Rheology and simulation for the processing of extruded breakfast cereals

International audience ; Many starch-based foods, such as texturized ingredients, breakfast cereals, snacks, crackers, pasta, noodles, and many others, are produced by twin-screw extrusion. Despite significant progress in process modelling, the design of extruded products at the industrial level is still based on a trial-and-error approach. The main challenge is to determine the viscous behaviour of melts under extrusion-like conditions that require specific rheometers1. The 1D global model of twin-screw extrusion Ludovic©2 for the design of processing experiments has been restricted to simple formulations: maize and wheat starches and wheat flour3,4. Up to now, it has not been used to design food products. Hence, this work aims to test whether this model, implemented with an appropriate viscosity law, can be used as a computer-aided tool for predicting various properties of fibre-rich breakfast cereals extruded under various operating conditions.Various food models were selected: blends of wheat flour and wheat bran (bran content ≤26 wt%). A large data set was built from literature data, including foods properties and extrusion variables (temperature T and specific mechanical energy SME)5,6,7. The foods characteristics were hydro-solubility of starch (WSIstarch), macrostructure described by radial expansion index (SEI) and cellular structure expressed as cell density per cm3 (NC). Twin-screw extrusion processing was simulated using the 1D global extrusion model Ludovic© (Sciences Computers Consultants, France). The extruder operating charts representing predicted extrusion variables as function of operating parameters were drawn. From the correlations between predicted extrusion variables (T, SME, melt viscosity η_com) and product features (WSIstarch, SEI, NC) (Fig. 1a), a set of extrusion variables to obtain a product with desired properties can be targeted. Thereafter, the feasible region of operating conditions can be determined from extruder operating charts (Fig. 1b). As a future prospect, extrusion ...