Microplastic identification in German beer – an artefact of laboratory contamination?

Recent studies have detected microplastic fibres and particles in some food groups including honey and beer. The aim of this work was to replicate a method for microplastic analysis in beer. Several methodological pitfalls were detected in the literature method, including the staining agent rose bengal used in microscopic analysis, which false-negatively excludes some synthetic agents including the beer filtration aid polyvinylpolypyrrolidone (PVPP). False positive results may occur for non-plastic compounds such as starch or kieselgur. Other pitfalls in the analysis include the considerable background contamination, which did not allow differentiation between beer samples from blank samples in our laboratory. Specialized cleanrooms are required, but even then contamination may occur, because cleanroom classifications focus on small particles and may exclude the relevant sizes of microplastic particles. We judge the previous nonvalidated literature methods that reported positive findings in foods as unsuitable for the purpose of microplastic identification and believe that the results were artefacts due to contamination. Especially because beer production includes a microfiltration step to remove yeast cells, microplastic contamination due to raw materials is highly unlikely. So far, a validated methodology for microplastic detection in foods or beverages is unavailable.