Protimikrobna aktivnost embalažnih folij s premazom hitozana in kombinacijo rastlinskih izvlečkov

Krajnc, Tina (author), Smole-Možina, Sonja (mentor), Fras Zemljič, Lidija (co-mentor)

Dobre barierne lastnosti in nizka cena so glavni razlogi masovne proizvodnje in uporabe petrokemičnih polimerov za embaliranje hrane, žal pa zaradi zelo dolgotrajne razgradnje močno obremenjujejo okolje. Zato se pojavlja velika potreba po biorazgradljivih materialih iz obnovljivih virov, med katere sodi tudi polimlečna kislina (PLA) kot osnova embalažne folije za razvoj aktivne embalaže. Namen magistrskega dela je bil izdelati bioaktivno živilsko folijo na osnovi PLA, na katero smo z valjčkanjem nanesli sloj hitozana in nato še sloj rastlinskih izvlečkov. Izvedli smo številne fizikalno-kemijske analize in testirali bioaktivnost folij. Z analizami zeta potenciala, spektrov ATR-FTIR in analizo XPS smo potrdili uspešen nanos hitozana in rastlinskih izvlečkov. Pomembna lastnost embalažne folije je dobra omočljivost, ki smo jo določili z meritvami kontaktnega kota. Z nanosom izvlečkov smo stične kote uspešno zmanjšali in izboljšali omočljivost folij, kar je pomembno za praktično uporabo. Za obstojnost živila je pomembna čim manjša prepustnost embalažne folije za kisik. Z nanosom slojev smo še izboljšali dobre barierne lastnosti PLA za povprečno 7,6 %. Določili smo tudi desorpcijo hitozana in izvlečkov s folij, saj je le-ta za uporabo na živilih omejena. Desorpcija hitozana je presegla omejitev, desorpcija izvlečkov pa je bila sprejemljiva. Antioksidativno aktivnost embalažnih folij s premazi smo določili z metodama ABTS in DPPH in potrdili dobro antioksidativno aktivnost dodanih rastlinskih izvlečkov. Protimikrobno aktivnost folij smo testirali proti bakterijama Escherichia coli in Pseudomonas fragi ter proti glivam Saccharomyces cerevisiae, Penicillium verrucosum ter Aspergillus flavus. Folije z nanosom hitozana in izvlečkov so bile protimikrobno aktivne proti vsem testiranim mikroorganizmom, učinkovitost pa je padala v enakem zaporedju, kot so navedeni tarčni mikroorganizmi.

• Language: Slovenian
• Keywords: pakiranje živil, aktivna embalaža, rastlinski izvlečki, hitozan, PLA, antioksidativna aktivnost, protimikrobna aktivnost
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [T. Krajnc]
• Year: 2023
• PID: 20.500.12556/RUL-151709
• UDC: 621.798.1:664.0:579.67:547.9
• COBISS.SI-ID: 168884995
• Publication date in RUL: 18.10.2023

Secondary language

• Language: English
• Title: Antimicrobial activity of packaging foils coated with chitosan and combination of plant extracts

Abstract

Good barrier properties and low prices are one of the leading causes of the mass production of petrochemical polymers for food packaging, which, however, represent a very large part of the pollution problem. Because of this, there is a great need for biodegradable materials from renewable sources, among which is also polylactic acid (PLA) as the basis of packaging film, for the development of active packaging. The purpose of the master's thesis was to produce a biodegradable active food film, where PLA was used as a base, on which a layer of chitosan and then a layer of plant extracts were applied by rolling. We performed several physico-chemical analyzes and evaluated the foils' bioactivity. The successful application of chitosan and plant extracts was confirmed by analyzes of zeta potential, ATR-FTIR spectra and XPS analysis. An important property of the packaging film is its good wettability, which was determined by measuring the contact angle. By applying the extracts, we successfully reduced the contact angles and improved the wettability of the foils, which is important for practical use. For extended shelf-life of the food, it is important to reducethat the oxygen permeability of the packaging is as low as possible. By applying the layers, we improved the already good barrier properties of PLA by an average of 7.6%. We also determined the desorption of chitosan and extracts from foils, as this is limited for use on food. Desorption of chitosan exceeded the limit, while the desorption of extracts was acceptable. The antioxidant activity of coated packaging films was determined using the ABTS and DPPH methods, and the antioxidant activity of the addition of plant extracts was confirmed. The antimicrobial activity of the films was tested against the bacteria Escherichia coli and Pseudomonas fragi and against the fungi Saccharomyces cerevisiae, Penicillium verrucosum and Aspergillus flavus. Films coated with chitosan and extracts şhowed antimicrobial activity against all microorganisms tested, with efficacy decreasing in the same order as the target microorganisms are listed.

• Keywords: food packaging, active packaging, plant extracts, chitosan, PLA, antioxidant activity, antimicrobial activity