Abstract
The wet agglomeration of durum wheat semolina is an important stage in couscous production which contributes to the final quality of the end products (couscous grains). There is still a lack of studies in investigating the agglomeration mechanisms of durum wheat semolina. The present study aims to investigate the agglomeration mechanisms occurring during the wetting/mixing process of durum wheat semolina. This process implies the mixing of semolina with different quantities of water in low shear mixers at fixed operating speed. The wet agglomeration mechanisms promote significant changes in size and textural parameters that have been investigated. The evolution in the diameter of the agglomerated structures (nuclei, agglomerates and dough pieces) composing the bed bulk, shows a continuous growth process associated to the expansion of their internal structure. Descriptions of the internal and the external structures of these elements are investigated by scanning electron microscopy. The evolution of solid volume fraction is depicted with respect to the water content at both bed bulk scale and agglomerate scale. At the bed bulk scale, a three-stage texturing phenomenon is identified. At the agglomerate scale, the evolution of solid volume fraction can be related to the evolution of the agglomerate size. The relation between the diameter and the solid volume fraction of the agglomerates can be modeled by a power law equation and could thus indicate that the agglomeration mechanism of durum wheat semolina is a fractal formation process