Biomaterials based on polyelectrolyte complexation are an innovative concept of coatings and packaging production to be applied in a wide range of food products. The aim of this study was to obtain and characterize a sodium alginate–chitosan complex material with variable degree of polyion interactions by complexation of oppositely charged polysaccharides. In order to characterize polyelectrolyte complexes, theromogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), matrix-assisted laser desorption/ionization technique with time of flight analyzer (MALDI-TOF), and scanning electron microscopy (SEM) were performed. TGA analysis showed that thermal decomposition temperature depends on the polymer ratio (R) and thermal resistance of samples was improved by increasing chitosan dosage. Accordingly to DMTA results, polyelectrolyte complexation led to obtain more flexible and resistant to mechanical deformation materials. Comparative analysis of the FTIR spectra of single polyelectrolytes, chitosan and alginate, and their mixtures indicated the formation of the polyelectrolyte complex without addition of reinforcing substances. MALDI-TOF analysis confirms the creation of polyelectrolyte aggregates (~197 Da) in samples with R ≥ 0.8; and their chemical stability and safety were proven by NMR analysis. The higher R the greater the number of polyanion–polycation aggregates seen in SEM as film morphology roughness.

The effects of helium and argon plasma treatments on inactivation of both pure bacterial cultures inoculated onto the surface of agarized media and the surface microbiota of meat were investigated. Cold plasmas were generated by high voltage discharge at low pressure (20 kPa) for 2, 5, and 10 min. The number of viable microorganisms was determined using a plate count method. Morphological changes were observed using scanning electron microscopy (SEM). Microbial log reduction depended on time of exposure and type of gas used. After a 10-min treatment with helium plasma, the total number of microorganisms, yeasts and molds, and psychrotrophic microorganisms was reduced in the range of 1.14–1.48 log cycles for pork and 0.98–2.09 log cycles for beef. A significant reduction of 2.00 log for Bacillus subtilis and Yersinia enterocolitica was achieved within 2 min of helium plasma treatment. Similar results were obtained for Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens after 5 min and 10 min of exposure. SEM revealed disruption and lysis of E. coli cells treated with helium plasma for 10 min, suggesting a bactericidal effect.

The aim of the study was to investigate the effect of using direct electric current (DC) of 400 mA for five minutes on the physiochemical properties of gelatine (2%, 4%, and 8%), carrageenan (1.5%, 2%, and 2.5%) and sodium alginate (0.75%, 1%, and 1.25%) hydrosols with different sodium chloride concentration. The pH, oxidation-reduction potential (ORP), electrical conductivity (EC), available chlorine concentration (ACC) and rheological parameters were measured. Moreover, Fourier transform infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analysis were carried out. The results have shown that pH, ORP, EC and ACC values are changed upon applying DC and the magnitude of change depends on the concentration of the polymer and the addition of sodium chloride. After seven days of storage, the ACC of the samples exposed to DC decreased by 88%–96%. The FT-IR spectra demonstrated that the structure of gelatine, carrageenan and sodium alginate are not significantly affected by DC. Furthermore, the use of DC did not affect the flow and gelation temperature of the hydrosols. These results suggest that the use of DC did not cause undesirable changes in hydrosols layer and these innovative materials can be used, e.g., for food preservation.