Supplementary information : Functionalizing Calendered PLA/PBAT Films with Natural Food Additives

Herein, biodegradable and functional films based on PLA/PBAT (Ecovio^®) blends were prepared by calandering processing that allows high-quality films and proper blend mixing. To provide functional properties such as antioxidant and antimicrobial activity, food additives were incorporated including sodium stearoyl lactylate (designated as E481) at 5 wt% and bioplasticizers derived from vegetable oils, namely CITREM (E472C) and ACETEM (E472A) at 10 wt%. Chitin nanocrystals were also added to enhance barrier and mechanical properties. The films of around 200 μm thick were produced resulting in uniform and high-quality materials. Scanning electron microscopy and confocal Raman microscopy demonstrated good mixing of PLA and PBAT biopolymers, as well as a homogeneous dispersion of the additives. This effective blending provides excellent mechanical performance, particularly elongation at break, with values approaching 500% for most of the prepared films. The additives had minimal effect on the crystallinity, thermal and barrier properties while imparting antioxidant and antimicrobial properties with negligible migration into food simulant media, bellow 0.08 mg/Kg in all the cases. Citroglycerides, mono-and diglycerides of fatty acids and sodium stearoyl lactylate provides Trolox equivalent antioxidant capacity (TEAC) values between 14 and 18 µmol Trolox/g, and were effective against Gram-positive Staphylococcus aureus and Listeria innocua achieving complete bacterial inhibition at the contact tested concentration (ΔLog CFU/mL: 4.54 and 3.71, respectively). Finally, the disintegration of the films under industrial composting condition was demonstrated; this issue is essential to evaluate the environmental impact of the packaging at the end of its life cycle.