Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Antimicrobial Protective Food Coating Materials From Edible Alginate Films(Izmir Institute of Technology, 2007) Yener, Fatih Yalçın Güneş; Korel, FigenConsumer 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 of Controlled Release Antimicrobial Food Packaging Materials(Izmir Institute of Technology, 2009) Uz, Metin; Alsoy Altınkaya, SacideIn 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 Preparation and Characterization of Polypropylene Based Composite Films(Izmir Institute of Technology, 2001) Pehlivan, Hilal; Tıhmınlıoğlu, FundaIn the scope of this study, preparation of silver . natural zeolite reinforced polypropylene (PP) composite system possessing antibacterial properties via ion exchange process and characterization by means of different techniques (FTIR, TGA, DSC, mechanical tests, optical microscopy) were aimed. It has been established that zeolites are suitable for removing Ag ions from silver containing solutions and that silver zeolites are increasingly investigated as germicidal, bactericidal, antifungal, and antiseptic components in different compositions (Hagiwara 1990, Kawahara 2000, Klasen 2000).In the present study, prior to the ion exchange studies, water sorption behavior of PP . clinoptilolite rich natural zeolite composites was investigated, since the ion exchange process was to be conducted in aqueous media. It was observed that a hydrophobic polymer, PP attained the property of water sorption due to the porous structure of the composite films. The effective diffusivity of liquid water in the PP-zeolite composites prepared by hot press and extrusion techniques varied in the range of 0.3- 9.9 x10-10 and 0.1 - 3.3 x10-12 cm2/s, respectively. Silver loading to PP - zeolite composites was provided by means of two different methods. In Method I, PP - zeolite composite films were treated with a variety of silver ion containing solutions (5 to 50 ppm AgNO3 solution), whereas in Method II silver exchanged zeolite minerals (prepared with initial AgNO3 concentrations of 50, 500, and 5000 ppm) were molded with PP in the presence of DOP (Dioctyl Phthalate). The amounts of Ag+ loaded per gram of zeolite for initial AgNO3 concentrations of 50, 500, and 5000 ppm were determined as 4.36, 27.85, and 183.78 mg, respectively. Antibacterial activity tests against E.coli indicated that the samples obtained in Method II were superior to those prepared by Method I since the penetration of silver ions to the zeolite phase was limited by the PP phase in the case of Method I. However, the discoloring effect of silver ion was readily observed for the samples prepared by Method II as indicated by the discoloration parameters. The release of Ag+ to water was found to be negligible as reported in literature leading to long . term antibacterial activity.The thermal characterization studies showed that the addition of the zeolite increased the crystallinity of the structure acting as a nucleating agent in PP crystallization as well as retarded the degradation temperature of PP. At low silver concentrations, the zeolite behaved as a decelerating agent in PP, however at higher silver concentrations, the composites degraded at a faster rate than pure PP. Yet the activation energy values for the thermal decomposition reactions of Method II was considerably lower indicating that the decomposition has been accelerated by the presence of silver.It was found that the addition of the zeolite into the PP matrix decreased the density of pure PP (0.89 g/cm3) due to the formation of voids. However, a systematic approach was not observed with the increasing zeolite content as a consequence of the uneven zeolite distribution. On the other hand, a considerable enhancement was noticed for the tensile tested film densities changing between 0.58 - 0.78 g/cm3, which are in a better agreement with the commercially desired range (0.6 - 0.65 g/cm3) for packaging applications of PP composites. Mechanical tests indicated that the addition of the zeolite tended to decrease the yield stress values while a slight decrease was observed for Young moduli. The effect of silver on the Young Modulus values of the composites is not quite significant, however the yield stress values increased from 23.6 to 29.5 MPa with the increasing silver concentration.Consequently, of all the composite films prepared by Method II, the ones loaded with 4.36 (mg Ag+/g zeolite) containing 2, and 4 % wt zeolite were selected to be the most appropriate, considering the thermal, mechanical, and structural characteristics as well as the discoloring actions.Master Thesis Efficacy of Natural Antimicrobials on Food-Borne Pathogens and Their Applications(Izmir Institute of Technology, 2008) Eroğlu, Erdal; Soyer Dönmez, FerdaMicrobial contamination of food products increases the risk of food-borne infections and intoxications. In recent years, more