expérimentales et valeurs prédites des teneurs en eau (X). Le coefficient de détermination R 2 de la régression linéaire entre valeurs observées et valeurs prédites des teneurs en eau (X) a été 0,99. Ainsi le modèle a présenté de bonnes prévisions et a servi à la simulation du séchage solaire de fèves de cacao. © 2018 International Formulae Group. All rights reserved.Mots clés : Séchage solaire, fèves de cacao, modélisation, simulation, réseau de neurones artificiel (RNA). Modeling the solar drying of cocoa beans by the Artificial Neural Network ABSTRACTCocoa beans are increasingly coveted by the food industry. These products are generally at high humidity or at intermediate humidities, hence the advantage of their stabilization by drying. Obtaining a well dried cocoa beans that meet the customer's requirements requires mastering this process. In order to better understand the solar drying, a modeling was carried out. A mathematical model of the evolution of the water content of cocoa beans was carried out using an artificial neural network. The most suitable neural network is the multilayer perceptron with two input neurons, two neurons on the hidden layer and a neuron on the output layer. The application of this model revealed a small difference between experimental values and predicted values of water contents (X). The coefficient of determination R 2 of the linear regression between observed values and D. KARIDIOULA et al. / Int. J. Biol. Chem. Sci. 12(1): 195-202, 2018 196 predicted values of water contents (X) was 0.99. Thus, the model presented good predictions and was used to simulate the solar drying of cocoa beans.
The purposes of this study were to compare the modalities of the post-harvest practices of these two groups and to statistically identify the modalities responsible of non-quality (under grade) on the basis of results of Pareto chart and proportion of successes calculated for each modality. A survey about of modalities of post-harvest processing methods and about the quality of the beans obtained was conducted among producers of the largest producing region of Côte d'Ivoire. The collected data were analyzed by the chi-square test of concordance and the Pareto chart. The results show that there is no correlation between practice of the individual farmers and the farmers in cooperatives. Highly significant differences (p-value < 0.001) were observed in the number of brewing; the fermentation time; the materials of fermentation and drying impacting the quality of merchantable cocoa. Samples collected from farmers into cooperatives have fewer defects than those of individual farmers. Regarding the modalities of the post-harvest practice responsible of the under-grades, the results showed that the samples of farmers in cooperatives had fewer defects than those of individual farmers. Thus, obtaining a good quality cocoa beans must take into account the best modality at each step of post-harvest practices. However certain modality should be avoided. These are: the time breaking pods of one day; the absence of brewing during the fermentation; the time of fermentation less than or equal to three days and the time of drying less than or equal to two days.
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