Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Year-To Differentiation of Black Tea Through Spectroscopic and Chemometric Analysis(01. Izmir Institute of Technology, 2024) Yorulmaz, Hilal; Özen, Fatma BanuBu çalışmada, hasat yılının siyah çayın çeşitli spektral profilleri üzerindeki etkisi incelenerek, iki hasat yılından siyah çay örneklerinin ayırt edilmesi amaçlanmıştır. Her metodolojinin avantajlarından yararlanılarak, orta kızılötesi, UV-görünür ve floresan spektroskopisinin yetenekleri, çok değişkenli istatistiksel yöntemlerle birlikte kapsamlı bir şekilde incelenmiştir. Değişen iklim koşulları ve mevsimsel döngüler nedeniyle, çay gibi gıda ürünlerinin bileşimi bir hasat yılından diğerine daha değişken hale gelmiş ve genel ürün kalitesini etkilemiştir. Bu nedenle, 2021 ve 2022'de hasat edilen 205 çay örneğini incelemek için orta kızılötesi, UV-görünür ve floresan spektroskopisi kullanılmıştır. Orta kızılötesi spektrumlar hem demlenmiş hem de toz örnek formları için toplanırken, yalnızca demlenmiş örnekler diğer spektroskopik yöntemler kullanılarak analiz edilmiştir. Örnekleri hasat yılına göre sınıflandırmak için PLS-DA, OPLS-DA ve SIMCA modelleri geliştirilmiştir. Orta kızılötesi verilere dayanan modeller toz örnekler için %93,33 ve aşılanmış örnekler için %90,33 doğru sınıflandırma oranlarına ulaşmıştır. Ek olarak, floresan ve UV-görünür spektral veriler sırasıyla %98,3 ve %100 başarı oranlarıyla oldukça doğru sonuçlar vermiştir. SIMCA diğer çok değişkenli yöntemlerle karşılaştırıldığında daha düşük performans gösterse de bulgular spektroskopik tekniklerin kemometrik yaklaşımlarla entegre edilmesinin siyah çayı farklı yıllarda etkili bir şekilde izleyebileceğini böylece, çay üretiminde kalite kontrol ve sınıflandırma süreçlerinin iyileştirilmesine katkıda bulunabilir.Master Thesis Investigation of Antimicrobial, Antioxidant and Cytotoxic Properties of Some Green Leaf Plants(2023) Çetin, Elif Nur; Baysal, Ayşe Handan; Özen, Fatma BanuThe present study aims to investigate the chemical composition, antimicrobial activity, antioxidant properties, and cytotoxic activity of extracts obtained from leaf samples that are discarded as waste products. For this purpose, two different green leaves were selected: one is the grape (Vitis vinifera) leaf, a by-product from the winemaking process, and the other is the cauliflower (Brassica oleracea, var. botrytis) leaf, which is a waste product of cauliflower, and they were subjected to related tests. Both leaf samples were extracted by water because of its easy accessibility and environmentally friendly properties. Leaf extracts were examined according to their total phenolic content and subjected to chemical characterization by Liquid chromatography-quadrupole time-of-flight tandem mass spectrometry system. The promising antioxidant activities of the water-extracted leaf samples were authenticated through DPPH and ABTS assays. Antimicrobial and antibiofilm activities were examined against some Gram-positive (Bacillus cereus, Listeria innocua, and Carnobacterium divergens) and Gram-negative (Escherichia coli, Serratia liquefaciens, and Salmonella Typhimurium) strains, and two fungi (Saccharomyces cerevisiae and Candida albicans) species. Both tested leaf extracts showed a dose-dependent antimicrobial activity, while the antimicrobial activity of grape leaf extract was slightly higher. However, their activities against biofilm formation were varying in different bacterial and fungi species. The cytotoxic activity of the leaf extracts was examined on the mouse fibroblast cell (L929) line. According to the presented results, neither of the leaf extract samples used in the study showed any unwholesome effects on the cell line at any time point.Master Thesis Techno-Functional Properties of Bakery Products Containing Legume and Nut Flours(01. Izmir Institute of Technology, 2023) Doğruer, Ilgın; Özen, Fatma Banu; Özen, Fatma BanuThe purpose of this study is to develop nut and legume flour-based cookie formulations with improved functional properties and to investigate the rheological, spectroscopic, and technological characteristics of these products. In addition to sensory testing, the rheological, spectroscopic, and technological properties of cookies made with different ratios of double (combinations of chickpea-hazelnut and chickpea-carob flours) and triple composite flours (chickpea-hazelnut-carob flours) were assessed. The findings of the flour analyses show that the protein contents of raw and cooked chickpea flours are higher than wheat flour. Hazelnut