Modelling Passive Modified Atmosphere Packaging of Strawberries: Numerical Analysis and Model Validation

In modified atmosphere packaging (MAP) of horticultural produce, prediction of the evolution of gaseous O2 and CO2 concentrations inside packages is important to evaluate package performance and to reduce number of experimental trials needed to select packaging conditions. Mathematical modelling constitutes a useful tool in MAP design. A mathematical model for predicting oxygen (O2), carbon dioxide (CO2), and temperature (T) evolution inside MA packages of strawberries (Fragaria cv. San Andrea) during storage at constant temperature was developed. For model validation, experimental assays with strawberries packaged in passive atmosphere and stored at constant temperature were carried out. Gas transport and heat transfer within packages were modelled with traditional transport phenomena approach. Respiration modelling was performed by measuring strawberries’ respiration rate under different gaseous compositions via non-invasive O2 measurements. Model validation was achieved by comparing simulated O2 and CO2 concentrations and temperature evolution inside packages with experimental values obtained from 200 g strawberries packaged in polyethylene at a constant storage temperature of 19 °C for 70 hours. Temperature data loggers were inserted inside packages to measure temperature evolution. O2 and CO2 concentrations inside packages were determined every 6 hours using a food package analyzer. Implementation of model was done using COMSOL Multiphysics (release 3.4, COMSOL Inc., Burlington, MA). Model adequacy was checked by calculation of Root Mean Square Error (RMSE). Evolution of O2, CO2 and temperature in headspace throughout storage period was predicted by the model (RMSE< 2 for all variables), validating the multiphysics model proposed. The validated model can be used to test different package configurations to achieve adequate postharvest storage conditions for shelf – life extension of strawberries.