Information on pore formation and their characteristics in foods during processing is needed for process design, in estimating other properties (i.e. thermal conductivity, moisture diffusivity), and characterizing the quality of a product. In this study the characteristics of pores in dried tuna (Thunnus tongol) processed by air-, vacuum-, and freeze-drying were measured by mercury porosimetry. Apparent, substance and true densities, porosity and pore size distributions of dried samples were measured to study the pores formed during the drying processes. The apparent density of fresh tuna flesh was 1098 kg/m, while the densities of dried tuna by air-, vacuum-, and freeze-drying were 960, 709 and 317 kg/M, respectively. Porosity of freeze-dried sample was much higher than those the air-dried and vacuum-dried samples. Pores in different samples were characterized as the total intruded volume, total surface area, pore size range and average diameter, and nature of the pore size distribution curves. Peroxide value and color of dried tuna meat were also measured. (C) 2002 Elsevier Science Ltd. All rights reserved.