STRUCTURAL PROPERTIES AND MECHANICAL DURABILITY OF EXTRUDED FISH FEED

摘要

This article investigates the possible correlation between mechanical properties ofrnfish feed pellets and their mechanical durability. Mechanical properties werernobtained by texture profile analysis (TPA) and stress relaxation test (SRT) of differentrntypes of fish feed. The results were correlated against a conventional test ofrnmechanical durability (DORIS, Durability On a Realistic, test). From SRT it wasrnfound that for achieving a high durability, pellets should be able to relax anrnapplied force nonelastically. From TPA, it was found that a durable pellet shouldrnalso be able to return its original state after a deformation. By fitting SRT datarnwith a two time constant generalized Maxwell model, it was found that the largestrntime constant is ∼7 s. The waiting time in-between the two impacts in TPA wasrnincreased from 5 to 15 s, which significantly improved the correlations againstrnmechanical durability.