Processing cereals and legumes-based extruded foods using rheology and simulation

International audience

إنجليزي. Many starch-based foods, such as breakfast cereals, snacks, are produced by extrusion. There is a growing interest in diversifying the supply of balanced foods from local legumes. Legumes, composed of proteins (20-30% dry basis), dietary fibres (10-30%) and starch (40-50%), and low in sugar, are a sustainable source for human consumption. Despite nutritional advantages of legumes (high protein content, low glycemic index), extruded legume-based foods are still rare. Despite significant advances in extrusion modelling and simulation, the design of extruded products at the industrial level still relies on trial and error approach. A global 1D twin-screw extrusion model, implemented in a simulation software, Ludovic®, was used to predict flow variables along the screws and die, and to design starchy products with targeted structure and properties. An experimental database has been compiled with seven formulations for manufacturing extruded foods from starches, breakfast cereals, legumes flours such as pea and fava bean, and bran-enriched wheat flour. It includes thermal and physical properties of materials, melt viscous behaviour model, and experimental results on extrusion, ie. extruder configurations and operating conditions, and structure and properties of extruded foods.The extrusion model satisfactorily predicted product temperature at die exit (T) and Specific Mechanical Energy (SME). A sensitivity analysis of flow variables (T, SME, viscosity) was carried out on the formulation, extruder's configuration and operating conditions, generating extruder's working charts. The results established satisfying relationships between predicted flow variables and product features such as structural changes of starch and protein, density, cellular structure and functional properties. Extruder’s operating conditions leading to targeted food features are assessed from these relationships. Satisfactory correlations justified the use of the extrusion model as a computer-aided tool for designing extruded starchy foods, to predict food features and reduce time and labour costs in industrial foods R&D.