This work was carried out in collaboration between four authors. Authors KBR and APM designed the study, collected samples from the field and performed the laboratory tests and produced a draft of the manuscript. Author YBYC checked the data for validity and carried out the analyses of the study.

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Edible films have been successfully used in the food packaging industry for several decades. Today natural polysaccharides, including cassava starch, are increasingly being used in the production of such biodegradable edible films and food packaging. In Cô te d'Ivoire, there are improved cassava varieties whose starches have not yet been tested in the production of biodegradable films. In this study, the optical and mechanical properties and the water solubility of starchbased composite films of four improved cassava varieties with added glycerol, peanut oil and soy lecithin were determined. Starch was obtained by cold water extraction from native cassava from the varieties Bocou 1, Bocou 2, Yavo and TMS. Films preparation was made bycasting method with cassava, glycerol (25-30 %), peanut oil (5-10 %) and soybean lecithin (0-5 %). Increasing the glycerol content, increased L*color value and elongation at break and decreased a*, b*, colourdifference (ΔE*ab) and tensiles trength of the composite films. Also, increasing the oil content from 5 to 10%, increased the opacity, b*, ΔE*ab, water solubility, elongation at break but decreased L*, a* and tensiles trength. Similarly, increasing the soy lecithin content from 0 to 5%, increased the opacity, L*, b* and ΔE*ab, but decreased a*, of the starch-based composite films. The results suggest an ideal formulation of 4% starch/25% glycerol/5% oil/5% soy lecithin for a film with optimum mechanical properties with low solubility.

Water sorption test of coffee (Arabusta) powder carried out under laboratory conditions are presented together with mathematical analyses of the moisture adsorption isotherms. Coffee powder moisture adsorption isotherms were determined within the range of 0.07-0.97 water activity at 29°C, using saturated salt solutions dynamic method. Sorption isotherms of coffee powder have a sigmoid sharp (type II). The data obtained were fitted to several models of two-parameter (BET, Hasleys, Kuhn, Chung and Pfost, Freundlich and Oswin) and three-parameter (GAB). A non-linear least square regression analysis was used to evaluate the models constants.In relation to the isotherm models the best models were Halsey (in the wide range of water activity) and Kuhn (in the range of water activity 0.07-0.5) obtaining minor values of % mean relative errors and higher correlation coefficient. Critical value of equilibrium moisture content of coffee powder corresponding to the aw equal to 0.6 was 34.6 g water per 100 g dry matter. These values are useful for storing conditions optimisation from the point of view of microorganisms growth and structural changes analyses. The monolayer moisture content values for BET were higher than those for GAB, these values are 22.14 and 2.57 g water per 100 g dry matter, respectively.

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