Modeling and simulation of an active packaging system with moisture adsorption for fresh produce. Application in ‘Hass’ avocado

Abstract

In an active packaging system, the control of moisture condensation can significantly reduce deterioration and loss of shelf life for fresh produce. In this study, an integrated mathematical model is proposed to represent the transport of water in an active packaging system with a moisture adsorber. For this, suitable equations were used to represent the different processes involved: a first-order kinetics and a Freundlich equilibrium equation were used to represent the adsorption from the active element. The product transpiration was represented by considering its heat of respiration and the difference in water concentration between the product and the packaging headspace surrounding it. Likewise, the differential equations of mass balance for O2, CO2, N2 and water vapor were established for the active packaging. For the moisture adsorption, a mixture of sodium polyacrylate (SPA) and cotton in ‘sachets’ of porous vegetable paper (70% SPA w/w) was used as adsorber determining its capacity and rate of adsorption as a function of relative humidity and temperature. To validate the proposed model, ‘Hass’ avocado samples were stored in rigid perforated polyethylene terephthalate (PET) packages for 12 days at 12 °C. With the model it was possible to satisfactorily represent the accumulation of moisture in the package, the amount of water adsorbed by the adsorber and the weight loss of the packaged avocado fruits (R2 = 0.97–0.99 for the different tests).