Fibre-like structure formation in fava bean protein based extrudates: effects of extrusion inputs and potential of outputs for process control

High moisture extrusion processing (HMEP) is a complex process in which product formulation and extrusion conditions play a key role in fibre-like structure formation. The aim of this work was to study the effect of process input parameters (formulation, liquid feed, and extrusion temperature) on the texture development of a high moisture extrudate (HME) based on fava bean protein concentrate (FBPC), combined with a different protein source (pea protein isolate - PPI) or an oil ingredient (extra virgin olive oil (EVOO)). The influence of extrusion outputs (melt temperature, pressure, and torque) on texture parameters and its potential to control the texturisation process was also investigated. Formulation (protein source and added oil) and moisture content had a significant effect on textural characteristics of HME, while a variation of barrel temperature of 10 °C (from 145 to 155 °C) was not sufficient to influence the final product texture. Addition of PPI to FBPC-based HME increased hardness and fibrousness of the product, while oil addition had a lubricating effect which difficulted the formation of fibre-like structures in the direction of the extrusion flow. Out of the studied extrusion outputs, torque was highly correlated with the HME textural characteristics, showing potential for inline control of the HMEP process.