Degradation of chitosan-based bioplastics in terrestrial environment

Embalaža za hrano ima med plastičnimi izdelki najkrajši rok uporabe, saj je pogojena z rokom uporabnosti hrane, ki jo ščiti. Pri hitro pokvarljivi hrani in izdelkih, ki so namenjeni za takojšnje zaužitje, je to lahko tudi manj kot en dan. Po uporabi pa ta plastična embalaža postane odpadek, ki ga večinoma recikliramo, lahko pa konča na deponiji, v sežigalnicah ali v naravi. Iskanje alternativne embalaže je predmet več raziskav in ena izmed predlaganih možnosti so filmi na osnovi hitozana z dodatkom različnih naravnih ekstraktov, ki izboljšajo antioksidativne, mehanske in antimikrobne ter zaščitne lastnosti (UV-zaščita, CO2, O2 in vlaga). Filmi, osnovani iz naravnih polimerov, so lahko obetavna alternativa zaradi svoje potencialne biorazgradljivosti v naravnem okolju. V magistrskem delu sem preverila biorazgradljivost filmov na osnovi hitozana z dodanim hrastovim ekstraktom v treh različnih prsteh: kompostu, vrtni prsti in vinogradniški prsti. Razgradljivost filmov sem spremljala na podlagi izgube mase, spremembe v vsebnosti polifenolov, analize FT-IR in s pregledom površine z vrstičnim elektronskim mikroskopom. Preverila sem tudi, kako vsebnost vlage v prsti vpliva na uspešnost razgradnje filmov. Rezultati so pokazali, da se filmi na osnovi hitozana brez dodanega ekstrakta razgradijo v vseh vrstah prsti in pri vseh testiranih vlažnostih. Filmi z dodanim hrastovim ekstraktom pa so popolnoma razgradljivi v vrtni prsti in v kompostu, ne pa v prsti iz vinograda. Pokazalo se je tudi, da dodatek vode k prsti upočasni hitrost razgradnje filmov.Among plastic products, food packaging is used for the shortest period of time because it is determined by the food shelf life. With perishable foods and products meant for immediate consumption, it can be used for even less than one day. After use, this plastic packaging becomes waste, which can be recycled, ends up in landfills, in incinerators or in the environment. Many studies are focused on finding an alternative packaging, and one of the proposed possibilities are chitosan-based films with various natural extracts that improve antioxidative, mechanical and antimicrobial properties and enhance barrier properties (UV protection, CO2, O2 and water). Because of their potential biodegradability, biopolymer-based films are a promising alternative to conventional plastic. In the master’s thesis, I studied the biodegradability of chitosan-based films with added oak extract in three different types of soil: compost, soil for gardening and soil from vineyards. Degradability was tracked through mass loss, change in polyphenolic content, FT-IR analysis and by examination of surface using a scanning electron microscope. The impact of increased soil humidity was also evaluated. The results have shown that chitosan-based films with no added extract are biodegradable in all types of soil and at both tested water contents. Films with added oak extracts were completely biodegradable in compost and gardening soil, but not in vineyard soil. It was also discovered that adding water to soil slowed down the rate of film degradation