From macroscopic to molecular scale investigations of mass transfer of small molecules through edible packaging applied at interfaces of multiphase food products

This paper presents a multi-scale approach to investigate mass transfer properties of edible films that integrates some published data and new original results. The transport of small molecules, such as water, between the different parts of multiphase food products leads to quality deterioration and thus requires the use of barrier edible films or coatings. Therefore, it is necessary to characterise the properties of both food and edible barriers, like the diffusivities of their respective migrants. Surface properties characterisation of edible films, composed of an iota-carrageenan matrix in association with a high melting point fat was investigated by goniometry and allows the determination of wetting and water absorption, with emphasis on the constituents functionality. Diffusion of a model probe using the FRAP (Fluorescence Recovery After Photobleaching) method is characterised by a critical water content threshold, inducing an increase of the molecular mobility, and better explains the role of glycerol, used as the plasticizer. This study brings information on the diffusion of a small molecule in the film. Further NMR (Nuclear Magnetic Resonance) spectroscopy investigation contributes to a better understanding and identification of the interactions between the polymer and the diffusant. Finally, FTIR-ATR (Fourier Transform InfraRed–Attenuated Total Reflectance) analysis enables to obtain the diffusion coefficient of the liquid water in the film. Such a multi-scale investigation highlights the permeation mechanism within edible barriers.Industrial relevanceSynthetic food packaging is usually used to prevent mass transfers of some molecules, such as moisture, gases, flavor compounds or solutes, between a food and its surrounding medium. In the case of multiphase food products, the development of edible films and coatings, applied between the different phases of this food, has a great potential to increase its shelf life. This article examines the different scale levels of investigation in order to determine the diffusivity of small molecules through these edible packaging.