Antimicrobial biodegradable blown films from PBAT/TPS with Glucono-delta-lactone as acid regulator active packaging

Abstract

Glucono-delta-lactone (GDL), an acid regulator commonly used in food preservation, was incorporated into biodegradable poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS) (60/40 and 70/30) blended films to evaluate its antimicrobial activity and its influence on film properties. The blends were characterized for chemical interactions, morphology, thermal, mechanical, and barrier properties. Antimicrobial activity against Staphylococcus aureus and Escherichia coli was also assessed. FTIR analysis revealed interactions between GDL and starch at the -OH regions, resulting in a decrease in melting temperature. Microstructural observations showed a fibrous structure and increased compaction in PBAT/TPS films with GDL incorporation. Thermal analysis indicated that GDL modified thermal properties, possibly due to its promotion of higher crystallinity in the blended films. The addition of GDL also improved mechanical strength in both blending ratios, potentially through cross-linking. However, excessive GDL use weakened mechanical properties, likely due to acid-induced polymer hydrolysis. GDL increased the water contact angle in both blending ratios, suggesting enhanced surface hydrophobicity. The introduction of GDL into the blended films improved barrier properties, especially oxygen barrier. Additionally, GDL's antimicrobial properties effectively limited the growth of S. aureus and E. coli, particularly in high-moisture environments. Therefore, biodegradable PBAT/TPS films incorporating GDL demonstrate potential as active packaging materials. A 2 wt% addition of GDL was found to offer optimal performance in terms of film properties and significantly influenced the chemical, morphological, and thermal properties of the PBAT/TPS biodegradable packaging.