Modelling flow behaviour of dairy foams through a nozzle

Aerated materials are interesting systems widely used in many food applications; nevertheless, their dynamic behaviour is still under study aiming to relate macroscopic and technological parameters to fundamental properties of liquid matrix and operating conditions. In this work a system, based on a pressurised dairy emulsion stored at low temperature in a can, was considered, aiming to model either the foam flow through the can nozzle or the gas cell growth in the liquid matrix under pressure release from the internal value to the atmospheric one.A pseudo-homogeneous approach was used to analyze the flow inside the nozzle, considering “effective” properties, related to the liquid matrix parameters and to the local foam density; the latter was evaluated by solving a heterogeneous system based on the expansion of a single bubble in a viscoelastic liquid. The model was solved by a finite element method and numerical results were in good agreement with some experimental data. The model was then used to simulate different process conditions and it revealed to be helpful in evaluating technological parameters as function of formulation and operating conditions, reducing experimental trials.