flour stands out for having a high-fat content; 35 times higher compared to wheat flour, and 6 times as chickpea flour. Pre-cooked chickpea flour has a strong capacity to retain water when compared to the other flours used in the formulation of gluten-free cookies. Its capacity to hold water is about 3.5 times greater than that of wheat flour. The sample with 90% chickpea flour has the highest firmness (N) value and the greatest difference from the other formulations, according to the rheological properties. However, among all the samples, the dough with the highest hazelnut content (60%) gets the lowest firmness grade. In accordance with principal component analysis, all cookie dough samples that contain double and triple composite flours are grouped based on their formulations, and cookies that just contain chickpea flour are separated from the others. Moreover, it may be concluded from the sensory evaluation of the cookies that the inclusion of hazelnut and carob flour influences customer preferences favorably.Master Thesis Effects of Storage on Some Chemical Parameters of Olive Oils(Izmir Institute of Technology, 2019) Başak, Nagihan; Özen, Fatma Banu; Tokatlı, E.FigenMixing of fresh olive oil with olive oil from previous season is an emerging problem, and several chemical parameters have been proposed for the determination of this type of adulteration. The main objective of this study is to investigate the changes in several quality parameters (fatty acid alkyl esters, diacylglycerols and pigments) and spectral profiles of olive oils and olive oils adulterated with old olive oil as quality and authenticity indicators. For this purpose, fresh olive oil samples from North and South Aegean Regions and their blends with olive oil from previous year were stored for 15 months and changes in basic quality parameters (free fatty acidity, specific absorbances, fatty acids), fatty acid alkyl esters, diacylglycerol and pigment contents as well as ultraviolet-violet visible and mid-infrared spectral data were assessed to investigate effect of storage. Data were examined using multivariate analysis. Free fatty acid limit of extra-virgin olive oils was exceeded in 6 months for the samples mixed with old oil at concentrations of 30% and higher. The most significant changes during storage were observed in free fatty acidity, fatty acid alkyl ester and pigment composition of the olive oils. Spectral data and pigment composition provided the best separation with respect to storage periods. None of the parameters investigated provided clear results in terms of detection of adulteration.Master Thesis Effect of Deep-Frying on the Quality Parameters of Vegetable Oils(Izmir Institute of Technology, 2015) Avcı, Başak; Tokatlı, E.Figen; Özen, Fatma BanuIt was aimed to determine the changes in several chemical parameters, fatty acid composition and phenolic profiles of different types of olive oils (extra virgin, virgin, blended, refined) and sunflower oil in the deep-frying process. In addition, UV and FTIR spectroscopic data were collected during frying and they (UV, FTIR and the combination of FTIR and UV) were analyzed with multivariate statistical techniques (PCA, OPLS-DA and OPLS) to classify the oil samples and predict the chemical parameters. A domestic deep-fat electrical fryer was used to fry french fries for 4 minutes at 180ºC ten times without oil replenishment and oil samples were removed after 1st, 2nd, 3rd, 4th, 5th, 7th and 10th frying. Free fatty acid, peroxide value, K232, K270, total chloropyll and carotenoid contents, color, oxidative stability, total phenol content, total polar compounds, and fatty acid profiles of all oil samples and phenolics of extra virgin and virgin olive oils were determined. At the end of the tenth frying, no significant changes were detected in acidity, stability, and fatty acid compositions. Phenolic contents of extra virgin and virgin olive oils decreased after the fourth frying cycle. According to PCA and OPLS-DA results, UV spectra was able to discriminate oil samples. Chemical parameters, except peroxide value, were predicted with high accuracy by spectroscopic data. The fatty acids were predicted successfully with FTIR data, while the total phenol content was predicted by UV data with a higher R2 value. The combination of FTIR and UV spectra predicted the rest of the chemical measures in OPLS regression with a high accuracy.Master Thesis Chemical Characterization of Olive Oils From Karaburun Peninsula(Izmir Institute of Technology, 2014) Uncu, Oğuz; Özen, Fatma