Determination of Rheological Behavior of Tomato Concentrates Using Back Extrusion

Abstract

ABSTRACTThe back extrusion testing technique can be a very useful tool in assessing the rheological behavior of non‐Newtonian fluids (e.g. tomato concentrates). In this procedure, an Instron Model 1122 Universal Testing Machine (with stainless steel, solid rod attachment) was used to measure the forces developed as diluted tomato paste was back extruded in a simple piston/annular cylinder geometry. Assuming power law behavior, the force‐distance data for extrusions at different piston velocities were analyzed to yield the dimensionless flow behavior index (n) and the consistency coefficient (k) for each sample. Back extrusion measurements were performed on hot break and cold break tomato concentrates with different % total solids. For comparison, rheological measurements were also done on a set of samples with a Carri‐Med Controlled Stress Rheometer.