Mathematical modelling of diffusion channel length to maintain steady-state oxygen concentration for controlled atmosphere storage of tomato

Abstract

In this study, potential of the air-diffusion channels to maintain the desired controlled atmosphere condition in the storage chambers was evaluated. The diffusion channels of different combination in length (60, 120, 180, 240 mm) and diameter (3, 6, 9, 12 mm) were installed in the storage chambers of 2 L capacity. Tomato samples (0.805 kg) were taken in the chambers and stored at 10°C. Oxygen concentration in the chambers was measured periodically until the end of storage period. The tomatoes were stored upto 40 days under the channel length of 180 mm and diameter of 9 mm with harvest-fresh appearance, better texture and colour. The experimental results showed that the oxygen concentration ranging from 7% to 15% was maintained depending on the channel length and its tendency was found directly proportional to the channel diameter and inversely related to the channel length. Simultaneously, respiration rate of tomato was determined by closed respiration system to facilitate working with diffusion channel model. A model was developed based on Fick’s first law of gas diffusion to predict the channel length. The model was fitted to the experimental data and channel lengths were calculated theoretically in the ranges between 30 and 320 mm. The predicted channel lengths maintained the oxygen con centration between 4% and 16% irrespective of the channel diameters. The predicted results were in accordance with the experimental results. The model was very useful in predicting the diffusion channel length and establishing the controlled atmosphere condition for storage of tomatoes.