Thorough investigation of non-volatile substances extractible from inner coatings of metallic cans and their occurrence in the canned vegetables

Bringing to light vinyl chloride oligomers, a class of polychlorinated alkanes differing from chlorinated paraffins

Polyvinyl chloride (PVC) is one of the most widely used polymers, which contrasts with the low amount of literature on the leaching of associated additives and in particular unintended oligomers, a class of non-intentionally added substances (NIAS). This study sheds light on the occurrence of vinyl chloride oligomers (VCOs) in a variety of PVC analytical standards (n = 4), PVC items employed for construction, medical or food contact applications (n = 14), as well as in foodstuffs and environmental matrices (n = 10). Samples were analysed by liquid chromatography coupled to high-resolution mass spectrometry hyphenated with chloride-enhanced electrospray ionisation. Series of saturated (0VCO), monounsaturated (1VCO), diunsaturated (2VCO) and triunsaturated (3VCO) VCOs were revealed. The dominant series remained 1VCOs of the general formula C2nH3nCln, accounting for ∼80 % of VCOs in PVC standards. A risk of signal overlap was found between 0VCOs of the general formula C2nH3n+1Cln+1 (accounting for ∼8 % in PVC standards) and polychlorinated alkanes making up chlorinated paraffins, given that they share the same chemical formulas. A methodology for discriminating between signals arising from VCOs and chlorinated paraffins has been proposed. VCOs were detected in 88 % of the samples analysed (other than standards), and in particular in some foodstuffs and environmental matrices, suggesting that VCOs have the capacity to leach out of PVC materials, and thus contaminate food and the environment. Overall, these results call for greater attention to be paid to vinyl chloride oligomers and raise the question of whether they pose a risk to living organisms.

Hazard assessment of fenozan, a released non-intentionally added substance from polyester-based can coating

Since the safety of new-generation polyester-based internal coatings regarding the migration of non-intentionally added substances (NIAS) is poorly documented, studies are needed to identify NIAS originating from these food-contact materials (FCM). The aim of this study was to identify volatile and semi-volatile NIAS from polyester-based coatings in order to assess their hazard and ensure consumers' safety with regard to exposure from canned food. Extraction and migration tests were carried out on a single polyester-coated tin plate (5 batches) using two solvents: acetonitrile and ethanol 95%, then FCM's extracts and migrates were analysed by GC-MS. An antioxidant degradation (hydrolysis) product, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid or fenozan (CAS RN: 20170-32-5), was identified and confirmed by reference standard in all migrates. To assess fenozan's toxicity, several in vitro bioassays, such as the Ames test (to assess point mutation), the micronucleus assay (to detect chromosomal aberrations), and the iodide uptake assay (to study one mode of action for thyroid disruption) were conducted. Fenozan was negative in the Ames test on three strains of S. typhimurium (TA98, TA100, and TA1535) and on one strain of E.coli (WP2), with and without metabolic activation system (S9 mix) using direct incorporation and pre-incubation methods. The in vitro micronucleus assay conducted on HepG2 cells also exhibited a negative response following a 4-hour treatment with the S9 mix, and a 48-hour treatment without the S9 mix. A weak inhibitory effect was obtained when testing fenozan in the iodide uptake assay using rat thyroid FRTL-5 cells. Significant inhibition started from 800 µM of fenozan, with a maximal inhibition of almost 47% at 1000 µM. The findings indicate that fenozan exhibits an anti-thyroid activity in vitro.

Bisphenol A and its analogues: from their occurrence in foodstuffs marketed in Europe to improved monitoring strategies-a review of published literature from 2018 to 2023

In this review article, the research works covering the analytical determination of bisphenol A (BPA) and its structural analogues published from 2018 to present (February 2024) were examined. The review offers an overview of the concentration levels of these xenoestrogens in food and beverages, and discusses concerns that these may possibly pose to the human health and scrutinises, from an analytical perspective, the main biomonitoring approaches that are applied. This comes as a natural evolution of a previous review that covered the same topic but in earlier years (up to 2017). As compared to the past, while the volume of published literature on this topic has not necessarily decreased, the research studies are now much more homogeneous in terms of their geographical origin, i.e., Southern Europe (mainly Italy and Spain). For this reason, an estimated daily intake of the European population could not be calculated at this time. In terms of the analytical approaches that were applied, 67% of the research groups exploited liquid chromatography (LC), with a detection that was prevalently (71%) afforded by mass spectrometry, with over one-fourth of the research teams using fluorescence (26%) and a minority (3%) detecting the analytes with diode array detection. One-third of the groups used gas chromatography (GC)-mass spectrometry achieving comparatively superior efficiency as compared to LC. Derivatisation was performed in 59% of the GC studies to afford more symmetrical signals and enhanced sensitivity. Although the contamination levels are well below the threshold set by governments, routinely biomonitoring is encouraged because of the possible accumulation of these contaminants in the human body and of their interplay with other xenoestrogens.

