As consumers seek more sustainable purchasing options for consuming and cooking their meals, there are a growing number of food contact materials made from novel mixtures and processes that incorporate natural materials. These can be items like reusable plastics with bamboo powder or single-use bowls made of compressed plant fibers. As more of these materials come onto the market it is important to regularly assess the safety of the materials and any concerns that should be raised for consideration when amending regulation.
In a review article published on January 24, 2023, in the journal Food Additives & Contaminants: Part A, Mu-Ying Guan from Jinan University, Guangzhou City, China, and co-authors focus on chemicals in food contact materials (FCMs) and articles (FCAs) containing or made from wood and bamboo. They described potential sources of intentionally (IAS) and non-intentionally added substances (NIAS), their migration into food and food simulants, and analytical methods used for the respective analysis.
Guan and co-authors summarized that most of the potentially hazardous chemicals detected in wood and bamboo containing FCAs are from melamine-formaldehyde-resins, paints and coatings (e.g., used as surface coverage of wood and bamboo articles), as well as preservatives and bleaching agents. Melamine and formaldehyde have been found to migrate from bamboo-containing plastic (FPF reported) which is of high concern (FPF reported and here). Paints and coatings would be problematic due to heavy metals. While IAS could be analyzed comparatively easy, it “has be proven to be more challenging for NIAS.” Guan et al. described that harsh use conditions of wood and bamboo FCAs would favor the generation of NIAS due to the structural damage of the compounds, for instance, the degradation of cellulose into 2-pentylfurtan. Furthermore, pesticides used to grow the resources for these materials could become problematic when still present in the final FCA.
Looking at current legislation the authors identified some shortcomings but think that “countries are gradually improving the laws and regulations for FCM/FCA, but there is still a lack of relevant research on bamboo and wood FCM/FCA, for example, more scientific evidence is strictly required to support safety assessment of those materials.” Three studies published in January and February 2023 were focusing on exactly that.
In an article published on January 28, 2023, in the Journal of Chromatography A, Magdalena Wrona from EINA-University of Zaragoza, Spain, and co-authors analyzed four types of ‘natural’ dishware, made from bamboo, palm leaf, wood, and wheat pulp, for non-volatile substances including NIAS.
Since the identification of NIAS is “highly challenging,” the scientists explored if ion mobility quadrupole time-of-flight mass spectrometry coupled to ultra-high pressure liquid chromatography (UPLC-IMS-MS) is suitable for this objective. They acquired the four dishes for food applications from a Spanish supplier and performed migration experiments in accordance with Regulation (EU) No 10/2011 using 10% ethanol, 50% ethanol, and 3% acetic acid as food simulants.
Wrona and co-authors identified 25 non-volatile compounds in total which “were mainly additives and food contact substances that are generally used to improve the properties of commercial dishes.” The researchers also quantified the levels of migration and reported that migration was highest from bamboo, followed by palm leaves, wood, and wheat pulp. Comparison with the specific migration limits (SMLs) set by Regulation (EU) No 10/2011 showed that most did not exceed their SML. However, in the bamboo dish three oligomers, cyclic diethylene glycol adipate, 3,6,9,16,19,22-hexaoxabicyclo[22.3.1]-octacosa-1(28),24,26- triene-2,10,15,23-tetrone, and 1,4,7,14,17,20-hexaoxacyclohexacosane-8,13,21,26-tetrone exceeded the SMLs. Concluding, the authors find “that manufacturing FCMs from natural materials does not guarantee food safety, since they may be manufactured with additives and are also susceptible to cross-contamination. It is recommended that tableware from different origins and of different brands should be studied and clear rules for these FCMs established.”
Researchers of the same group previously analyzed two dishes of wheat pulp and wood and detected 67 compounds in the migrates (FPF reported).
In an article published on February 2, 2023, in the Foods, Hong Zhang from Beijing Technology and Business University, China, and co-authors characterized non-volatile substances present in six food contact bowls/cups made out of plant fiber and plastic. The composites’ plant fibers were either bamboo or rice husk (three samples each) while the plastic component was polypropylene (PP), polylactic acid (PLA), or melamine formaldehyde resins (MF). After cryo-milling the samples they extracted the chemicals with ethanol, isooctane, and 4% acetic acid. The chemicals present in the extracts were determined by UPLC- quadrupole time-of-flight- (QTOF)/MS and spectra compared to NIST 20 as well as home-made MS/MS spectral libraries.
