Development of a Novel Integrated Approach to Monitor Processing of Cassava Roots into Gari: Macroscopic and Microscopic Scales

Abstract

Gari is a key staple food in several western African countries. This is a cassava traditional semolina obtained after peeling, rasping, fermentation, pressing, sieving, and roasting (cooking/drying). The process of gari production is artisanal and relies on human know-how, and the final properties of gari are highly dependent on the human skills. So as to understand the combined effect of the various transformation steps on the final quality of gari, the main objective of this work was to develop a lab-scale integrated approach to follow the transformation of the product characteristics during the process using macroscopic (water content, solid volume fraction, and particles size) and microscopic (physicochemical and biochemical) responses. At the microscopic level, pressing is a key step insofar as it induces the draining of many soluble compounds (especially the toxic cyanogenic compounds). At the macroscopic level, despite the strong similarity in median diameters of the intermediate and final products, two distinct agglomeration mechanisms occurred during the pressing/sieving and the roasting. These mechanisms highlight the structuration of the product at two different scales and at two different moments. Finally, results showed a high swelling capacity for fermented gari. The approach developed in this work will make it possible to identify the robust mechanisms, i.e., those little affected by a change in scale or in operating conditions. This identification will thereafter allow to distinguish unit operations, fairly easy to mechanize, from those requiring strict control to achieve the final product quality sought.