Physico-Chemical Analysis of African Hazelnut Shells “ Coula edulis ” from Cameroon

Abstract

This work aims to characterize the physical, chemical, and thermal properties of hazelnut shells of the “ Coula edulis ” variety, originating from the south of Cameroon. The samples were divided into two zones (polar and equatorial) to study absorption and drying under four isotherms. The analyses allowed for the determination of the diffusion coefficient, the corrected diffusion coefficient, the relative humidity rate (RHR), and the activation energy using the gravimetric method. The results show that the relative humidity rate (RHR), of the polar region is higher than that of the equatorial region, while the diffusion coefficients and corrected diffusion gradually decrease. Among the models tested, the Page model best predicts humidity variations, while the Newton and Lewis models stand out for describing the drying phenomenon. “ Coula edulis ” has a dense structure with low porosity and limited water absorption, demonstrating their mechanical strength and dimensional stability. FTIR analysis highlights the presence of major lignocellulosic compounds (cellulose, hemicellulose, and lignin), while XRD reveals moderate crystallinity associated with mineral phases. ATG/DTG confirms good thermal stability up to high temperatures. These properties position the “ Coula edulis ” shells as a promising material for applications in bio-composites, thermal and acoustic insulation, or even as sustainable materials with a view to a circular economy.