Zinc migration and its effect on the functionality of a low density polyethylene-ZnO nanocomposite film

Abstract

The interest in incorporating ZnO nanoparticles (ZnO-NPs) into food contact materials is increasing due to its attractive functions such as ultraviolet (UV) blocking and antimicrobial activity. Despite their benefits, the stability and functionality of ZnO-NPs could be altered when they come into contact with foodstuff through migration. Hence, we investigated Zn migration and its effect on the functional properties of low density polyethylene (LDPE)-ZnO nanocomposite films. The migration of Zn from nanocomposite films into food simulants (distilled water, 4% acetic acid (w/v), 50% ethanol (v/v) and n-heptane) was conducted at 70 degrees C for 30 min according to the Korea standard and specifications for food utensils, containers and packages conditions. The presence of Zn in the food simulants was verified by inductively coupled plasma-optical emission spectrometry. Different concentrations of dissolved Zn were observed ranging from 0.006 to 3.416 mg L-1 (except for heptane) and the level of migrated Zn was found as a function of the ZnO-NPs content in the nanocomposite film. However, the highest amount of migrated Zn measured in this study was lower than the specific migration limit regulated by the European Commission. In addition, the UV light absorption and the antimicrobial activity of the LDPE-ZnO nanocomposite film were significantly affected by the dissolution of ZnO, particularly in acetic acid. Therefore, particular attention is requested to use when LDPE-ZnO nanocomposite films are used for food packaging, especially acidic food, because Zn can likely migrate, and thereby their UV blocking and antimicrobial functions could be no longer effective.