BanuChemical characteristics of olive oils produced from Erkence olive variety that is mainly grown around Karaburun Peninsula of İzmir have not been investigated thoroughly although this variety has high oil content and ripens earlier compared to other olive types. Identifying the chemical characteristics of olive oils could be useful to obtain geographical indication labelling for olive oils produced from this variety. Aim of this study is to determine some important chemical characteristics of olive oils from Erkence olive variety produced in Karaburun region and to investigate the differences in olive oils that come from various parts of the Peninsula using chemometric techniques as principal component analysis (PCA) and partial least square (PLS) regression. For this purpose, total phenolic content, fatty acid profile, phenolic profile, total carotene and chlorophyll contents and oxidative stability of 64 olive oils were determined. FTIR spectra for these oils were also evaluated. According to PCA results, classification with respect to geographical origin was relatively more successful with FTIR analysis while phenolic and fatty acid profiles did not result very satisfactory separation between regions. Moreover, FTIR spectra and various chemical parameters were used to predict oxidative stability of all olive oil samples. Oxidative stability was predicted successfully from IR spectra whereas prediction from chemical parameters was not that successful. IR spectra were also used to predict various chemical parameters. As a result of PLS regression; chlorophyll and carotenoid, some individual phenolic components (pcoumaric, hydroxtyrosol) and some major fatty acids (oleic, linoleic and palmitic) were predicted.Master Thesis Physical and Antimicrobial Properties of Biofilms Containing Natural Antimicrobial Agents(Izmir Institute of Technology, 2008) Türe, Hasan; Özen, Fatma BanuThe goal of this study is to evaluate physical and antimicrobial properties of biopolymers prepared from gluten (WG) and methyl cellulose (MC) with incorporation of activated lactoferrin (ALF), rosemary extract (RE) and natamycin (NA). The effectiveness of agents and antimicrobial films were investigated by agar disc diffusion method. Mechanical and water vapor permeability (WVP) of antimicrobial films were also examined. Film structure was investigated by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Application of films was studied on Kashar cheese inoculated with target molds during 30 days storage at 10oC.ALF and RE did not show inhibitory activity against tested microorganisms.Minimum inhibitory concentration (MIC) of NA was found 750 ppm against Aspergillus niger and Penicillium roquefortii. Both films containing NA showed antifungal activity concentrations at and above 2 and 1 mg NA/10 g film solution (fs) against A. niger and P. roquefortii, respectively. RE in combination with NA reduced MIC of NA against A. niger to 1.5 mg NA/10g fs in both films. FTIR spectroscopy did not indicate any interaction between NA and both films. SEM observations showed that NA crystallizes at high concentrations in biopolymers. There was no significant change in WVP of films containing NA. Incorporation of NA to WG film did not cause major changes in its mechanical properties. Reduction in tensile strength of MC films was observed at high NA concentration. Application studies demonstrated the efficacy of WG and MC films including NA against A. niger and P.roquefortii inoculated on Kashar cheese.Master Thesis Chemical Characterization of 'hurma Olive Grown in Karaburun Peninsula(Izmir Institute of Technology, 2013) Aktaş, Ayşe Burcu; Özen, Fatma BanuOlive type, mostly Erkence, grown in nearby area around Karaburun peninsula of Izmir-Turkey, goes through a natural debittering phase on the tree during its ripening. This olive is known by the name of Hurma and loses its bitter taste while still on the tree and can be consumed directly at the end of this natural process. The aim of this study is to investigate the changes in the chemical composition of Hurma, Erkence and Gemlik olives throughout their maturation period and to determine some chemical compositional differences between Hurma and other types of olives to obtain more insight about the natural debittering phenomena. For this purpose, the chemical parameters measured are pH, water activity, total fat amount, fatty acids, sugar and organic acid amounts, total phenol content and phenol profile. All analyses were performed for two harvest years. Data were analyzed by ANOVA and