Two research studies and one review evaluated microplastics in food, looking at migration from food packaging, occurrence in food, methods to detect and identify them, as well as the public’s understanding of microplastics including potential sources and impacts.
In a review article published on August 8, 2022, in the journal Microplastics, Klytaimnistra Katsara and co-authors from different Greek universities and research institutes, summarized the literature on the migration of micro- and nanoplastics from plastic food packaging and the presence in food with a focus on honey.
The authors described that the migration of contaminants from food packaging into food is usually studied by using food simulants. Such experiments have demonstrated that chemicals as well as plastic monomers can migrate from the packaging into the food. Individual studies have used the same approach to show that microplastics migrate, e.g., polystyrene fragments into drink simulants or nylon and polyethylene terephthalate (PET) particles from tea bags into the tea itself. However, most studies on microplastics in food and beverages focused on their mere presence without experimentally demonstrating whether they originated from plastic packaging or other sources.
For honey, Katsara and co-authors summarized that besides chemicals such as styrene, plasticizers, and bisphenol A, large numbers of synthetic particles have been detected in honey, mostly studied under laboratory conditions. The particles would result from the harvesting, processing, and packaging of the honey although plastics “were already present in the honey bees’ feed, body, and wings, transferred to the hive from the blossoms.” Therefore they concluded that micro- and nanoplastic presence in honey has not yet been “directly connected to food packaging or the different types of honey and their properties (viscosity, pH value, and moisture content) or their storing conditions (temperature, humidity, light, and time).” The scientists emphasized that a standardized isolation, detection, and quantification method needs to be developed to study plastic particle migration into honey. Furthermore, they highlighted that the use of plastic packaging would need to be reduced and new packaging materials, more resistant to stress conditions, be developed “to eliminate the possibility of microplastic/nanoplastics migration” and to better protect human health.
Jinwoo Kim and co-authors from the Korea University, Seoul, South Korea, agree with Katsara et al. that the quantitative analysis of microplastics in foods is important since humans are exposed via that sources. In an article published on August 22, 2022, in the Journal of Food Composition and Analysis, they present a method to isolate, detect and identify microplastics in foods using the “three representative foods” salts, soy sauce, and pollock roe.
They reviewed existing sample pretreatment methods and selected six of which they compared digestion efficiencies by measuring the remaining total carbon. Based on their assessment, Kim and co-authors proposed a digestion method based on hydrogen peroxide (H2O2) for pretreating salt and soy sauce samples and one based on potassium hydroxide and H2O2 for the pollock roe. To test the robustness of their method (i.e., extraction recovery of reference materials), they spiked the three food types with reference materials including five polymer types, and sent the samples to four independent laboratories without providing them the types and numbers of the reference materials. After the pretreatment/extraction, the laboratories applied Fourier-transform infrared spectroscopy for microplastic analysis.
Kim et al. reported the average microplastic recovery rates were 73.2%, 76.9%, and 86.2%, for salt, soy sauce, and salted pollock roe, respectively. Furthermore, “analysis of variance of the experimental results demonstrated that the recoveries of the reference materials did not depend on any of the five plastic materials or the participating laboratories, indicating that the proposed methods are capable of reliably determining microplastics greater than 100 µm in selected foods.” Three of the laboratories also analyzed the microplastics present in the unspiked, packaged salt, soy sauce, and pollock roe samples. The number of detected particles differed between sample types and laboratories. Between 77 and 332 items were detected in 100 g salt, between 12 and 78 in 100 ml sauce, and between 25 and 39 particles in 10 g pollock roe.
The authors concluded that the food sample pretreatment method needs to be adapted according to the nature of the organic matter that might interfere with the particle analysis instead of using a universal method. Moreover, they highlighted that “although the isolation and identification methods for microplastics were found to be robust… it is still uncertain whether the selected methods are sufficient for smaller microplastics because the size of the reference materials used in this study was approximately 100 µm.” Since adverse effects are expected to increase with decreasing particle size, they recommended validating their method for smaller particles.
Marcos Felipe-Rodriguez and co-authors from the University of Bergen, Norway, explored the general public’s understanding of microplastics including occurrence (i.e., spread) and consequences. In their article, published on August 3, 2022, in the journal Frontiers in Psychology, they described how they surveyed 2720 adult Norwegians and analyzed their responses to open-ended questions. The survey showed “that the public seems to think of microplastics as something bad that might pollute the ocean and harm animal species” while fewer respondents mentioned spread in humans or food, as well as personal consequences. Moreover, Felipe-Rodriguez et al. reported that the public generally seems to have a low awareness of the potential sources of microplastics. The sources mentioned the most were fleece, clothing, and litter while food packaging was not named at all. The article further evaluated differences by sociodemographic characteristics and generally hopes to guide “tailored communications and interventions aimed at reducing plastic pollution and plastic waste.”
Felipe-Rodriguez M. et al (2022). “What does the public think about microplastics? Insights from an empirical analysis of mental models elicited through free associations.” Frontiers in Psychology. DOI: 10.3389/fpsyg.2022.920454
Katsara K. et al (2022). “Honey Quality and Microplastic Migration from Food Packaging: A Potential Threat for Consumer Health?” Microplastics. DOI: 10.3390/ microplastics1030030
Kim J. et al (2022). “Development and validation of analytical methods for detecting and identifying microplastics in salts, soy sauce, and salted pollock roe.” Journal of Food Composition and Analysis. DOI: 10.1016/j.jfca.2022.104856
This article was originally published by Lisa Zimmermann at the Food Packaging Forum.