Process effect on couscous quality

Commercial and traditional homemade couscous are both produced by the agglomeration process. Each couscous granule represents an aggregate of several semolina particles. Couscous manufactured by this process lacks a definite uniform shape and size. The objective of this study was to produce couscous with more uniform shape and size using extrusion technology. High-temperature short-time twin-screw and low-temperature single-screw extruders were utilized. The extruded and agglomerated couscous were evaluated for color, water absorption index, water solubility index, degree of starch gelatinization, cooking quality, and sensory attributes. The twin-screw-extruded couscous was characterized by its shape and size uniformity, its intense yellow color, and its high degree of starch gelatinization. This product also showed significantly higher water absorption, shorter rehydration and cooking times, and better appearance, flavor and overall acceptability than that of the agglomerated couscous (commercial and homemade). The single-screw extruded couscous was also uniformly sized but had excessively long rehydration and cooking times due to its dense and compact texture. In addition to its poor cooking quality, this product showed the highest water solubility index and was poorly rated for most of the sensory attributes tested.