Synergistic enhancement of functional properties in EGCG and ferulic acid incorporated konjac glucomannan/gelatin bilayer films for blueberry preservation

Abstract

The rapid deterioration of perishable foods poses significant challenges to storage and distribution, highlighting the urgent need for innovative packaging solutions with antioxidant and antibacterial properties. In this study, we developed a novel double-layer active film composed of konjac glucomannan (KGM) and gelatin (Gel), incorporating epigallocatechin gallate (EGCG) and ferulic acid (FA) as functional agents. The film layers were fabricated by casting, and hydrogen bonding occurred between the active substances and both components of the biopolymer matrix-KGM and gelatin, which collectively enhanced the film's structural stability. To address the requirement for mechanical robustness, the K/G (e1:f1) film (with a 1:1 inner-to-outer ratio of EGCG to FA) achieved a tensile strength of 89.13 MPa and an elongation at break of 23.64 %. For barrier performance against moisture and oxygen, the film exhibited low water vapor permeability (1.18 × 10⁻¹⁰ g/Pa·s·m) and oxygen permeability (1.64 × 10⁻⁸ g/Pa·s·m), with nearly 100 % UV blocking efficiency. Regarding antioxidant capacity, films with higher EGCG or FA content (ratios of 2:1 or 1:2) demonstrated DPPH and ABTS free radical scavenging rates exceeding 94 %. The K/G (f2:e1) film also achieved almost complete inhibition (>99 %) of Escherichia coli and Staphylococcus aureus, meeting antibacterial requirements. Furthermore, the film exhibited a sustained release behavior fitting a first-order kinetic model (R² > 0.90), effectively extending the shelf life of blueberries by up to 9 days. Importantly, the film was fully biodegradable within 15 days under natural conditions. Overall, the developed KGM/Gel double-layer films offer a promising strategy for active food packaging by integrating antioxidant, antibacterial, slow-release, and environmental sustainability features.