Fermentation effects on physical, microstructural, cooking and sensory characteristics of a traditional Algerian couscous based on fermented wheat Lemzeïet

Couscous Lemzeïet is a traditional food prepared from fermented durum wheat in Algeria. The study aims to assess the influence of fermentation conditions (fermentation time and vinegar addition) on couscous Lemzeïet characteristics. Eight samples of couscous were characterized in terms of physical properties (particle size and shape distribution, color, and water sorption kinetics), microstructure, cooking quality (swelling index, disintegration degree, water holding capacity, and optimal cooking time), as well as sensory attributes (color, odor, stickiness, firmness, and overall impression). The results showed that size descriptors were similar whatever the fermentation conditions. Couscous particles were generally regular, homogeneous, spherical and non-convex, despite the effect of fermentation time on all shape descriptors except aspect ratio. Increasing fermentation time decreased yellowness, redness and increased browning index. Microstructure highlighted almost the same morphology for all samples. However, vinegar addition seems to increase inter-particle pores and decrease lipid droplets. Fermentation time increased disintegration degree, while vinegar addition caused the reverse effect as well as increasing swelling index (after 3 and 6 months of fermentation) and decreasing cooking time (after 12 months of fermentation). Sensory evaluation showed that increasing the fermentation time increased color, odor, and overall impression, and decreased stickiness. Vinegar addition increased odor and decreased color, firmness and overall impression. Fermentation conditions have an impact on couscous Lemzeïet features by modifying its physical properties, cooking quality and sensory attributes.