In an article published on December 7, 2021, in the peer-reviewed journal Food Chemistry, Elena Canellas and co-authors from the University of Zaragoza, Spain, reported on the migration of non-intentionally added substances (NIAS), including oligomers, from biodegradable teacups. The scientists purchased a multilayer teacup which is, according to the manufacturer, 100% compostable and biodegradable being made of 40% polyester, 60% polylactic acid (PLA), as well as biodegradable adhesives and paper. Migration experiments were performed with the biodegradable polymer in contact with hot (100 °C) or cold (20 °C) tea. Samples were applied to liquid chromatography coupled to ion mobility time-of-flight mass spectrometry (UPLC–IMS-Q/TOF) and gas chromatography-mass spectrometry (HS-SPME–GC–MS) for the non-target analysis of non-volatile and volatile compounds, respectively.
Canellas et al. detected seven non-volatile compounds, including benzisothiazolone (CAS 2634-33-5) and the flame retardant and plasticizer tributyl phosphate (CAS 126-73-8) whose identity could be confirmed with corresponding standards, as well as five cyclic oligomers for which no commercial standards are available. One additional non-intentionally added oligomer belonging to the same family as the non-volatile oligomers was identified by HS-SPME–GC–MS and spectrum comparison with NIST 2014 library. Since for the identified NIAS no specific migration limits (SML) exist, the authors applied the threshold of toxicological concern (TTC) approach to calculated SMLs. The migration of benzisothiazolone and tributyl phosphate in hot tea was below their SML, and the migration of non-volatile cyclic oligomers (2.56 – 4.60 mg/kg) was reported to exceed the SML established by European regulations for Cramer class I substances. The researchers further found that “the migration to cold tea was an order of magnitude lower” than to hot tea. Canellas and co-authors concluded that their “work highlights the significance of the detection and identification of NIAS in food migration extracts, which should be performed on new and novel biodegradable as well as conventional materials.”
Scientists from the same research group have previously tested different techniques for oligomer detection and reported that polyester oligomers migrate from biopolymers (FPF reported).
In an article published on December 8, 2021, in the journal Food Research International, Antonella Cavazza and colleagues from Universit`a degli Studi di Parma, Italy, also investigated oligomer migration but from reusable food contact materials (FCMs) made of polycarbonate (PC). The authors laid out that current European regulation restricts the use of bisphenol A (BPA; CAS 80-05-7) in FCMs only by quantifying BPA migration from new products and, thus, is disregarding BPA originating from hydrolysis of unreacted oligomers or oligomers derived from material degradation during a product’s life-cycle. To analyze this “hidden source” of BPA, the scientists performed migration experiments with 36 PC tableware products in food simulant (ethanol 95%) and food (dark chocolate). Using liquid chromatography coupled to mass spectrometry (UHPLC-HRMS) followed by mass spectrum fragmentation analysis, Cavazza et al. found “oligomers, dimer, trimer, and tetramers, plus species deriving from uncomplete polymerization process […] migrate from PC items to simulant and chocolate.” Already after 15 min at 40 °C, oligomers were detected in food. Besides the kinetics of oligomer release, the study further investigated how product age, usage time, and the number of washing cycles affects substance migration. The authors highlight “that the presence of oligomers of polycarbonate deriving [from] unreacted species or polymer degradation (belonging to NIAS) can be considered a hidden source of several BPA units that remains outside the control of legislation and should be considered of high concern.”
Canellas, E. (2021). “The detection and elucidation of oligomers migrating from biodegradable multilayer teacups using liquid chromatography coupled to ion mobility time-of-flight mass spectrometry and gas chromatography–mass spectrometry.” Food Chemistry. DOI: 10.1016/j.foodchem.2021.131777
Cavazza, A. (2021). “Oligomers: Hidden sources of bisphenol A from reusable food contact materials.” Food Research International. DOI: 10.1016/j.foodres.2020.109959