studies have been performed for development of natural alternatives to control the growth of pathogenic microorganisms in food rather than chemical origin. In the present study, natural antimicrobial agents from different sources, activated lactoferrin-(ALF), rosemary extract-(RE), jenseniin-G (JG) and natamycin-(NA) were used.The antimicrobial activity of agents (ALF-RE-JG) and their combinations against L. monocytogenes, E. coli O157:H7 and S. Enteritidis, and NA against A. niger and P. roquefortii was tested. These antimicrobials, found effective in vitro, applied also on meat and cheese samples. The minimum inhibitory concentrations (MIC) of ALF, RE and JG against pathogens were determined via disc diffusion and microtiter plate growth assay. Dipping method was applied on meat samples to test the efficacy of antimicrobials. MIC of NA was determined via disc diffusion assay. NA was applied on cheese samples to test the efficacy against both molds by dipping method.The data from microtiter well plate assay showed that ALF is effective on three pathogens. Rosemary extract inhibited only growth of L. monocytogenes and JG did not show any significant activity on the growth of same pathogens. RE enhanced the activity of ALF on E. coli O157:H7. Neither individual activity nor synergistic activity was determined by disc diffusion assay. The data from disc diffusion assay revealed that the effective NA concentration on both molds was 750 ppm. Some of dipping applications on both meat and cheese displayed promising results.Master Thesis Screening of Some Plant Species for Their Total Antioxidant and Antimicrobial Activities(Izmir Institute of Technology, 2008) Kaçar, Diren; Bayraktar, OğuzIn this study aqueous/ethanol extracts of 42 plant species collected from same geographic region (Karaburun/İzmir) were screened for their relative total phenol contents, total antioxidant and antibacterial activities. In the first part of the study, Folin- ciocalteu assay and PCL (Photochemiluminescence) method were performed to detect the total phenol contents and total antioxidant activities of extracts, respectively.It was detected that the Hypericum empetrifolium had the highest activities for both water soluble and lipid soluble antioxidants and Sarcopterium spinosum has the highest result for total phenol assay as 635.26 GAEqmg/g sample.In order to detect the antibacterial activities of extracts a preliminary screening study was performed by using disc diffusion method. Out of the 42 plant species tested, 26 species exhibited antibacterial activities by inhibiting one or more microorganisms.Microdilution assays by 96 well plates were applied for the most active species to find out their minimum inhibition concentrations (MICs). The most promising plant species in the study, having the antibacterial activities were determined as H. empetrifolium, P.terebinthus, Arbutus unedo, and C. parviflorus.In this study there is a clear relationship between the analysis results and S.spinosum is one of the most noteworthy species in this study showing the highest total phenol content and important biological activities which has never been examined scientifically before. In that manner this study also presents new potential species that can be used as natural raw materials in some related industries.Master Thesis Antimicrobial and Antioxidant Activities of Olive Leafextract and Its Food Applications(Izmir Institute of Technology, 2010) Aytul, Kerem Kaan; Korel, FigenIn this study, aqueous/ethanol extract of olive leaves (OLE) was examined for its antimicrobial and antioxidant activities and its possible food applications. In the first part of the study, relative antioxidant capacity and total phenol content of the extract were determined and found as 966 .g ascorbic acid eq./mg and 197.42 mg GAEq/g sample, respectively. In the second part, microdilution assays were conducted by 96 well plate for OLE to find minimum inhibition concentration (MIC) against Gram (+) and Gram (-) bacteria. The most susceptible bacteria were Escherichia coli, Listeria innocua and Staphylococcus carnosus. In the third part OLE was applied to raw beef cubes with 1%, 2% and 3% (v/w) concentrations to examine its antimicrobial and antioxidant effects. The results clearly indicated that usage of 2% and 3% OLE had the beneficial effect in controlling the microbial load, total viable and coliform counts, of beef cubes during 9 days of storage at 4 C. The 2% OLE treatment applied to beef cubes also delayed the oxidative deterioration compared to the other samples. As the last part of the study, 300 ppm OLE was applied to sardine (Sardina pilchardus) fillets as a marinade component. Results indicated that OLE was effective in controlling microbial load of sardine fillets and also delayed the oxidative deterioration and total volatile base nitrogen formation in the fillets during marination process.