With their approach, the scientists tentatively identified 115 substances over the six products. In the two MF-based samples they detected melamine and some of its derivates (methylolmelamine, dimethylolmelamine, and two new melamine derivates) while in the PLA-based products, a large number of linear and cyclic PLA oligomers or their derivates were found to be present. In the PLA-based sample, numerous polybutylene adipate terephthalate (PBAT) oligomers were also identified which the authors explain by the fact that PBAT is often added to PLA to improve its mechanical properties. Additionally, “plant components, plasticizers, and surfactants used for polymer production were identified.
For instance the researchers tentatively identified bisphenol S (BPS, CAS 80-09-1) in all samples “through its origin remains to be further explored” and isoprothiolane (CAS 50512-35-1) in the products with rice husk which is used as an insecticide and fungicide to control rice pests. Applying the threshold of toxicological concern (TTC) approach, Zhang and co-authors reported that more than 50 of the detected compounds were Cramer class III substances. They concluded that more research is needed to elucidate the safety of plant fiber/plastic composites, “for example, the quantification and risk assessment of these oligomers, considering that most of them have no reference standards commercially available.”
One of the main components of wood and bamboo is cellulose. In an article published on January 19, 2023, in the Journal of Consumer Protection and Food Safety, Leda Coltro from the Institute of Food Technology, Campinas, São Paulo, Brazil, and co-authors investigated seven dry foods packaged in cellulose for the presences of phthalates and 2,6-diisopropylnaphthalene (DIPN). The scientists bought wheat flour, powdered chocolate, cornstarch, toast, and biscuits of which either the primary or secondary (outer) packaging was made of cellulose in retailers in São Paulo between 2016 and 2019. They extracted the food samples with dichloromethane and analyzed them for dibutyl phthalate (DBP, CAS 84-74-2), diisobutyl phthalate (DIBP, CAS 84-69-5), bis(2-ethylhexyl) phthalate (DEHP, CAS 117-81-7), and DIPN (CAS 24157-81-1) using gas chromatography – mass spectrometry (GC-MS).
Coltro and co-authors reported that five of the seven samples contained all targeted substances, while the remaining two contained at least one of the analyzed phthalates. The compound detected in the highest concentrations was DEHP with 1.56 to 3.85 mg/kg, followed by DIBP with 0.36 to 1.51 mg/kg. The values were 2.5 to 5 times higher than their SMLs as of the food packaging regulation in Latin America (Mercosur) which are 1.5 mg/kg for DEHP, 0.3 mg/kg for DBP (or their sum) while DIBP must be non-detectable (FPF reported and here). This “indicate[s] that better control is required in production processes in Brazil and more stringent good manufacturing practices to avoid food contamination and consumer exposures.”
In 2020, the European Commission’s Working Group concluded that bamboo-based additives are not authorized per se for use in plastic FCMs in the EU (FPF reported). One year later the EC and EU Member States agreed to launch an EU Enforcement Action Plan on bamboo powder-containing plastic FCMs to ensure that bamboo and other illegal plant-based additives are not marketed in the EU (FPF reported). As a result of the Action Plan, 21 European countries notified 748 cases of plastic FCMs containing ground bamboo in November 2022 (FPF reported). Since the end of 2022, a new bamboo and wood standard became effective in China which defines migration limits and testing protocols for substances in the FCMs (FPF reported).
References
Coltro, L. et al. (2023). “Occurrence of phthalates and 2,6-diisopropylnaphthalene in dry foods packed in cellulosic materials.” Journal of Consumer Protection and Food Safety. DOI: 10.1007/s00003-022-01412-x
Guan, M.-Y. et al. (2023). “Chemical contaminants from food contact materials and articles made from or containing wood and bamboo – a review.” Food Additives & Contaminants: Part A. DOI: 10.1080/19440049.2023.2167003
Wrona, M. et al. (2023). “Ultra-high performance liquid chromatography coupled to ion mobility quadrupole time-of-flight mass spectrometry for the identification of non-volatile compounds migrating from ‘natural’ dishes.” Journal of Chromatography A. DOI: 10.1016/j.chroma.2023.463836
Zhang, H. et al. (2022). “Elucidation of Non-Intentionally Added Substances from Plant Fiber/Plastic Composites by UPLC-QTOF/MS.” Foods. DOI: 10.3390/foods12030678