Synthesis and quantification of oligoesters migrating from starch-based food packaging materials

The term oligomer refers to structurally diverse compounds coming from incomplete polymerisation or polymer degradation. Their ability to migrate into foodstuffs along with recent studies about their bioavailability and toxicity have risen concerns about the scarcity of standards needed to perform thorough analytical and toxicological studies. In this work, migration extracts of three starch-based biopolymers films for the packaging of fruits and vegetables were analysed according to European legislation 10/2011. Oligoesters analysed by UPLC-MS(QTOF) were the main non-intentionally added substances (NIAS) identified in the food simulants. A stepwise synthesis approach was used to synthesise and isolate eleven cyclic and linear oligoester standards ranging from 2 to 8 monomers based on adipic acid, 1,4-butanediol, isophtalic acid and propylene glycol monomers. These standards were characterised by 1H and 13C NMR as well as high resolution mass spectrometry. An overall high purity of > 98 % was achieved as detected by UPLC-MS(Orbitrap). The standards were then used to unequivocally identify the oligoesters in the migration assay samples by comparing their UPLC-MS/MS spectra, and to semi-quantify or fully quantify these migrant oligoesters. The oligoester quantification results deemed safe only one out of the three biopolymer films according to their threshold of toxicological concern concept. The work herein described aims to contribute towards the oligomers knowledge gaps, opening the door for comprehensive toxicological risk and absorption, distribution, metabolism, excretion and toxicity (ADMET) studies.

Oligoester Identification in the Inner Coatings of Metallic Cans by High-Pressure Liquid Chromatography-Mass Spectrometry with Cone Voltage-Induced Fragmentation

The application of polyesters as food contact materials is an alternative to epoxy resin coatings, which can be a source of endocrine migrants. By using high-pressure liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS) with cone voltage-induced fragmentation in-source, a number of polyester-derived migrants were detected in the extracts of inner coatings of metallic cans. The polyester-derived migrants were detected in each inner coating of fish product-containing cans (5/5) and in one inner coating of meat product-containing can (1/5). They were not detected in the inner coatings of vegetable/fruit product-containing cans (10 samples). The respective detected parent and product ions enabled differentiation between cyclic and linear compounds, as well as unambiguous identification of diol and diacid units. Most of the detected compounds, cyclic and linear, were composed of neopentyl glycol as diol and two diacid comonomers, namely isophthalic acid and hexahydrophthalic acid. The other detected oligoesters were composed of neopentyl glycol or propylene glycol and adipic acid/isophthalic acid as comonomers. The compounds containing propylene glycol as diol were found to be exclusively linear cooligoesters. On the basis of abundances of [M+Na]+ ions, the relative contents of cyclic and linear oligoesters were evaluated.

Mass spectral characterisation of cyclic oligoesters in a biodegradable mulch film

RATIONALE

Plastic mulch film manages weed growth and moisture loss on the surface of cropping beds. The chemical components of such plastics include polymer(s), additives and non-intentionally added substances (NIASs). The unknown chemical nature and behaviours of these constituents require investigation due to their potential to add to the anthropogenic chemical burden in the agrifood system.

METHODS

Solvent extracts of a commercial 15% polylactic acid (PLA)/85% poly(butylene adipate-co-terephthalate) mulch film were investigated using gas chromatography-mass spectrometry (GC-MS) with electron ionisation to characterise the additive and NIAS components. The obscurity of some of the NIASs meant their identification was not readily achieved through routine MS library comparisons. As such, the identification of several polymer-derived compounds required interpretation of the MS data and re-application of the derived fragmentation patterns with reference to the wider literature. Unknowns were confirmed using commercially available compounds.

RESULTS

Unknown NIASs were identified as cyclic oligoesters comprised of the monomeric building blocks of the polymer system. Cyclic structures derived from the monomers of polybutylene adipate (PBA) and polybutylene terephthalate (PBT) fragmented through a primary pathway involving 1,5- and 1,3-H transfers at ester linkages. Characteristic ions at m/z 111, 129, 183 and 201 for PBA-derived cyclic oligoesters and m/z 104, 132, 149 and 221 for PBT-derived cyclic oligoesters were assigned in the mass spectra of unknowns. Cyclic oligoesters containing sebacate moieties were also identified, indicating the presence of polybutylene sebacate as an unexpected component of the mulch.

