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Starch-based pH-sensing films with bacterial nanocellulose (BNC) and red cabbage anthocyanins (RCA) as active components were investigated in this research. Their structural, physical, surface and colorimetric properties were analyzed, mainly as a function of BNC concentration. The aim of the research was to relate the changes in the intermolecular interactions between the components of the films (starch, anthocyanins and BNC) to the physical, surface and colorimetric properties that are important for the primary intended application of the produced films as pH indicators in smart packaging. The results showed that maize starch (MS) was more suitable as a matrix for the stabilization of anthocyanins compared to potato starch (PS). PS-based films showed a lower value of water contact angle than MS-based films, indicating stronger hydrophilicity. The swelling behavior results indicate that the concentrations of BNC in MS-based films (cca 10%) and the concentration of about 50% BNC in PS-based films are required if satisfactory properties of the indicator in terms of stability in a wet environment are to be achieved. The surface free energy results of PS-based films with BNC were between 62 and 68 mJ/m 2 and with BNC and RCA between 64 and 68 mJ/m 2 ; for MS-based films, the value was about 65 mJ/m 2 for all samples with BNC and about 68 mJ/m 2 for all samples with BNC and RCA. The visual color changes after immersion in different buffer solutions (pH 2.0-10.5) showed a gradual transition from red/pink to purple, blue and green for the observed samples. Films immersed in different buffers showed lower values of 2 to 10 lightness points (CIE L*) for PS-based films and 10 to 30 lightness points for MS-based films after the addition of BNC. The results of this research can make an important contribution to defining the influence of intermolecular interactions and structural changes on the physical, surface and colorimetric properties of bio-based pH indicators used in smart packaging applications.

In this study, the surface modification of thin ink films with added nanoparticles was used to improve the functional properties of ink applied on paperboard substrates. The surface modification was performed by additional exposure of the samples to xenon radiation. Anatase TiO 2 , rutile TiO 2 and ZnO were added to the base ink. The effect of surface modification on the surface, structural, and mechanical properties of the printed ink films was determined by FTIR-ATR spectroscopy, calculating the surface free energy and adhesion parameters, performing the rub resistance test of the printed samples, and by measuring the resistance to bending. Color measurements on the ink films were performed in order to observe the optical properties of unmodified and modified samples. The results showed that surface modification significantly improved the adhesion properties of the thin ink films and the mechanical properties of the samples. The results obtained on uncoated and coated paperboard showed that the addition of rutile TiO 2 and ZnO nanoparticles had the greatest effect on the rub resistance of the ink films. The results of the color analysis showed that the addition of nanoparticles did not change the optical properties of the modified ink films and that rutile TiO 2 and ZnO nanoparticles improved the lightfastness of the applied ink films.