Preconditioner influence on twin-screw extrusion cooking of starch-based feed pellets: The example of Fish Feed

This work compares the performance of pellets for adult Trout obtained in two different processing conditions. The first one consists of adopting the traditional Fish Feed process based on a preconditioning steam treatment step before twin-screw extrusion. The second one was a simplified process based only on a twin-extruder ensuring both the cooking and the extrusion of fish pellets in a single step. Six formulations were obtained while maintaining feed specifications (36 % of proteins and 30 % of lipids). The comparison between the two processing methodologies (i.e., with or without preconditioning) was then based on two fundamental aspects. Firstly, the gelatinization rate of starch contained inside pellets was determined. Secondly, the pellet’s characteristics (bulk density, expansion ratio, diameter and pellet’s porosity) and their usage properties (oil leakage rate, durability, hardness and floatability) were evaluated. The present work has evidenced that it is possible to produce pellets without preconditioning while ensuring a total starch gelatinization and maintaining their usage properties. The Fish Feed process has thus been partially simplified. •Twin-screw extrusion process is a versatile tool for aquafeed production.•Expansion phenomenon is crucial to optimize Fish Feed pellets physical properties.•Pellets with accurate usage properties can be obtained without preconditioning.•Fish Feed process thus becomes highly simplified.•Adequate moisture content is of critical importance to monitor pellets properties.