CONCLUSIONS

Systematic analyses of the sort reported here are valuable for providing alternative approaches for the identification of plastic-related chemicals. Open publication of MS spectral data is required to build a greater understanding of the mulch film chemical components contributing to the environmental chemical load introduced to agroecosystems.

Identification of non-volatile non-intentionally added substances from polyester food contact coatings and genotoxicity assessment of polyester coating's migrates

Can's polyester coatings are intended to replace epoxy-phenolic ones due to rising safety concern regarding the potential release of bisphenol A under increased regulations and consumer pressure. In this study, hazard linked to the migration of non-intentionally added substances from a single polyester-coated tin plate (5 batches) to canned food has been studied. Migration tests were performed using acetonitrile (ACN) and ethanol (EtOH) 95 %. Non-targeted analyses by liquid chromatography-high-resolution mass spectrometry revealed the presence of four cyclic oligoesters classified as Cramer class III substances with an estimated exposure (calculated for French population only) below the threshold of toxicological concern value of 1.5 μg/kg b.w./day, suggesting a no safety concern. Moreover, migrates were tested using in vitro genotoxicity DNA damage response (DDR) test and mini mutagenicity test (MMT) with different strains of S. Typhimurium using direct incorporation (TA100, TA98, TA102, TA1537) and pre-incubation (TA100, TA98) methods. Samples were negative in both bioassays suggesting the absence of genotoxicity/mutagenicity of the mixtures. To verify any false negative response due to matrix effect, migrates were spiked with corresponding positive controls in parallel with the MMT and the DDR test. No matrix effect was observed in these experimental conditions.

Identification of potential migrants from epoxy and organosol coatings used in metal food cans

The coatings of metal cans may release complex mixtures of migrants into the contained foods, including non-intentionally added substances (NIAS), such as reaction products. All migrating substances should be studied to demonstrate their safety. In this work, the characterisation of two epoxy and organosol coatings was performed using several techniques. Firstly, the type of coating was identified using FTIR-ATR. Screening techniques based on purge and trap (P&T) and solid-phase microextraction (SPME) coupled to GC-MS were used to investigate volatiles from coatings. For the identification of semi-volatile compounds, an appropriate extraction was performed before analysis by GC-MS. The most abundant substances were compounds with at least one benzene ring and an aldehyde or alcohol group in their structures. Furthermore, a method to quantify some of the identified volatiles was explored. Secondly, HPLC with fluorescence detection (HPLC-FLD) was used to determine non-volatile compounds such as bisphenol analogues and bisphenol A diglycidyl ethers (BADGEs), with subsequent confirmation by LC-MS/MS. Additionally, migration assays were performed by this technique to determine non-volatile compounds migrating into food simulants. Bisphenol A (BPA) and all BADGE derivatives except BADGE.HCl were detected in the migration extracts. Moreover, BADGE-solvent complexes such as BADGE.H₂O.BuEtOH, BADGE.2BuEtOH, etc. were also tentatively identified using the accurate mass provided by time-of-flight mass spectrometry (TOF-MS).

Poly(ethylene terephthalate), Poly(butylene terephthalate), and Polystyrene Oligomers: Occurrence and Analysis in Food Contact Materials and Food

Polyesters (PES) and polystyrene (PS) are among the most used plastics in the production of food contact materials (FCM). The existence of compounds that could migrate from these materials into food requires a constant analytical control to ensure the safety of consumers due to consumption. It also implies a significant research challenge for their identification and quantification. One of the most important groups of known FCM migrants are the substances known as oligomers. PES and PS oligomers have long been suspected to possess some toxicological effects. The International Agency for Research on Cancer and the European Food Safety Authority alerted recently to the potential carcinogenicity of styrene, with its oligomers consequently being also in the spotlight. At the same time, PES cyclic oligomers are categorized as having Cramer III toxicity. Many recent works on the occurrence of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and PS oligomers in FCM and food have been published. The oligomeric chemical analysis requires the use of demanding analytical strategies to address their different physicochemical characteristics (melting points, octanol/water partition coefficients, and solubility properties). Chromatographic methods are normally preferred due to the intrinsic complexity of the target matrices, but the reduced amount of reliable analytical standards still hinders the widespread screening analysis of oligomers in food. This work presents the most relevant recent studies and analytical methodologies used in the analysis of PET, PBT, and PS oligomers in food and FCM, as well as current and future challenges.