A mean-field phase separation model enabling the coupling of non-isothermal flow phenomena with fibre formation in high-moisture extrusion of meat analogues

In this study, a coupled model integrating flow, temperature, phase separation, fibre alignment, and wall-slip has been developed to elucidate the complex behaviour observed during high moisture extrusion (HME) fibre formation. By departing from previous high-resolution approaches, the model uses a mean-field simplification to conveniently address wall-slip, thus avoiding the numerical intractability associated with resolving microscopic phases through solving the full Cahn-Hilliard equations. The critical simulation parameters are justified through prior studies and microscopy data and may to a certain extent be quantifiable from dead-stop experiments. The model can capture key qualitative features of HME, including the spatial distribution of fibres in the cooling die and their orientation, as observed in microscopy. Moreover, the model explains a potential delicate interplay between die cooling, phase separation/syneresis and protein melt flow characteristics. The study identifies extensional and pre-cooling die orientation of fibres as promising avenues for future model refinement. • The model enables coupling relevant non-isothermal flow phenomena with fibre formation in the cooling die during high moisture extrusion. • The impact of cooling temperature on plug flow transition is explained through a mean-field phase separation/syneresis dependent wall-slip condition. • A simple shear history-dependent fibre alignment measure is proposed that enables a composite measure of fibre formation. • Qualitative agreement between microscopy data and the location of predicted oriented and randomly oriented fibre domains in the extrudate is obtained. • The model offers a practical coarse-grained alternative to solving the Cahn-Hilliard equation for prediction of fibre formation.