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

Abstract

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.

Oligomers from the Synthetic Polymers: Another Potential Iceberg of New Pollutants

“…Additionally, there are various classes of additives, which are more convenient for practical application, that can be polymeric or oligomeric, leading to the formation of what is known as “primary oligomers” . In polyethylene naphthalate (PEN) materials, the primary oligomer content constitutes 0.81% of the overall polymer weight, while PET materials can contain 1.2% of oligomers. , Research on the oligomers of polycondensation polymers has widely began , and that of polyhydrocarbons formed by polyaddition such as were also reported, such as polyethylene (PE), PP, and PS. , However, the mechanism underlying the gradual release of primary oligomers from pre-existing products remains poorly understood. Several polymer materials utilized in food packaging have been assessed for their oligomer release rates, which have been found to be influenced by factors such as the type of food, storage duration, and temperature …”

“…12 In polyethylene naphthalate (PEN) materials, the primary oligomer content constitutes 0.81% of the overall polymer weight, while PET materials can contain 1.2% of oligomers. 30,31 Research on the oligomers of polycondensation polymers has widely began 32,33 and that of polyhydrocarbons formed by polyaddition such as were also reported, such as polyethylene (PE), 34 PP, 21 and PS. 20,35 However, the mechanism underlying the gradual release of primary oligomers from pre-existing products remains poorly understood.…”

Durable Surface Modification of Low-Density Polyethylene/Nano-Silica Composite Films with Bacterial Antifouling and Liquid-Repelling Properties for Food Hygiene and Safety

“…The majority of food preservation films are manufactured using common polymeric raw materials, such as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, and polybutylene terephthalate [ 12 ]. Widely employed in the food industry, these materials play a crucial role in FCMs [ 13 ], acting as effective physical barriers against bacterial invasion [ 14 ] and contributing to the extension of shelf life [ 15 ], thereby maintaining product quality. The surfaces of FCMs acquire a high level of hygiene properties through various mechanisms.…”

Odd-Even Effect of Polyesters‘ Cyclic Oligomers and the Definition of Oligomers Based on Physicochemical Properties

“…Different types of PES can be found in the market as base materials for several FCM applications, with polyethylene terephthalate (PET) as the most relevant. This polymer has been used for years due to its advantageous technological properties and characteristics over other polymers, such as possessing generally low levels of migration and being an efficient functional barrier against organic molecules [1][2][3][4]. These properties make PET one of the most inert foodcontact polymers and the polymer of choice for applications such as water bottles [5].…”

“…Some oligomers can be used as additives in the production of plastic polymers, but the majority are considered as non-intentionally added substances (NIAS). They can be formed through the degradation of the polymers due to thermal effects during production or recycling, by degradation due to various thermo-mechanical processes and as byproducts of the polymeric synthesis [1,4,9,[11][12][13][14]. The use of irradiation energy during sterilization treatments of packed foods (gamma or beta radiation), as well as high pressure, UV-light or ozone, can also promote the formation of oligomers [15].…”