Blown film extrusion of PBAT/TPS/ZnO nanocomposites for shelf-life extension of meat packaging

Biodegradable polymers typically have inferior barrier properties compared to petroleum-based nonbiodegradable plastic. The addition of zinc oxide nanoparticles may enhance the functional properties of biodegradable packaging and extends the shelf life of packaged foods. Polybutylene adipate-co-terephthalate (PBAT) and thermoplastic starch (TPS) blended ZnO (1-5%) nanocomposite films were developed via blown extrusion for functional active meat packaging. The nanocomposite film morphology showed agglomeration of the nanoparticles, causing poor mechanical properties. Nanovoids formed at the interface between the polymer and nanoparticles, increasing permeability. Dispersion of ZnO nanofillers modified CO and C-O ester bonding in PBAT and increased hydrogen bonding with TPS. The interaction between ZnO and polymers increased the dispersion and reduced the agglomeration of nanoparticles. The highest ZnO content at 5% resulted in a stronger interaction between ZnO and TPS due to increased amorphous starch content, which improved homogeneous dispersion within the matrices, reducing nanoparticle size. The ZnO nanocomposite films reduced lipid oxidation and delayed microbial growth, resulting in a lower total viable count, lactic acid bacteria and yeast and mold in packaged pork meat. Higher ZnO concentrations from 3% showed microbial inhibitory effects. The growth of microorganisms was controlled by residual oxygen, morphology of the films and nanoparticle characteristics. The nanocomposite films effectively extended the shelf life by more than 3 days under refrigerated conditions.

Nanopharmaceuticals (Au-NPs) after use: Experiences with a complex higher tier test design simulating environmental fate and effect

The current environmental hazard assessment is based on the testing of the pristine substance. However, it cannot be excluded that (nano)pharmaceuticals are excreted into sewage during the use phase followed by entry into wastewater treatment plants (WWTPs). Sorption to sewage sludge or release via effluent can result in modified ecotoxicological effects which possibly can only be detected with a modified test approach. The objective of our study was to investigate a realistic exposure scenario for metallic nanoparticles (NPs) in pharmaceutical products, excreted into effluent, and released into the environment after treatment in WWTPs. The test approach was illustrated by using gold (Au) NPs. Effluent from model WWTPs were investigated in aquatic tests (Daphnia magna, fish cell lines). Sewage sludge was used as a sole food source (Eisenia fetida) or mixed with soil and used as test medium (soil microorganisms, Folsomia candida, Enchytraeus crypticus). To cover the aspect of regulation, the test systems described in OECD-test guidelines (OECD TG 201, 211, 220, 232, 249, 317) were applied. Modifications and additional test approaches were included to meet the needs arising out of the testing of nanomaterials and of the exposure scenarios. The results were assessed regarding the suitability of the test design and the toxicity of Au-NPs. Except for activated sludge as a sole food source for E.fetida, the selected test approach is suitable for the testing of nanomaterials. Additional information can be gained when compared to the common testing of the pristine nanomaterials in the standardized test systems. Effects of Au-NPs were observed in concentrations exceeding the modeled environmental.

Thermoplastic starch blown films functionalized by plasticized nitrite blended with PBAT for superior oxygen barrier and active biodegradable meat packaging

Functional bioplastic packaging was produced from thermoplastic starch (TPS) with nitrite (1-5%) and polybutylene adipate terephthalate (PBAT) (PBAT/TPS at 30/70 and 40/60) via blown-film extrusion. TPS-nitrite interaction increased thermal destabilization and decreased α-relaxation temperature of TPS phase, indicating improved plasticization and disruption of starch granules. Nitrite modified C=O bonding of PBAT and improved compatibility with TPS networks, resulting in compact microstructures that reduced oxygen and water vapor permeability. Films containing nitrite showed up to 39.7% decrease (p≤0.05) in mechanical properties while effectively improving and stabilizing redness of vacuum-packaged pork during storage for 12 days. Nitrite release led to up to 0.66 ppm residual nitrite, which corresponded to formation of nitrosyl myoglobin (3.4-9.6 ppm), and effectively reduced total viable count, lactic acid bacteria and yeast and molds (p≤0.05). Stabilized lipid components also increased with increasing nitrite. Novel nitrite-containing biodegradable film enhanced functional properties and retained quality of packaged meat.