An electrochemical biosensor for the detection of genetically modified food components is presented. The biosensor was based on 21-mer single-stranded oligonucleotide (ssDNA probe) specific to either 35S promoter or nos terminator, which are frequently present in transgenic DNA cassettes. ssDNA probe was covalently attached by 5’-phosphate end to amino group of cysteamine self-assembled monolayer (SAM) on gold electrode surface with the use of activating reagents – water soluble 1-ethyl-3(3’- dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxy-sulfosuccinimide (NHS). The hybridization reaction on the electrode surface was detected via methylene blue (MB) presenting higher affinity to ssDNA probe than to DNA duplex. The electrode modification procedure was optimized using 19-mer oligoG and oligoC nucleotides. The biosensor enabled distinction between DNA samples isolated from soybean RoundupReady^® (RR soybean) and non-genetically modified soybean. The frequent introduction of investigated DNA sequences in other genetically modified organisms (GMOs) give a broad perspectives for analytical application of the biosensor.

The main function of food packaging is to maintain food’s quality and safety. The use of active packaging, including antimicrobial materials, can significantly extend the shelf life of food. Many of these packaging solutions are based on the application of polymer films containing metal nanoparticles (e.g., Ag, Au, Cu) or metal oxides (e.g., TiO₂, ZnO, MgO). However, the use of iron nanoparticles is rarely mentioned. In the study, polylactide (PLA) films containing zero-valent iron (ZVI) were made by casting method. Pure PLA films and PLA films with the addition of Fe₂O₃ were used as comparative materials. The composition and structure of ZVI/PLA films were evaluated with scanning electron microscopy. The XRD spectra performed on ZVI/PLA films confirmed the presence of iron in the packaging material and revealed their oxide form (Fe₂O₃). The addition of zero-valent iron in the concentration 1%, 3%, or 5% resulted in the formation of crystallographic planes measuring 40.8, 33.6, and 28.6 nm, respectively. The color and gloss of the films, and their antimicrobial activity against bacteria (Bacillus subtilis, Escherichia coli, Staphylococcus epidermidis) and fungi (Geotrichum candidum, Rhodotorula rubra) were also examined. The PLA films with addition of 3% of ZVI (w/w) inhibited the growth of all tested organisms in contrast to PLA and PLA/Fe₂O₃ films. The addition of ZVI to polymer matrix caused changes in its appearance and optical properties. The ZVI/PLA coating used on polyolefin film allowed to extend the shelf life of goat cheese packed in examined material to 6 weeks. Considering the antimicrobial properties of the ZVI/PLA films and PLA biodegradability the obtained material can be successfully applied in the food industry.

The aim of the study was to compare the content of selected phytochemicals as well as the antioxidant and antimicrobial potential of the leaves of Prunus padus L. and Prunus serotina L., as there is very little research on this subject in the literature. Therefore, it is used to deepen knowledge on this subject. In addition, an electrochemical test was also carried out, which was not yet available for the above plants. Antibacterial studies have also been deepened to include the analysis of new strains of bacteria and fungi, which has not been studied earlier. The water extracts of P. padus using the utra-performance liquid chromatography (UPLC) system showed a higher content of both phenolic acids and flavonols (651.77^b ± 18.12 mg/100 g dw for acids and 3.85^b ± 0.08 mg/100 g dw for flavonols, respectively). Ferulic and p-coumaric acids were the dominant polyphenols in leaves. Extracts from P. padus showed higher activity against DPPH radical, which was 6.62^b ± 0.06 mg TE/1 g dw, as well as higher antioxidant capacity, measured using 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) cation radical (37.39^b ± 3.81 mg TE/g dw). The higher antioxidant potential of P. padus was confirmed based on the oxidizing potentials of electroactive compounds present in them. Stronger inhibition against Enterococcus faecium and Klebsiella pneumoniae was found for P. padus, whereas P. serotina extract was more potent against Enterococcus faecium bacterium. It has been shown that P. padus can be an attractive raw material with antioxidant and antimicrobial properties that can be used on a much wider scale in food technology than its current application.