PLA thermoformed trays incorporated with cinnamaldehyde and carvacrol as active biodegradable bakery packaging

Poly(lactic acid) (PLA) with enhanced antimicrobial functions can be used as sustainable food packaging to control microbial growth and reduce waste. PLA trays containing carvacrol (CAR) and cinnamaldehyde (CIN) as natural antimicrobial essential oils (EOs) were developed by cast sheet extrusion and thermoforming. Infrared spectra indicated interaction between CAR and CIN with PLA, involving the C--O bond in carbonyl and the C-H bond in methyl groups of PLA molecules. Incorporation of CAR and CIN produced clear PLA trays with modified X-ray diffraction angles of amorphous PLA structures. Shrinkage of the trays occurred at high EO levels, reducing tray depth. Adding both CAR and CIN reduced tray mechanical strength due to plasticization and water vapor permeability but increased oxygen permeability, suggesting the major effect of hydrophilicity-hydrophobicity on permeability. PLA with CAR (5 % and 8 %) had superior antimicrobial capacity against Escherichia coli than PLA/ CIN, while trays containing both EOs effectively delayed mold growth as active cake packaging, with CAR showing higher mold inhibition. Accordingly, EO types and concentrations controls mechanical strength, barrier properties and shrinkage of thermoformed PLA trays, while enhancing microbial controls in bakery products.