Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Subject: search.filters.subject.Food--Packaging

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Now showing 1 - 7 of 7
  • 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, Figen
    In 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
    Development of Antimicrobial Protective Food Coating Materials From Edible Alginate Films
    (Izmir Institute of Technology, 2007) Yener, Fatih Yalçın Güneş; Korel, Figen
    Consumer interests in high quality, healthy, convenient and safe food continue to increase, presenting food processors with new challenges to which functional edible coating and film concepts offer potential solutions. The interest in the research of edible film which has many advantages and applications has increased during last decade.There is a particular interest in the use of antimicrobial biopreservatives in edible films and to increase food safety without application of chemical preservatives. In this study,we have developed antimicrobial or protective edible films by incorporation of antimicrobial enzyme lactoperoxidase or protective cultures (Lactobacillus delbrueckii subsp. lactis and Lactobacillus plantarum) into alginate films, respectively. The main objective of this research was to increase food safety by using lactoperoxidase or lactic acid bacteria incorporated into alginate films. The results obtained in the study showed that in reaction mixtures, the lactoperoxidase system has antimicrobial activity against E. coli, L. innocua, and P. fluorescens. The developed lactoperoxidase incorporated antimicrobial films also reduced the total microbial load of a selected seafood during cold storage. The lactic acid bacteria, used in edible films for the first time, also successfully incorporated into alginate films. The bacteria showed sufficient stability in alginate films and at surface of red meat during cold storage. The results of this study clearly showed the good potential of using lactoperoxidase and lactic acid bacteria incorporated alginate films in food packaging. The developed films can be used in antimicrobial packaging or protective packaging. However, further studies are needed to show the beneficial effects of developed films on different food systems.
  • Master Thesis
    Preparation and Characterization of Antimicrobial Polymeric Films for Food Packaging Applications
    (Izmir Institute of Technology, 2007) Gemili, Seyhun; Alsoy Altınkaya, Sacide
    In this study, cellulose acetate (CA) based antimicrobial packaging materials containing lysozyme as an antimicrobial additive were developed. In order to achieve appropriate controlled release of antimicrobial agent, the structure of the films were changed from highly asymmetric and porous to dense ones by modulating the composition of the initial casting solution. The effectiveness of the films were then tested through measurement of soluble and immobilized lysozyme activity, release kinetics and antimicrobial activity on selected microorganisms. The highest release rate, soluble lysozyme activity and resulting antimicrobial activity (on E.coli) was obtained with the film prepared from 5 % CA solution including 1.5 % lysozyme. Increasing CA content in the casting solution decreased the porosity of the films, hence, reduced the release rate, maximum released activities and the antimicrobial activities of the films. On the other hand, immobilized activities and the tensile strength of the films increased. The mechanical properties of the antimicrobial films cast with 5 % and 10 % CA were similar to those of lysozyme free CA films. However, significant reductions in tensile strength and elongation values were observed for the antimicrobial films prepared with 15 % CA. Differences in the release rates, soluble, immobilized and antimicrobial activities at porous and dense surfaces of the films suggest that different surfaces of CA films can be employed for antimicrobial packaging according to the targeted shelf-life of the food products. When the films made with 5 % CA were stored at 4 °C for a maximal period of 105 days, an increase in soluble lysozyme and antimicrobial activities of the films were observed. The results demonstrate that CA films prepared in this study show promising potential to achieve controlled release in antimicrobial packaging.
  • Master Thesis
    Preparation and Characterization of Corn Zein Coated Polypropylene (pp) Films for Food Packaging Applications
    (Izmir Institute of Technology, 2007) Atik, İsa Doğan; Tıhmınlıoğlu, Funda
    The plasticized corn-zein coatings on polypropylene (PP) films as an alternative to multilayer packaging films consisting of non-degradable polymers were prepared to evaluate barrier, mechanical, thermal, surface and optical properties of the resulting coated film, as affected by coating formulation (solvent, corn-zein, plasticizer concentration, and plasticizer type). PP films coated with corn zein were obtained through a simple solvent casting method. Corn-zein with different amounts (5% and 15%) was dissolved in 70% and 95% aqueous ethanol solution at 50oC, respectively. Solutions of corn-zein plasticized by polyethylene glycol (PEG) and glycerol (GLY) with various levels (20% and 50%) were applied on corona-discharged-treated PP film. The resulting corn-zein coated PP films showed good appearance, flexibility and adhesion between the coating and the base film. The coated PP films showed a significant (P<0.05) increase in barrier (water and oxygen) properties and improvement in mechanical properties when coating formulation consisted of higher corn-zein content and lower amount of GLY as plasticizer. Furthermore, zein coating increased the service temperature range of the PP films, and promised good printability on the surface due to contact angle results. The statistical analysis defined that the key parameters of coating formulation that had major effect on the final properties of coated PP films as corn-zein concentration, plasticizer concentration, and plasticizer type while ethanol concentration was found to be as less effective parameter compared to others. In conclusion, corn zein coatings with appropriate formulation on PP films could have potential as an alternative to conventional synthetic coatings for food packaging applications.
  • Master Thesis
    Preparation of Controlled Release Antimicrobial Food Packaging Materials
    (Izmir Institute of Technology, 2009) Uz, Metin; Alsoy Altınkaya, Sacide
    In this study, potassium sorbate (Psb) incorporated cellulose acetate (CA) films were developed for antimicrobial food packaging applications. The most significant characteristics of these films were their asymmetric porous structure. To achieve appropriate controlled release of Psb, the structure of the films were changed by manipulating the initial casting composition, wet casting thickness, drying temperature and number of layers. The effectiveness of the films was tested through measurement of release kinetics and antimicrobial activity on selected microorganism, Penicillium commune. It was found that as the initial casting composition, wet casting thickness and drying temperature increase, porosity and pore size of the films reduce leading to slower release rates. The most significant parameter affecting the release was found as the number of layers. The diffusion coefficient of Psb through multilayer films decreased by two orders of magnitude compared with single layer. Drying-induced crystallization was observed in single layer films. Higher number and larger size of crystals were observed in more porous films. Fast initial release of Psb from the single layer films which is controlled by Fickian diffusion was followed by a decreasing release rate due to slow crystal dissolution. However, in multilayer films, release rate is regulated onl by diffusion of Psb through the film. All the films prepared showed growth inhibition on P. commune. The antimicrobial activities of single layer films were found higher than the multilayer films. The results of this study demonstrated that Psb incorporated CA films show promising potential for controlled release in antimicrobial packaging.
  • Master Thesis
    Production of Functional Packaging Materials by Use of Biopreservatives
    (Izmir Institute of Technology, 2005) Mecitoğlu Güçbilmez, Çiğdem; Yemenicioğlu, Ahmet
    In 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, Ahmet
    In 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.