Antifungal and plasticization effects of carvacrol in biodegradable poly(lactic acid) and poly(butylene adipate terephthalate) blend films for bakery packaging

Incorporation of essential oils in biodegradable polymers produces functional sustainable packaging materials that can extend the shelf-life of foods through enhanced antimicrobial capacity. Carvacrol was incorporated in poly(lactic acid) (PLA) and poly(butylene adipate terephthalate) (PBAT) blends at different polymer proportions (30–70%) by extrusion film blowing. Biodegradable films were characterized for morphology, thermal transition and mechanical and barrier properties. Stronger mechanical relaxation in PLA indicated plasticization effects of carvacrol, giving reduced relaxation temperature with enhanced exposure of PLA as a dispersed phase in PBAT matrices and improved compatibility. Polymer-polymer and polymer-carvacrol interactions involving C=O carbonyl bonds contributed to more homogeneous microstructures. Carvacrol plasticized films had dense matrices with increased crystalline fraction of PLA that reduced permeation of vapor and oxygen. Release rates of volatile carvacrol were enhanced in lower PLA matrices, while films showed delayed fungal growth and sporulation of Penicillium sp. and Rhizopus sp., with 2.0–2.3 times increased shelf-life of packaged bread and butter cake. Films containing plasticized carvacrol showed enhanced antifungal capacity, while PLA/PBAT blend ratios controlled the strength, permeability and release behavior of carvacrol.