An article published on November 2, 2018, in the peer-reviewed Journal of Chromatography A, reported on the “determination of non-volatile components of a biodegradable food packaging material based on polyester and polylactic acid (PLA)” and their migration to food simulants. Margarita Aznar and colleagues from the Analytical Chemistry Department, GUIA Group, University of Zaragoza, Spain, analyzed pellets and films made of a “blend of PLA and a biodegradable fossil-based polyester,” provided by an unrevealed “packaging company.”
The scientists first optimized a novel dissolution/precipitation methodology with “dichloromethane/ethanol used as solvent/antisolvent system” to perform representative extractions of pellets and films. The non-volatile substances in the extracts were then analyzed by a mass spectrometry-based method. Further, non-volatile substances were studied in the migrates obtained by total immersion of film samples in three different food simulants, 10% and 95% ethanol as well as 3% acetic acid.
In total, 37 compounds were detected in all the experiments in total. Among these, 23 compounds were detected in pellet samples. In the extracts of film samples, only 19 out of these 23 compounds could be detected, and “no new compounds” were observed. Thus, “the extrusion process from pellets to film did not generate any new compound but some of them disappeared,” the authors concluded. In the film migrates, only 14 out of the 19 compounds seen in film extracts could be detected. However, 14 new compounds, mostly linear PLA oligomers, were observed. These substances were “probably generated from the reaction between the components of the packaging material and the simulants.”
Four cyclic oligomers “coming from the polyester part of the blend” had the highest intensity in pellet extracts as well as in all subsequent experiments, implying “that the polyester part of the blend had a critical role in the risk assessment of this kind of materials.” These oligomers were composed of adipic acid (CAS 124-04-9), phthalic acid (CAS 88-99-3), and butanediol (CAS 513-85-9).
Among the compounds detected in pellets with “medium intensity,” the scientists highlighted “PLA cyclic oligomers” composed of lactic acid (CAS 50-21-5), two “plasticizers with adipate structure,” a glycol “probably used as PLA plasticizer” and a “compound with piperidine structure . . . probably used as light stabilizer.” The cyclic oligomers were also detected in film extracts but not in the migrates, “probably because they reacted with food simulants, inducing a cycle opening and formation of new compounds,” i.e. linear oligomers.
The compounds detected with “the lowest intensities” included “some plasticizers, PLA oligomers and compounds defined as indirect additives to food contact materials by the U.S. Food and Drug Administration.”
The authors conclude that “in addition to the screening in the [extracts of] film samples, a screening study in the migration solutions is necessary in order to have a comprehensive information about the migrants present in the food simulants.” They further inform that “a future quantification of the compounds detected would also establishing a correct risk assessment of the material.”
Reference
Aznar, M., et al. (2018). “Determination of non-volatile components of a biodegradable food packaging material based on polyester and polylactic acid (PLA) and its migration to food simulants.” Journal of Chromatography A (published November 2, 2018).
