Flow Properties of Tomato Concentrates: Effect of Serum Viscosity and Pulp Content

Abstract

ABSTRACT Shear rate‐shear stress data were obtained on tomato serum samples at 5.6, 10, 15, and 20° Brix, and on 28 concentrates prepared from the serum samples and containing different amounts of pulp: +30%, +20%, +10%, normal, −10%, −20%, and −30%. Serum samples were Newtonian fluids while concentrates were shear‐thinning non‐Newtonian fluids. Apparent viscosities of concentrates increased linearly with pulp content expressed as weight %, volume %, or the weight ratio of pulp to serum. Apparent viscosity of the concentrates (η 100 conc) was related to the viscosity of serum (η serum) and pulp content (P) by the expression: η 100 cone =η serum + A * P ** B. The contribution of pulp content to η 100 cone was much more than that of serum. η serum was well correlated with pectin content by the expression: η serum = A 1 + B 1 (Pectin) ** C 1 .