Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
8 results
Search Results
Master Thesis Development of Molecular Fluorescence Spectroscopy Based Multivariate Calibration Models for Quantitative Determination of Fatty Acids and Triacylglycerol Compositions of Olive Oils(01. Izmir Institute of Technology, 2020) Hedef, Onur; Özdemir, DurmuşThis study illustrates the quantitative determination of fatty acid and triacylglycerol composition of olive oils by using multivariate calibration methods namely partial least squares (PLS) and genetic inverse least squares (GILS) coupled with molecular fluorescence spectroscopy. The reference analysis of the olive oils was carried out with gas chromatography (GC) and high-performance liquid chromatography (HPLC) for the compositions, respectively. A total of 125 olive oil samples were collected from Marmara and Aegean olive growing regions in western Turkey, right after the olives oils are produced in the 2010 -2011 season. Chromatographic and fluorescence analyses were performed simultaneously on the samples and then collected spectra were combined with reference analysis results for the multivariate calibration step. Among the several components analyzed by both GC and HPLC, 10 components from fatty acids and 10 components from triacylglycerols were chosen for modeling. Multivariate calibration models were constructed by randomly selecting 100 samples as calibration set and assigning the remaining 25 samples to the independent validation set using PLS and GILS with leave one out cross-validation based on the fluorescence spectra of the olive oils. The results have demonstrated that the compositions could be successfully determined by using molecular fluorescence spectroscopy. The standard error of cross-validation (SECV) and standard error of prediction (SEP) values were acceptable for most of the components. The regression coefficients (R2) of reference values vs. predicted values ranged from 0.70 to 0.98, indicating that molecular fluorescence spectroscopy combined with multivariate calibration could potentially be used for quantitative determination.Master Thesis Assesment of Genes That Play Role in Phenolic Compound Degradation in Olive Orchard Microbiome(Izmir Institute of Technology, 2019) Acar, Ertuğrul; Soyer Dönmez, FerdaThe olive tree (Olea Europea L.) is one of the most important fruit trees in Mediterranean countries. Its products, olive oil and table olives, are important components of the Mediterranean diet and widely consumed all around the World. Olives and virgin oil provide a rich source for phenolic compounds. The plant phenolics are secondary metabolites, and possesses several common biological and chemical properties. In this study, microorganisms were collected from soil, olive leaves, fruits, and Olive fruit fly larva and Olive mill wastewater (OMWW). They were characterized by 16S rRNA analysis. The microorganisms that were tolerant to phenolic compounds were selected in order to seek which genes were associated with the phenolic compound degradation. The genes related to the degradation of the selected organisms were identified by Sanger Sequencing and the level of phenol-degrading gene expression were aimed to be compared by using qPCR and Droplet Digital PCR (ddPCR). Microorganisms which degrade phenolic compounds can be harnessed for the purpose of bioremediation. However, the number of defined phenolic compound degrading microorganisms is still low in the literature. For this reason, many different microorganisms were used at the same time for bioremediation. Investigation of olive orchard microorganisms and phenolic-degrading genes might benefit bioremediation in the future. In this study, 8 different bacterial strains were identified and characterized from olive orchards. After that, their phenol hydroxylase and catechol 1,2 dioxygenase genes tried to be sequenced with primers designed by using of reference strains in NCBI database.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 Development of Molecular Spectroscopic Multivariate Calibration Models for the Determination of Fatty Acid and Triachyl Glycerol Compositions of Olive Oils(Izmir Institute of Technology, 2014) Kuday, Esra; Özdemir, DurmuşThe determination of fatty acid methyl esters and triachyl glycerol compositions of olive oils by chromatographic methods require not only sample pre treatment carried out but also extend the time of the analysis. Also, chromatographic methods are expensive. Therefore, there is a need for an alternative method. In this study, it is aimed to develop molecular spectroscopic multivariate calibration models for the determination of some of the fatty acid methyl esters and triachyl glycerol compositions of olive oils. For this purpose, 79 olive oil samples from different regions