PSI - Issue 68

Krastena Nikolova et al. / Procedia Structural Integrity 68 (2025) 845–853 K. Nikolova et al./ Structural Integrity Procedia 00 (2025) 000–000

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The addition of tea tree oil emulsion reduces the stress at break about 4 times in edible films, based on alginate, pectin, HPMC and almost 9 times for chitosan-based film. The reduction in the stress at break can be linked to the incorporation of essential oils (EOs) in the creation of edible films. While EOs make the films more flexible, they also weaken their durability. This occurs because the interaction between the polymer and EOs is less strong compared to the polymer-polymer interaction. Consequently, a barrier forms between the hydrocolloid polymer chains and the EOs. This leads to a decline in the mechanical properties of the edible films when EOs are present (Moghimi et al., 2017). The observed drop in the stress of chitosan/TTO film could be explained with the inhomogeneity in the film structure (see Fig. 5). The Young's modulus values follow the same relationship as the stress at break except for the HPMC film. In the latter case, a significantly greater elasticity is observed, which is determined by the strain at break. It is noteworthy that it almost does not change with the addition of essential oil. The addition of TTO to pectin-based and alginate based films the strain at break increase two and three times respectively, while it reduces by half in chitosan/TTO films. 4. Conclusions Four polysaccharide-based films with added tea tree oil were studied in the present research. It was proved by FT IR analysis that polysaccharide and oil interact by weak intermolecular forces. After the addition of the oil, the structure of the pectin and alginate films remained completely homogeneous, while the chitosan film was highly inhomogeneous with large oil aggregates. Based on the mechanical parameters of the studied films, it can be concluded that cellulose-based films are the most suitable as packaging material. Acknowledgements This study is financed by the European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project № BG-RRP-2.004-0009-C02. Special thanks to the Medical University of Varna and the European Union for the financial support provided for the publication of this paper. References ASTM D882-91 2017. Standard Test Methods for Tensile Properties of Thin Plastic Sheeting. American Society for Testing and Material: Philadelphia, PA, USA, Available online: https://www.astm.org/d0882-00.html (accessed on 2 June 2024). Avila-Sosa, R., Ochoa-Velasco, C.E., Navarro-Cruz, A.R., Palou, E., López-Malo, A. 2016. Combinational Approcahes for Antimicrobial Packaging: Chitosan and Oregano Oil in Antimicrobial Food Packaging; Elsevier Inc.: Amsterdam, The Netherlands, pp. 581–588. Bhatia, S., Al-Harrasi, A., Al-Azri, M.S., Ullah, S., Bekhit, A.E.-D.A., Pratap-Singh, A., Chatli, M.K., Anwer, M.K., Aldawsari, M.F., 2022. Preparation and Physiochemical haracterization of Bitter Orange Oil Loaded Sodium Alginate and Casein Based Edible Films. Polymers 14, 3855-3860. Chaharbaghi, E., Khodaiyan, F., & Hosseini, S. S., 2017. Optimization of pectin extraction from pistachio green hull as a new source. Carbohydrate polymers 173, 107–113. Chan-Matú, D. I., Toledo-López, V. M., Vargas, M. D. L. V. Y., Rincon-Arriaga, S., Rodríguez-Félix, A., & Madera-Santana, T. J., 2021. Preparation and characterization of chitosan-based bioactive films incorporating Moringa oleifera leaves extract. Journal of Food Measurement and Characterization 15(5), 4813-4824. Chhikara, S., & Kumar, D., 2022. Edible coating and edible film as food packaging material: A review. Journal of Packaging Technology and Research 6(1), 1-10. Christensen, S. H. 2020. Pectins. In Food hydrocolloids (pp. 205-230). CRC Press. Dilamian, M., Montazer, M., Masoumi, J., 2013. Antimicrobial electrospun membranes of chitosan/poly (ethylene oxide) incorporating poly (hexamethylene biguanide) hydrochloride. Carbohydrate Polymers 94, 364–371. Escárcega-Galaz, A.A., Sánchez-Machado, D.I., López-Cervantes, J., Sanches-Silva, A., Madera-Santana, T.J., Paseiro-Losada, P., 2018. Mechanical, structural and physical aspects of chitosan-based films as antimicrobial dressings. International Journal of Biological Macromolecule 116, 472–481. Freitas, C. M. P., Coimbra, J. S. R., Souza, V. G. L., & Sousa, R. C. S., 2021. Structure and applications of pectin in food, biomedical, and pharmaceutical industry: A review. Coatings 11(8), 922. Galus, S., Arik Kibar, E. A., Gniewosz, M., & Kraśniewska, K., 2020. Novel materials in the preparation of edible films and coatings—A review. Coatings 10(7), 674-679.