Lesser galangal (Alpinia officinarum Hance) essential oil incorporated biodegradable PLA/PBS films as shelf-life extension packaging of cooked rice

Abstract

Adding natural essential oils to biodegradable polymers produces functional active packaging that reduces food loss and package waste. Polylactic acid and polybutylene succinate (PLA/PBS) films were produced via cast extrusion and blended with lesser galangal (Alpinia officinarum Hance.) essential oils (EO) at up to 6 %. Effects of EO and PLA/PBS ratios on morphology, relaxation, crystallinity and film properties were investigated. Results indicated that plasticization effects of EO reduced α-relaxation temperature and crystallinity, decreasing tensile strength by up to 22 %, while permeability of water vapor and oxygen increased by up to 42 % and 29 %, respectively. Interaction between EO and PLA/PBS shifted the diffraction angle, suggesting modified crystal morphology. EO enhanced melting of PBS giving smoother microstructures and reduced aggregates in the film matrices, contributing to lower surface roughness and hydrophobicity. Films were placed into packages of freshly steamed glutinous rice, allowing release of volatile lesser galangal EO majorly consisted of β-ocimene, 2-bornanone, eucalyptol and geraniol as determined by GC/MS. PLA/PBS films with lower PLA contents containing EO showed higher efficacy to delay fungal growth in cooked glutinous rice. Total microbial viable counts were significantly lower in packages containing EO above 4 %. PLA/PBS/EO films effectively extended the shelf-life of cooked glutinous rice by more than 2-fold depending on EO concentrations and PLA/PBS ratios due to release of volatiles into the headspace. Essential oil release from film interface into vapor and liquid phases showed antimicrobial functions which delayed mold and bacterial growth.