Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Bio-Based Coatings as Flexible Food Packaging Applications(Izmir Institute of Technology, 2018) Adalı, Merve Betül; Korel, FigenThe sustainable packaging solutions require the development of materials based on renewable resources and efficient production methods, which are important nowadays. In this study, a multilayer coated flexible polyethylene terephthalate (PET) sheets were produced by Layer-by-Layer (LbL) assembly using chitosan and pectin bio-based materials incorporated with galls extract (GE) as an active agent. These fabricated films were firstly characterized and results of increasing the depositing of chitosan and pectin from 0 to 60 layers indicated that the deposition of biopolymers successfully improve the performance of flexible films. The optimization of the deposition different number of layer on PET (20 – 40 and 60 layers) was carried out by the study of the surface characterization and the shelf-life tests in order to find out surface modification. The coated LbL films were applied on fresh-cut ‘Abate Fetel’ pears and color, microbial, sensory assays were carried out during 7 days of storage at 4 ºC. At the end of storage, in terms of all tests, the LbL treated samples were presented better preserved compared to the control samples (treated base film). In addition, the release of active agents from multilayer films was evaluated using LbL films in contact with food and gradual reduction was observed. This research demonstrates the feasibility of LbL coating, which acts as a carrier of active substances to enhance the quality of fresh-cut products as an active packaging system.Master Thesis Development of a Novel Active Packaging System Based on Layer-Sy Layer Deposition of Natural Antioxidants and Antimicrobials To Extend Food Products' Shelf Life(Izmir Institute of Technology, 2017) Akgün, Begüm; Korel, FigenIn recent years, Layer-by-Layer (LbL) assembly of thin films has been extensively investigated for many purposes, particularly for its functionality and simplicity of fabrication. Through LbL assembly; antioxidant agents have beenincorporated into active packaging systems in different forms, mainly including sachets, physical adsorption on packaging material surface, multilayer films which contact with food packaging surface. In previous studies, active packaging systen associated with LbL depositions were investigated, but no detailed investigation has been found about the application of controlled releasing-active packaging system on fresh-cut fruits. In this study, 20 bilayers of chitosan and alginate; respectively; were coated on amorphous polyethylene terephthalate (A-PET) sheets by dipping method. The LbL treated PET films were used for active packaging of fresh-cut peaches. Total soluble solids content and titrable acidity demonstrated that LbL active coating did not interfere with the natural postharvest behaviour. A lower weight loss was observed for LbL coated peach saples, suggesting that the presence of layer structure on PET strips could act as a barrier against fruit water loos. After 7 days of storage, the LbL treated samples have shown the best preservation of carotenoids, the lower PPO activity and higher phenolic index. Microbiological analysis has shown that all the microbiological analysis has that all the microorganism types which were invetigated were affected by the actice packaging system.Sensory results were really encouraging, as well. As a conclusion, LbL coating has been proved for being a useful technique to produce controlled-release active packaging systems on fresh-cut fruits.Master Thesis Effects of Preharvest and Postharvest Treatments on Quality Characteristics of Grapes(Izmir Institute of Technology, 2016) Konuk, Dilara; Korel, FigenGray mold, caused by Botrytis cinerea, is the most important disease which causes major quality and quantity losses in preharvest period and postharvest storage of grapes. Grapes are commonly treated with sulfurdioxide (SO2) to control decay caused by Botrytis cinerea both in vineyard and during storage. However, there is need for natural alternatives to replace SO2 because of many considerations related with sulfite residues, emergence of B.cinerea resistant strains, hazards for human and environment, negative effects on quality characteristics and sustainability, and certification for organic grapes. In this study, the effects of alginate solution with or without (w/wo) vanillin as preharvest spray and postharvest edible coating on quality, safety and biochemical properties of grapes from Semillon Blanc, Alphonse Lavalleé and Razaki cultivars were investigated. Soluble solid content, pH, titratable acidity, total phenolic content, antioxidant activity, yeast-mold counts, lactic acid content, color, and firmness were determined at the day of preharvest treatment, at harvest and during 35 days of storage at 