Assessment of adsorption isotherms of three plantain flours (Musa paradisiaca L. var. Horn 1, FHIA 21 and PITA 3) and cassava flour (Manihot esculenta Crantz var. Bonoua 2)

Adsorption isotherms constitute an important source of information for establishing the stability of food products and their storage conditions. The aim of the work is to help reduce post-harvest losses of plantain and cassava in Côte d’Ivoire by manufacturing new products based on plantain and cassava flours. To achieve this objective, the static gravimetric method was used to determine the various experimental adsorption isotherms for the flours of three plantain varieties (Horn 1, PITA 3, FHIA 21) and cassava flour (Bonoua 2). They were modelled using the GAB equation. Adsorption isotherms were determined at a temperature of 28 ± 1°C in a water activity range (aw) of 0.11 to 0.90. The study showed a decreasing hygroscopicity for the four flours in the following order: Horn 1, PITA 3, FHIA 21 and cassava flour. The adjustment of the experimental values by the GAB model made it possible to estimate the various values of the monolayer. The water content of the monolayer (Xo) of the different flours (Xo (Horn 1) = 14.23 g H2O / 100 g, Xo (PITA 3) = 12.29 g H2O / 100 g, Xo (FHIA 21) = 11.40 g H2O / 100 g and Xo (Bonoua 2) = 9.49 g H2O / 100 g dry matter) corresponds to relative humidities of 11%, 11%, 10% and 11% respectively. The model fitted the four flours correctly, with correlation coefficients close to 1 and mean relative error of deviation values below 10 %. These values are optimal for ensuring adequate storage conditions for the different flours.