principal component analysis (PCA) to investigate the differences regarding the olive types, ripening period and harvest year. Total phenol content and generally concentration of individual phenolic compounds of Hurma olive were lower than Erkence and Gemlik olives. Both fatty acid and phenol profiles allowed a differentiation with respect to type and also harvest year according to PCA while organic acid and sugars provided a separation only in terms of harvest year.Master Thesis Bioethanol Production From Fungal Sources Using Low-Cost Agro-Industrial Waste Products(Izmir Institute of Technology, 2012) Evcan, Ezgi; Tarı, Canan; Özen, Fatma BanuIn recent years, the rapid increase in environmental problems, greenhouse gas emissions, fuel prices and the unlimited consumption of fuel stocks made people search for some alternative energy sources. Bioethanol is one of the most popular alternative sources with its many beneficial features. Considering the sugar content of fruit pomaces, which are the waste of fruit juice industry, are very convenient and cheap fermentation raw materials for production of bioethanol. The aim of this study was to create a renewable alternative for fossil fuel and to provide a viable solution to multiple environmental problems simultaneously creating a sink for waste utilization and optimize bioethanol production from apple pomace hydrolysate using Trichoderma harzianum, Aspergillus sojae and Saccharomyces cerevisiae by statistical methods. Here, screening and optimization steps were conducted in order to determine the significant factors and their optimum levels. Factors such as inoculation rate of A.sojae and T.harzianum and agitation speed were considered as factor variables, whereas the response variable was bioethanol production. According to the results of the screening process, inoculation rate of S.cerevisiae was fixed as 4% and aeration method as vented. In the optimization step, levels of the other factors were enlarged. The highest bioethanol production and yield on substrate were 8.748 g/l and 0.946, respectively. Higher concentrations of inoculation rates of T.harzianum and A.sojae (6%) and agitation speed of 200 rpm led to maximum bioethanol production. Furthermore, the results pointed out that using cocultures because of its synergistic interactions is an effective way for production of bioethanol.Master Thesis Varietal Classification and Prediction of Chemical Parameters of Turkish Wines by in Frared Spectroscopy(Izmir Institute of Technology, 2010) Öztürk, Burcu; Özen, Fatma Banu; Özen, Fatma BanuThis study was performed with the aim of varietal classification of mono-varietal Turkish wines and development of models to predict basic enological parameters from mid-IR spectra with the use of chemometric methods. Mid-infrared (MIR) spectroscopy combined with multivariate data analysis was employed to make a varietal classification of commercial Turkish wines (Boğazkere, Cabarnet Sauvignon, Çalkarası, Kalecik Karası, Merlot, Öküzgözü, Papazkarası, Shiraz, Emir, Misket, Narince, Sultaniye and Chardonnay) from 2006 and 2007 vintages. Wine samples (n.79) including red, rose and white wines were scanned in the mid-IR region (4000-650 cm-1) and three spectral regions (965-1565 cm-1, 1700-1900 cm-1 and 2800-3040 cm-1) were used to classify wines on the basis of grape variety. The principal component analysis (PCA) was applied to the spectral data of the wine samples. Although a clear classification could not be achieved according to varieties, almost complete classification of red and white wines was observed. For the quantification analysis, a total of eleven enological parameters, including total phenol and anthocyanin content, pH, brix, titratable acidity, colour intensity (CI), tint, yellow%, red%, blue% and the proportion of red colour produced by anthocyanins (dA%) were determined with analytical reference methods. Correlation between the results of the reference methods and MIR spectral data was tested with partial least square (PLS) regression analysis and prediction models were developed with the use of these correlations. The calibration and validation sets were established to evaluate the predictive ability of the models. As a result of PLS analysis, the best models were developed for total phenols and CI with excellent predictions (R2.0.93 and 0.89, respectively and residual predictive deviation RPD.3.68 and 3.83, respectively). The model of pH determination and yellow% gave a good prediction (R2.0.85 and 0.85, respectively and RPD.2.7 and 2.04, respectively).