| Abstrakt: |
The issue of global contamination with microplastics (MPs) has become a critical issue globally due to high levels of MPs in various ecosystems and certain food products. This study aims to investigate the presence of microplastics in branded milk, in terms of chemical composition and toxic effect on humans. An absolute novelty of this study consisted in the development of a method for isolating the microplastics from the matrix of the branded milk samples using ultrasound technique at constant temperature and pressure, high-performance vacuum filtration method with various high-purity filtration membranes (e.g., cellulose, glass fiber, quartz, nylon, or polytetrafluoroethylene - PTFE). The milk samples selection was based on the quality offered by the producers, the popularity of the brand, the purchase degree, the type of packaging and the product cost. The samples were purchased from hypermarkets of Romania, the fat content varied between 1.5-3.8%, Tetra Pack, plastic or glass packaging. A total of 10 different brands were chosen for this study. The samples were divided into two categories (non-Bio and Bio milk). On the other hand, the combined application of the structure sensitive technique Fourier-transform infrared µ-spectroscopy in conjunction with different approaches of optical microscopy and scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), was a significant objective of this study, to elucidate the type, structure, and chemical composition of MPs. Microplastics were identified in all 16 analyzed samples (10 non-Bio milk samples and 6 Bio milk samples). Regarding the total number of microplastics identified in the two types of milk (non-Bio and Bio), the Bio milk samples recorded a higher total number of microplastics (166 polymer fibers), compared to the non-Bio milk samples (143 polymer fibers); the identified colors were black (mostly), blue, yellow, brown and red. By analyzing the MPs sizes was observed that length varied from tens of micrometers to a few centimeters in some cases and the thickness reached 15 µm and even more for various samples. From visual and chemical point of view the structure was mostly like polypropylene wires but smaller and having glossy mate or transparent appearance. The MPs investigated by SEM-EDS have a filiform structure, their morphology being similar. This morphology is characterized by finely textured surfaces with medium roughness and shows longitudinal microcracks. The EDS results identified the presence of C, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, and Ti on the surface of the microplastics. Most of the elements identified in concentration less than 5% represent milk constituents. Likewise, the presence of aluminum and titanium can be explained by the way the milk is packaged, by some pigments used to color the polymer or by the accidental ingestion. [ABSTRACT FROM AUTHOR] |
