Development of polyvinyl alcohol based active inner coating reinforced with chlorogenic acid and functionalized layered clay for food packaging

Abstract

Food packaging is developing towards more environmentally friendly polymer matrix and superior active functions. In this study, polyvinyl alcohol (PVA) based active coating incorporating chlorogenic acid (CGA) and CGA functionalized layered clay (LDHs@CGA) was applied to construct polylactic acid (PLA) three-layer active films on fully biodegradable PLA base film. The results indicated that PVA based active coating using dual coating technology (LDHs@CGA/PVA + CGA/PVA) had no visible interface and a uniform thickness, ranging from 4 to 5 μm. When the amount of LDHs@CGA was 1 wt%, the release of CGA in the active intermediate layer (CGA/PVA coating) was limited due to the natural barrier of LDHs@CGA in the controlled release layer (LDHs@CGA/PVA coating), resulting in a decrease in active functions. When the amount of LDHs@CGA reached 3 wt%, the antioxidant (DPPH method), antibacterial (Escherichia coli), and UV absorption (at 335 nm) reached 85.6 %, 87.2 %, and 73.2 %, respectively. This was because in addition to CGA as the main active substance, sufficient amounts of LDHs@CGA can also serve as secondary active substance to supplement the release of CGA. Meanwhile, the addition of LDHs@CGA could significantly improve the gas barrier properties of PVA based active coating, and the barrier to oxygen was much higher than that to water vapor. This study proposes a method of constructing PLA three-layer active films by coating with PVA based active inner coating, which can more effectively and stably exert the active functions for food packaging applications.