Determination of the Gnetum africanum water sorption isotherms for use in the design of an adapted dryer

Abstract

SummaryThis work is a contribution to the study of Gnetum africanum by the determination of sorption isotherms necessary for designing a dryer adapted to this product. Experiments were carried out on selected leaves sold in local markets of the region of Ngaoundéré (Cameroun) to produce a homogenous sample. Proximate characteristics of G. africanum leaves were determined. Desorption–adsorption isotherms were determined by using static gravimetric method at 30, 40 and 50 °C for water activity ranging from 0.10 to 0.90. Results obtained show that on dry basis G. africanum contains 5.91% of lipids, 20.19% proteins and 69.92% of total sugar and about 2.76% ash. The sorption isotherms of G. africanum are of type II. Five different models were used to study these experimental curves and GAB’S model best describes these sorption isotherms (MRE < 10% and R2 > 0.996%). The sorption heat of the monolayer HM was 57.857 kJ mol−1 while that for the multilayer was 42.947 kJ mol−1.