Assessment of ultrasonic treatment on multilayer packaging composed of polyethylene and ethylene-vinyl alcohol copolymer

Abstract

While there is an increase in the non-conventional processing of foods, the impact of emerging technologies on packaging materials is scarce, limiting their application. This work evaluated the ultrasound (US) technology, applied alone or in combination with thermal processing (thermosonication), on the structure, properties and functionality of PE/EVOH38/PE multilayer flexible packaging films. Samples were processed using US (25 kHz, 9.74 W/L) alone (25 ◦ C) or in combination with mild thermal processing (60 ◦ C) for up to 120 min. Packaging structure, properties and functionalities were evaluated through FTIR, DSC, XRD, SEM, mechanical and barrier properties, as well as overall migration. US treatment induced variations in relative crystallinity (XRD and DSC), but without changing the molecular or microscope structure (FTIR, SEM) of the films. As a consequence, the packaging functionality was not affected, preserving the mechanical properties (tensile test at both machine and transversal direction, and seal strength assay), water barrier (WVTR) and food-contact regulations (overall migration). As a consequence of the plasticizing effect of water on the EVOH layer, oxygen barrier (OTR) was increased, but keeping the barrier performance by remained within the expected range. Overall, the results indicate that the US-assisted treatment conditions here evaluated can be applied to PE/EVOH/PE multilayer packaging without compromising its performance.