This paper presents the results of thermophysical characterization of the powder resulting from the solar drying of Moringa oleifera leaves. The desorption isotherms of the powder, are determined by the gravimetric static method. The models of B.E.T, Smith, Henderson, Iglesias and GAB are used for the smoothing of the experimental points. The Clausius-Clayperon and GibbsHelmholtz equation are used for the determination of thermodynamic properties. The isotherms obtained are with type II. The theoretical curves of GAB present a better similarity with the experimental curve at 55°C. The monolayer moisture content (Xm) is 6.32 and 7. 24 % at 30° C; 5.13 and 6.3% at 35 °C; 5.1 and 5.9 % at 45 °C; 4.22 and 4.66 % at 55 °C respectively for BET and GAB models. Isosteric and entropic heats are more important for low values of moisture content. The activation energy of desorption of the powder in the range of temperatures tested is -10.1009539 kJ/mol. Isokinetic temperature (Tβ) and the mean harmonic temperature (Thm) are respectively 301.2435K and 300.12342K and the free energy (ΔGβ) is 302.18 J/mol. The desorption process of the Powder is non-spontaneous and is done by controlled mechanisms enthalpic.

Moringa oleifera leaves are increasingly used as a dietary supplement. The present study deals with the estimation of its thermophysical properties. It is based on the Clausius-Clayperon and Gibbs-Helmholtz equations. This study required knowledge of the sorption isotherms obtained by the static gravimetric method in the relative humidity range of 5.4 to 97% and the temperatures of 30, 35, 45 and 55 °C. The BET models (1938), Smith (1947), Henderson (1952), Iglesias (1981) and GAB (1985) are used for the smoothing of the experimental points. The isotherms obtained are of type II and characterized by a sigmoid shape. The theoretical curves of GAB and Smith show a better similarity with the experimental curves. The monolayer moisture content (Xm) is 8.54/7.62% at 30 °C; 7.0/5.52% at 35 °C; 6.74/ 5.41% at 45 °C and 5.45/4.65% at 55 °C respectively for the GAB and BET models. The net isosteric heat (qst) and desorption differential entropy (ΔS) tend towards zero for very high moisture contents. The activation energy of desorption of the Moringa oleifera leaves in the temperature range tested is -13.1010 kJ/mol. Isokinetic temperature ( β) and the average harmonic temperature (Thm) are respectively 314.172 K and 314.459 K while the free energy (Δ β) is 308.18 J/mole.

Gandaho et al., J. Appl. Biosci. 2017 Séchage du sorgho produit dans le Nord-Bénin : Caractérisation thermophysique et qualité microbiologique du produit séché 11016Journal of Applied Biosciences 112: 11016-11024 ISSN 1997-5902 Séchage du sorgho produit dans le Nord-Bénin :Caractérisation thermophysique et qualité microbiologique du produit séché (02) drying methods on the kinetic properties and microbiological quality of sorghum produced in North Benin. Methodology and results: Sorghum samples of the variety "tokobèssèmi" were dried under shelter and outdoors for (30) days in five (05) villages in the Department of Alibori. Thermical parameters such as the drying kinetics, the influence of relative humidity and air temperature drying on sorghum water content were determined. Microbiological analysis of samples of dried sorghum is paid to the determination of the total flora, yeast and mold, total coliform, fecal coliform and / or thermo tolerant and Staphylococcus aureus. The results showed that the increase temperature and a relative decrease in moisture from the drying air possible to obtain short drying times and low water contents of the product. The total flora of the sorghum samples is remarkable as well as total and faecal coliforms, yeasts and molds are also present. Microorganism's quality indicators such as Staphylococcus aureus were absent. Rates vary between faecal microbes 300-43 000 outdoor and 84-37000 indoors. The small total coliforms in Kandi are absent in the samples of other outdoor departments. They are almost absent under cover. Outdoor yeast number varies between 23 (Gogounou) and 92 (Malanville) while the mold of whatever density remains low at 41 to Gogounou. Under shelter these microbes are practically not observed. Conclusion and application of findings:Drying under a shelter in a farming environment apparently has an acceptable sanitary character for human food in view of the quality criteria as defined by the indicator microorganism.

Knowledge of the state of water balance of agro-food products is an essential step in drying or storage operations for preservation. Our study made it possible to determine the thermodynamic parameters which influence the storage conditions of fresh tomatoes grown in the south of Benin; and to predict its hygroscopic behavior during post-harvest storage. The desorption isotherms obtained at 40˚C, 50˚C and 60˚C, by the static gravimetric method using saturated saline solutions, are compared with those of the theoretical models of Brunauer, Emmet and Teller (BET), SMITH, PELEG and Guggenheim-Anderson-Boer (GAB). An adjustment of the experimental points, on the theoretical models, was made thanks to the numerical method which exploits the fminsearch algorithm under the MATLAB software, version R2018a. The GAB model at 50˚C faithfully reproduces the experimental desorption curves for water activities from 5.5% to 82.3%. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation, it increases when the degree of dehydration of the product increases. The applied isokinetic theory and enthalpy-entropy compensation are consistent.