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Fabrication of Colorimetric Ph Indicator Films by Electrospinning
(Izmir Institute of Technology, 2022) Eroğlu, Ahmet Emin; Bayramoğlu, Beste; Bayramoğlu, Beste; Eroğlu, Ahmet Emin; 03.08. Department of Food Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
The trend in the food packaging industry evolves towards innovative packaging materials as biosensors, which record the status of the product and can warn the consumer. The logic behind the colorimetric pH biosensor is that they provide the essential information about food visually by detecting change in pH. Anthocyanins are natural color pigments susceptible to pH change. Purple basil is rich in anthocyanins. In this study, ultrasound-assisted extraction was used for the extraction of dry purple basil. The processing conditions were optimized by response surface methodology (RSM) in terms of the total monomeric anthocyanin content and the increase in green intensity with pH. Electrospinning is a nanofiber fabrication operation used to encapsulate sensitive bioactive compounds for the production of intelligent sensing system. Polycaprolactone (PCL) films incorporating different purple basil extract (PBE) concentrations were fabricated by electrospinning procedure for the usage of colorimetric pH-indicator films as intelligent packaging. The most beadles and uniform nanofibrous mats were obtained when the spinning conditions were V=20 kV and Q=0.4 mL h-1for 10% (w v-1) PCLsolutions containing 0.4% and 0.6% (w v-1) PBE. The average fiber diameters in these films were 178.59±52.92 nm and 235.39±92.46 nm, respectively. The films gave promising results with regards to their use as colorimetric pH-indicator films. The time required to observe a visible color change (ΔE) in these films was only 4-5 s. The ΔE values between all successive pH’s were higher than 2, which is detectable by an inexperienced observer. Keywords: Anthocyanin, Purple Basil, Ultrasound-Assisted Extraction, Response Surface Methodology (RSM), Electrospinning, Colorimetric pH-indicator Films.
Structure and Gas Transmission Properties of Surface Modified Food Packaging Materials by Layer-By Assembly
(Izmir Institute of Technology, 2019) Koca, Nazan; Bayramoğlu, Beste; Bayramoğlu, Beste; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
In this study, two different LbL coatings of chicken egg white lysozyme (LZ) (0.2 % w/v)-gum arabic (GA) (0.2 % w/v) and lysozyme (LZ) (0.2 % w/v)-iota carrageenan (IC) (0.2 % w/v) were investigated as a potential agent in the fabricaton of surfacemodified food packaging materials with improved gas barrier properties. The effects of solution pH, adsorption time, number of layers, and inclusion of drying step in between deposition steps on multilayer formation were explored for both LbL coatings seperately. Film growth was monitored up to 10 layers by UV-Vis spectrometry and Surface Plasmon Resonance (SPR), which allows for in situ observation of the multilayer formation. The LbL coatings were characterized by AFM (Atomic Force Microscopy) and SEM (Scanning Electron Microscopy). The oxygen and water vapor transmission rates of the coatings (assembled on corona treated polypropylene (PP) films) were also measured. The most successful LbL assembly was obtained at pH 7-7 combination, with 20 minutes adsorption time and with intermediate drying steps for both (LZ-GA and LZ-IC) LbL coatings. For both LbL coating, both the UV-Vis and SPR measurements showed the similar zig-zag trend; i.e. desorption of some of the pre-adsorbed LZ from the interface with the deposition of GA (or IC) on it, probably due to formation of soluble complexes between them. The importance of intermediate drying steps was established by UV-Vis, AFM and gas transmission rate measurements. The absence of intermediate drying caused a reduction in total mass deposited and the gas barrier properties of the coatings.
Comparison of Dipping and Spraying Methods in Layer-By Deposition of Chitosan and Sodium Caseinate
(Izmir Institute of Technology, 2016) Üney, Sinem; Bayramoğlu, Beste; Bayramoğlu, Beste; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
In this thesis; it is aimed to develop a novel, ultra thin, homogeneous edible coating with adequate gas barrier properties by layered deposition of chitosan and sodium caseinate with dipping and spraying methods and compare the coating structures. The parameters considered in this study are pH, adsorption times, number of layers and the types of the top layer. To determine the appropriate conditions, zeta potential and hydrodynamic diameter measurements of chitosan and sodium caseinate were done. After determining the appropriate concentrations and pH values, layer deposition has been initiated. Following the formation of multilayer coating by UV-Vis spectrophotometer, the most suitable combination was determined for the formation of multilayer coating. Multilayered coating characterization was done by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Surface Plasmon Resonance which allows to observe coating formation in-situ. Moreover antimicrobial activity, water vapor permeability and oxygen permeability were also investigated. It has been observed that the multilayer coating structures obtained by dipping and spraying methods have some differences. The formation of multilayer coating has been followed successfully with UV-Vis spectrophotometer; besides information about surface topography and coating thickness is obtained by Atomic Force Microscopy (AFM). The multilayered coatings have no significant effects on oxygen permeability and water vapor permeability; however it has contact antimicrobial effect.

Master Degree / Yüksek Lisans Tezleri

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