Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Lysozy Incorporated Antimicrobial Zein Films and Evaluation of Their Effectson Quality of Cold Stored Burgers(Izmir Institute of Technology, 2008) Uysal, İlke; Korel, FigenIn this study antimicrobial edible food packaging films were obtained by incorporation of hydrophilic partially purified lysozyme into hydrophobic zein films.The antimicrobial enzyme was incorporated into films by homogenization or stirring methods to increase its distribution in the films and to modify the film structure. The soluble and bound lysozyme activities of different zein films, as well as antimicrobial activity of films on different bacteria including Bacillus amyloliqufaciens, Listeria innocua, Eschericia coli, Pseudomanas fluorescens, Escherichia coli O157:H7, Salmonella typhimurium and Staphylococcus aureus and on cold stored burgers were tested. The lysozyme was combined with disodium EDTA to increase sensitivity of G(-) bacteria to enzymatic action. The films obtained by incorporation of 175 to 700 .g/cm2 lysozyme with stirring or homogenization methods showed good antimicrobial activity on most of the tested bacteria, except S. aureus. In general, due to their higher free soluble lysozyme content, the zein films incorporated with lysozyme by the stirring method gave higher antimicrobial activity on tested bacteria than films obtained by the homogenization method. However, the homogenization method caused better distribution of resulting antimicrobial activity in films than the stirring method. The films incorporated with 700 .g/cm2 lysozyme and 300 .g/cm2 disodium EDTA and prepared by stirring or homogenization method successfully suppressed the total viable counts and total coliform counts of cold stored turkey and beef burgers. The films also effectively reduced the oxidative changes in beef burgers during cold storage, but they showed no beneficial effects on beef color and sensory properties.Master Thesis Production of Functional Packaging Materials by Use of Biopreservatives(Izmir Institute of Technology, 2005) Mecitoğlu Güçbilmez, Çiğdem; Yemenicioğlu, AhmetIn this study, partially purified lyophilized lysozyme (LSZ) and lactoperoxidase (LPS) from chicken egg white and bovine whey were incorporated into zein and alginate films, respectively. The LSZ showed very low affinity to zein films. Thus, when zein films incorporated with 63-455 .g/cm2 (187-1318 U/ cm2) LSZ was exposed to release tests in distilled water, the enzyme released rapidly from the films with release rates of 9 to 29 U/cm2/min. The ethanol used in film making caused significant activation of the LSZ. Therefore, the released LSZ activity from zein films was mostly 130-300 % higher than the activity incorporated into films. On the other hand, the LPS incorporated into alginate films showed a very high affinity to these films and immobilized.The incorporation of 0.53 or 1.06 mg/cm2 proteins such as crude thermally processed chick-pea proteins (TP-CP) and sericine in combination with LSZ and LPS into zein or alginate films increased the antioxidant activity of edible films significantly.In zein films, the incorporation of antioxidant proteins reduced the total activity of LSZ released from the films between 50 % and 75 %, but increased the immobilized enzyme activity 3.5-15 fold. On the other hand, incorporation of antioxidant proteins into alginate films enhanced LPS activity slightly to moderately. The results of this study clearly showed the good potential of edible films and natural biopreservatives in active packaging.Master Thesis Development of Ph-Controlled Triggering Mechanisms for Controlled Release of Lysozyme(Izmir Institute of Technology, 2011) Boyacı, Derya; Yemenicioğlu, AhmetIn this study, zein and whey protein (WP) based films and their blends and composites have been prepared to obtain pH-controlled triggering mechanisms for controlled release of lysozyme. The total amount of lysozyme released from standard zein films was not considerably affected from changes in pH between 7.3 and 5.3 since this hydrophobic biopolymer lacked charged ionisable groups to bind lysozyme ionically. In contrast, incorporation of lentil protein isolate (LPI) into zein created a composite structure and caused binding of positively charged lysozyme (pI>9.0) on negatively charged groups of LPI (pI: 4.5-6) within the film matrix in release medium with pH between 5.3 and 7.3. The amount of bound lysozyme in zein-LPI composites increased linearly as LPI concentration increased between 1,5 and 4,5 mg/cm2 at pH 7.3. The release of bound enzyme could be triggered by reducing pH of release medium from 7.3 to 4.3, down below pI of LPI. On the other hand, films of WP (pI≈5.2) bind considerable amount of lysozyme due to their inherent net negative charges close to neutrality. The release of bind lysozyme could be trigged as pH of release medium reduced from 6.0 to 3.0, down below the pI of WP. The preparation of WP-oleic acid blend and WP-bees wax composites increased the film porosity and amounts of released lysozyme from films at pH 4.5 and 5.0, by 2-4 and 1.2-1.5 folds, respectively. The zein and WP based films containing 0.7 to 1.4 mg/cm2 lysozyme showed good antimicrobial activity against Listeria innocua. This work showed the potential of creating pH-controlled release systems during antimicrobial packaging of food.