International Journal zyxwvuts of zyxwvutsrq Food Science and Technology zyxwvu (1990) 25,318-327 zyxw Diffusion of carbon dioxide in tomato fruits during cold storage in modified atmosphere N. BERTOLA, A. CHAVES zyxwv & N. E. ZARITZKY*, Universidad Nacional de La Plata, La Plata, Argentina zyxw Summary Treatments with 20% C02 of tomato fruit produced a beneficial extension of storage life. The diffusion of CO;! in tomato (Lycopersicon esculenturn Mill) cv. Platense was measured chromatographically and the concentration profiles in the internal gaseous atmosphere of the fruit were determined for non-steady state conditions to establish minimum treatment times that can ensure adequate penetration of the gas. The effective diffusivity of C02 in the tissue was determined by fitting concentration data, obtained from experiments with whole fruit without skin, to the non-steady state solution of the diffusion equation, assuming negligible external mass transfer resist- ance. The diffusivity was modelled using Maxwell-Eucken expressions, taking account of the heterogeneous structure of the tissue. The resistance of the fruit skin was evaluated using whole fruits with the stem scar covered with paraffin and fitting experimental data to the solution in terms of mass Biot number; the specific resistance of the peel was some 200 times greater than that of the stem scar. Keywords C02 diffusion coefficient, diffusion modelling, effective diffusivities of skin flesh and stem scar, gas storage. Introduction Although ripening of tomatoes can be retarded by low temperatures (Salunkhe & Desai, 1984), storage under refrigeration can cause chilling injury and an increase of fungal contamination (Ryall & Lipton, 1983). The use of temperatures between 10 and 20°C with atmospheres rich in C02 and low O2 content have been reported by several authors (Saguy & Mannheim, 1975; Buescher, 1979; Geeson et al., 1985; Mugridge & Chaves, 1988). The exposure of mature green fruits to C02 concentrations of the order of 20% v/v for relatively short periods (3 days at 10°C) has been considered adequate to slow down the ripening process of tomatoes (Mugridge & Chaves, 1988). The study of gas diffusion in fruits is required to determine the optimum treatment and is therefore both of theoretical and of practical interest. Authors’ addresses: Centro de Investigacidn y Desarrollo en Criotecnologia de Alimentos (CIDCA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 116, (1900) La Plata, Argentina. *Correspondent.