The objective of this study is to develop a methodology based on flow visualisation in order to measure the cumulative distribution of particles in vertical and horizontal tubes and to validate it with model and real food suspensions. The cumulative particle concentration provides new information in addition to the description of suspension flow, the residence time distribution, as well as the particle to fluid relative velocity and the friction curves. The method proposed firstly enables us to draw up a geometrical description based on a theoretical analysis of the suspension (homogeneous suspension, stationary bed) and secondly, to define the quantitative criteria issuing from the cumulative particle distribution. The cumulative distribution was investigated with a model suspension (alginate beads in CMC solution) and a real industrial product (bean mixture) versus flow-rate (from 233 up to 29221 h(-1)), concentration (from 3% up to 26% w/w) and particle-to-pipe diameter ratios (from 0.187 up to 0.330). Strong analogies between model and real suspension behaviour were noted when the particle concentration increases. However noticeable differences were observed and the results show that the flow pattern depends on four major parameters: (i) the orientation of the tubes and (ii) the density differences (and associated dispersion) between the carrier fluid and the particles; but (iii) the shape and (iv) the mechanical properties of particles are factors which limit particle concentration increase and cause fluids to tend toward homogeneity. (c) 2005 Elsevier Ltd. All rights reserved.