4±2°C. In addition, sensory evaluation of grapes coated w/wo vanillin were also performed using hedonic scale test. Alginate treatments w/wo vanillin were effective in preventing weight, soluble solids, acidity, and firmness losses. Incorporation of vanillin into alginate coating provided significant reduction in yeast-mold growth. Moreover, phenolic content and antioxidant activity of grapes treated with alginate coating incorporating vanillin were higher than others during postharvest storage. In sensory evaluation, appearance was ranked as the highest for alginate coating wo vanillin. As a conclusion, alginate solution enriched with vanillin could be a natural alternative of synthetic fungicides to prevent deteriorations and enhance quality of grapes.Master Thesis Effects of Olive Variety, Harvest Time, and Malaxation Temperature on Volatile Compounds and Sensorial Characteristics of Olive Oils(Izmir Institute of Technology, 2015) Yıldız, Gamze; Korel, FigenIn this study, it was aimed to determine the differences between sensory properties of olive oils based on types of olives, malaxation temperature and harvest time. Olive oil samples were extracted from two different Turkish olive cultivars (Ayvalık and Memecik), provided by Tariş Olive and Olive Oil Agricultural Sales Cooperatives Union. Olives which were harvested at three different stages of ripening (early (first harvest time), mid (second harvest time) and late (third harvest time)) were extracted at three different malaxation temperatures (27°C, 37°C, 47°C). Samples were classified into eighteen groups by two olive varieties, by three harvest time and malaxation temperatures. Totally, 36 samples (18 treatments × 2 replicates) were obtained from two parallel extraction processes. The effects of cultivar, malaxation temperature and harvest time on volatile composition, sensory properties and color of olive oils were investigated. SIMCA 13.0.3 (Umetrics AB, Umeå, Sweden) and multilevel factorial experimental design were used for data analysis and result interpretation. As a conclusion, it was found that cultivar and harvest time of olives had a significant effect on sensorial characteristics of olive oils. However, no obvious effect of malaxation temperature was observed.Master Thesis Mechanical and Gas Permeability Properties of Nanocomposite Films Made From Low Density Polyethylene and Carbon Nanotubes(Izmir Institute of Technology, 2014) Anggoro, Bayu Meta; Korel, FigenIt is important to develop new food packaging materials with enhanced properties. In this work, nanocompositewas prepared by melt blending linear low density polyethylene (LLDPE) and multiwalled carbon nanotubes (MWCNT) by using twin-screw extruder, then hot-pressing was applied to produce nanocomposite films. The effect of the addition of three different dimensions of MWCNT on the mechanical and gas permeabilities properties was investigated, along with overall migration. According to the film characterization results by scanning electron microscopy, the dispersion of MWCNT in general was considerably average. The presence of interaction networks between LLDPE–MWCNT was observed, so did the presence of carbon nanotubes agglomerations. Relatively better dispersion was achieved by the nanocomposite films containing 0.25 wt. % MWCNT at any dimension. It was observed that the dispersion of carbon nanotubes corresponded with the improvement in mechanical and gas barrier properties. The consistent improvement was shown in Young‘s modulus with the increment up to 26.9 % as the content of MWCNT increased. Moreover, the addition of MWCNT could enhance the gas barrier properties by lowering the gas permeabilities up to 26.5 % and 32 % for oxygen and carbondioxide, respectively. The results from mechanical properties and gas permeabilities revealed that the content of MWCNT was more crucial to affect the improvement rather that its dimension. In terms of overall migration, the results were found below the limit required by European Union Commission (10 mg/dm2). Considering these outstanding results, the developed material could be applied in food packaging, particularly in active packaging system.Master Thesis Antimicrobial Properties of Silk Fibroin-Carrageenan Films Incorporating Grape Seed Extract(Izmir Institute of Technology, 2009) Arserim Uçar, Dilhun Keriman; Korel, FigenIn this study antimicrobial edible films were developed by incorporation of grape seed extract into silk fibroin-carrageenan films. Developed films were subjected to instrumental analysis such as scanning electron microscopy, atomic force microscopy, X-ray diffractometer, and Fourier transform infrared spectrometer for the characterization of the film. The antimicrobial activity of silk fibroin-carrageenan films on different bacteria including Listeria innocua, Staphylococcus aureus, Staphylococcus carnasus, Bacillus amyloliquefaciens, Escherichia coli, Pseudomonas