of Turkey (Manisa and Bursa) were collected and scanned with Fourier Transform Infrared spectroscopy equipped with attenuated total reflectance (FTIR-ATR) accessory, Fourier Transform Near Infrared spectroscopy (FTNIR) and Gas Chromatography (GC), High Performance Liquid Chromatography (HPLC). Chromatographic analyses of these samples were done by Olive Oil Research Institute and spectroscopic analyses were done by our group. The data obtained from High Performance Liquid Chromatography (HPLC) was chosen as a reference method for triachyl glycerol compositions and also the data obtained from Gas Chromatography (GC) was chosen as a reference method for fatty acid methyl esters. Also, Genetic inverse least squares (GILS) and Partial least square methods (PLS) were used for multivariate calibration. In conclusion, NIR and FTIR combined with multivariate calibration models can be more advantageous compare to chromatographic methods because of their simplicity and speed. When investigating the results, relatively successful calibration models were obtained from GILS method than PLS method.Master Thesis Effect of Storage Time on Olive Oil Quality(Izmir Institute of Technology, 2009) Yıldırım, Gaye; Tokatlı, FigenThis work reports changes in the major quality parameters of Turkish extra virgin olive oils stored at room and refrigerator temperatures in dark and monitored for 14 months. Peroxide values, specific absorbance values, total phenol content, free fatty acidity, fatty acid and phenolic profiles of extracted (Erkence and Ayvalık-Edremit) and commercial extra virgin olive oil samples (Altınoluk, Ezine, Bayındır and Ortaklar) from South and North of the Aegean were determined. The acidity and K232 values of samples were within the acceptable limits, the peroxide and K270 values exceeded the limits after 7 and 9 months storage. Hydroxytyrosol, tyrosol, caffeic acid, vanillic acid, vanilin, p-coumaric acid, ferulic acid, m-coumaric acid, cinnamic acid, luteolin, and apigenin were determined as the major phenolics in Turkish extra virgin olive oils. The concentration of hydroxytyrosol and tyrosol increased, while a decrease was observed in the amounts of other phenolics during storage.The highly unsaturated flaxseed oil was mixed with olive oil at 5-15 % levels and stored at room and refrigerator temperature to examine the effect of olive oil on the oxidative stability of flaxseed oil. 15% olive oil addition to flaxseed oil increased its oxidative stability. Fourier Transform (FT-IR) spectral data were used to predict the oxidative quality parameters, total phenol content and the fatty acid compositions by partial least square analysis (PLS). FT-IR spectra of samples subjected to accelerated oxidation were examined to determine the bandwidths, which can be considered as the finger-prints of the oxidation phenomenon (2924, 2852, 1746-1743, 1163 and 967-976 cm-1).Master Thesis Antimicrobial and Antioxidant Activities of Turkish Extra Virgin Olive Oil From Different Varieties(Izmir Institute of Technology, 2009) Karaosmanoğlu, Hande; Soyer Dönmez, FerdaOlive oil is the main source of fat in Mediterranean diet. The major active components of olive oil include oleic acid, phenolic compounds and squalene which have different benefits such as cancer prevention, antimicrobial and antioxidant activities, and lowering the incidence of skin cancer, respectively. In recent years, the number of studies about the biochemical properties of different varieties of olive oils and their phenolic contents has dramatically increased.In this study, Turkish EVOO from different varieties and their phenolic compounds were investigated in terms of their antimicrobial and antioxidant properties as well as refined olive, hazelnut and canola oils. Antimicrobial activities of EVOOs and ten phenolic compounds were tested against three foodborne pathogenic bacteria, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Enteritidis which are the foremost bacterial cause of the largest number of outbreaks, cases and deaths in the world. While all EVOOs showed bactericidal effect the phenolics demonstrated slight antimicrobial activity with percent inhibition between 0-25 of growth rate of bacteria. Moreover, refined olive, hazelnut and canola oils did not show any antimicrobial activity.Finally, antioxidant activities of EVOOs, refined olive, hazelnut and canola oils were determined by B-carotene-linoleic acid model system and ABTS radical scavenging method. According to B-carotene-linoleic acid method, it was observed that antioxidant activities of oil samples varied between 21.19% and 64.54%. On the other hand, it was found that free radical scavenging activities varied between 1.21% and 21.97% as a result of ABTS method. These results were correlated with TPC values of oils.