Characterization of Polyester Coatings Intended for Food Contact by Different Analytical Techniques and Migration Testing by LC-MSn

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.

Clearing Properties Between Coconut Oil and Xylene in Histological Tissue Processing

Xylene is the commonest clearing agent even though it is hazardous and costly. This study evaluated the clearing properties of coconut oil as an alternative cost-effective clearing agent for histological processes. Ten (10) prostate samples fixed in formalin were taken and each one was cut into 4 before randomly separating them into four groups (A, B, C and D). Tissues were subjected to ascending grades of alcohol for dehydration. Group A was cleared in xylene and Groups B, C, and D were cleared at varying times of 1hr 30mins, 3hrs, and 4hrs in coconut oil respectively before embedding, sectioning, and staining were carried out. Gross and histological features were compared. Results indicated a significant shrinkage in coconut oil-treated specimen compared with the xylene-treated specimen and only the tissues cleared in coconut oil for 4hrs were as rigid as the tissues cleared in xylene (p > 0.05). No significant difference was found in either of the sections when checked for cellular details and staining quality (p > 0.999). Coconut oil is an efficient substitute for xylene in prostate tissues with a minimum clearing time of 4hrs, as it is environmentally friendly and less expensive, but causes significant shrinkage to prostate tissue.

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.

A New Year's Message 2023

We wish you all happiness, health and progress in the new year [...].

Phthalate toxicity mechanisms: An update

Phthalates are one of the most widely used plasticizers in polymer products, and they are increasingly being exposed to people all over the world, generating health concerns. Phthalates are often used as excipients in controlled-release capsules and enteric coatings, and patients taking these drugs may be at risk. In both animals and human, phthalates are mainly responsible for testicular dysfunction, ovarian toxicity, reduction in steroidogenesis. In this regard, for a better understanding of the health concerns corresponding to phthalates and their metabolites, still more research is required. Significantly, multifarious forms of phthalates and their biomedical effects are need to be beneficial to investigate in the various tissues or organs. Based on these investigations, researchers can decipher their toxicity concerns and related mechanisms in the body after phthalate's exposure. This review summarizes the chemical interactions, mechanisms, and their biomedical applications of phthalates in animals and human.

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

Since the decline of the use of bisphenol A, the chemistry of the varnishes and coatings which are applied to the inner surfaces of metallic food contact materials is poorly documented. We hypothesised that can coatings are now diverse and bring forth various non-intentionally added substances (NIAS) to be described. Investigating complex components such as NIAS requires demanding non-targeted approaches. We investigated the coatings of 12 vegetable cans from the French market. More than 125 substances were pinpointed, among them 84 oligoester combinations from 8 diols and 4 diacids. Thus, oligoesters were the dominant family. Additives such as epoxidised soybean oil, bisphenol A diglycidyl ether and benzoguanamine derivatives and phenol-formaldehyde oligomers were also identified. A software for exploring databases of theoretical combinations of polyester and phenol-formaldehyde resin components (NIAS-db 1.0) was made available. The stepwise organic synthesis of native and deuterated combinations of neopentyl glycol and isophthalic acid (4 and 8 units, linear and cyclic) enabled a higher confidence level and monitoring in vegetable extracts. Migration of oligoesters averaged 330 µg/kg in the drained vegetables (43-1600 µg/kg). This study sheds light on the need to fulfil a proper risk assessment on this NIAS family (exposure and hazard characterisation).

Food and beverage can coatings: A review on chemical analysis, migration, and risk assessment

The internal surface of food and beverage cans is generally covered with polymeric coatings to preserve food and protect metal substrate from corrosion. Coating materials are complex formulations that contain different starting substances (e.g., monomers, prepolymers, additives, etc.) and in addition during the manufacture of the material several compounds can be formed (e.g., reaction products, degradation products, etc.). These substances have the potential to migrate into the food. Many of them have not been identified and only some have been toxicologically evaluated. This article aims to provide a comprehensive review on the analytical methods used for the identification of potential migrants in can coatings. The migration and exposure to chemicals migrating from can coatings are also reviewed and discussed so far, which is essential for risk assessment. Moreover, a brief section on the current status of the legislation on varnishes and coatings for food contact in Europe is also presented. Liquid chromatography coupled to diode array and fluorescence detectors and particularly to mass spectrometry and gas chromatography-tandem mass spectrometry seem to be the techniques of choice for the identification of potential migrants in can coatings. Some studies have reported migration levels of BPA (bisphenol A) and BADGE (bisphenol A diglycidyl ether) and derivatives exceeding the specific migration limits set in the European legislation. On the whole, low dietary exposure to migrants from can coatings has been reported. However, it is interesting to highlight that in these studies the combined exposure to multiple chemicals has not been considered.

Polymeric Coatings and Antimicrobial Peptides as Efficient Systems for Treating Implantable Medical Devices Associated-Infections

Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action and minimum environmental toxicity. One approach in infection control is based on the development of antimicrobial coatings based on polymers and antimicrobial peptides, also termed as “natural antibiotics”.