fluorescens, Escherichia coli O157:H7, and Salmonella Typhimurium, on raw chicken breast meat and beef sausages were tested. Application of silk fibroin-carrageenan films incorporating grape seed extract and/or Na2EDTA on chicken breast meat and beef sausages demonstrated the efficacy of these films to enhance the microbial quality of the products. Increasing the concentration of grape seed extract in the films increased the antimicrobial activity of the films in food applications. It is found that silk fibroin-carrageenan films incorporating grape seed extract could be used to control the growth of S. aureus on beef sausages during 28 days of storage at 4 C. The use of these films on beef sausages had significant effect on moisture content of the sausages as well as the textural properties of the sausages. This study indicated the potential of using silk fibroin-carrageenan films incorporating grape seed extract to be used as an antimicrobial edible food packaging.Master Thesis Classification of Virgin Olive Oils From Different Olive Varieties and Geographical Regions by Electronic Nose and Detection of Adulteration(Izmir Institute of Technology, 2008) Kadiroğlu, Pınar; Korel, FigenExtra virgin olive oils produced from fresh and healthy olive fruits have a delicate and unique flavor that makes them highly appreciated by consumers. Their taste and aroma are closely related to volatile and non-volatile compounds and determined by chromatographic and sensory analyses. However, these methods are expensive and time consuming to be used routinely in food industry. Electronic nose that can mimic the human sense of smell and provide low-cost and rapid sensory information is a new approach allowing the discrimination of aroma fingerprints of oils. In this study, the aroma fingerprints of Turkish extra virgin olive oils produced from various olive varieties (Ayvalık, Gemlik, Memecik, Erkence, Domat and Nizip) and Ayvalık and Gemlik olive varieties growing in two different regions of West Turkey (İzmir and Edremit) and the commercial extra virgin olive oils obtained from Tariş Olive and Olive Oil Agricultural Sales Cooperatives Union during two consecutive harvest years were determined by an electronic nose. In addition, the electronic nose was proposed for the detection of adulteration of these oils with monovarietal olive oils and with other edible oils such as sunflower, corn, soybean and hazelnut oils. The data were analyzed using chemometric methods by soft independent modeling of class analogy (SIMCA) software. As a conclusion, it was found that the electronic nose could provide good separation on some of the varieties and geographical regions. The electronic nose has been able to differentiate adulterated and non-adulterated extra virgin olive oils at higher than 10 % adulteration level successfully.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 Determination of Aroma Compounds and Exopolysaccharides Formation by Lactic Acid Bacteri Isolated From Traditional Yogurts(Izmir Institute of Technology, 2007) Çelik, Elif Sinem; Korel, FigenYogurt, consumed widely around the world, is a fermented milk product as a result of the lactic acid fermentation by addition of starter cultures containing Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. The most important criteria for yogurt production is the selection of starter cultures since each culture affects the end-product quality differently. Our natural flora and traditional flavor have been continously changing due to the introduction of imported commercial starter cultures. Because of the necessity to preserve our natural starter cultures and to increase the availability of them for industrial use, these cultures must be isolated from artisanal yogurts, genetically characterized and investigated regarding their technological properties. Aims of our study were to determine the technological and organoleptic properties of starter cultures previously isolated and genetically characterized and to assess the feasibility of near-infrared (NIR) spectroscopy for determining the yogurt quality.Total of 20 different yogurt samples were produced using combinations of 5 Streptococcus thermophilus and 4 Lactobacillus delbrueckii ssp. bulgaricus strains. Yogurt samples were stored at 4 °C for 21 days. Chemical, physical, microbial and organoleptic analyses for samples were conducted at predetermined days.As a conclusion, it was found that 4 Streptococcus thermophilus and 4 Lactobacillus delbrueckii ssp. bulgaricus yogurt isolates have potential to be used in dairy industry regarding their high technological and organoleptic characteristics. In addition, NIR spectroscopy technique could be used successfully on yogurt samples to predict total solids, fat, pH, syneresis, and microbial counts of yogurts based on the calibration models (Genetic Algoritm).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.