Izmir Institute of Technology

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Acoustic indoor localization employing code division multiple access
(Izmir Institute of Technology, 2010) Sertatıl, Cem; Altınkaya, Mustafa Aziz
Indoor localization becomes a demand that comes into prominence day by day. Although extensively used outdoor location systems have been proposed, they can not operate in indoor applications. Hence new investigations have been carried on for accurate indoor localization in the last decade. In this thesis, a new indoor location system, that aims to locate an entity within an accuracy of about 2 cm using ordinary and inexpensive off-the-shelf devices, has been proposed and an implementation has been applied to evaluate the system performance. Therefore, time of arrival measurements of acoustic signals, which are binary phase shift keying modulated Gold code sequences using direct sequence spread spectrum technique, are done. Direct sequence-code division multiple access is applied to perform simultaneous accurate distance measurements and provides immunity to noise and interference. Two methods have been proposed for the location estimation. The first method takes the average of four location estimates obtained by trilateration technique. In the second method, only a single robust position estimate is obtained using three distances while the least reliable fourth distance measurement is not taken into account. The system performance is evaluated at positions from two height levels using two sets of variables determined by experimental results. The precision distributions in the work area and the precision versus accuracy plots depict the system performance for different sets of variables. The proposed system provides location estimates of better than 2 cm accuracy within 99% precision. Eventually, created graphical user interface provides a user friendly environment to adjust the parameters.
Analysing the encrypted search algorithms on encrypted data
(Izmir Institute of Technology, 2018-07) Tekin, Leyla; Şahin, Serap
In this thesis, we study the static and dynamic Searchable Symmetric Encryption (SSE) schemes (Cash et al. (2014), Kamara and Moataz (2017)). We present different approaches for secure single- and multi-keyword ranked searches, that are: Sorted, OPEBased, Paillier-Based, Embedded, and Matrix-Based. We extend the base schemes according to these approaches so that the matching documents of a search query are ranked by a relevance score calculation technique like term frequency (tf), term frequency-inverse document frequency (tf-idf) or keyword frequency, depending on the characteristics of the scheme. For this, the existing structures of the schemes are modified since they cannot be directly used for ranked searches. Therefore, the ranking facility is added to them. Further, Matrix-Based Approach is a new hybrid approach that is based on an updated structure of the static scheme (Cash et al. (2014)) and fills a matrix to rank the relevant documents for a search keyword, as in the work (Ibrahim et al. (2012)), however, computing the matrix is totally different from their work.
Antimicrobial, antioxidant properties and chemical composition of some spices/herbs
(Izmir Institute of Technology, 2013-12) Yavuzdurmaz, Hatice; Baysal, Ayşe Handan
The present study aims to investigate the chemical composition, antimicrobial activity, and mechanism of antimicrobial activity, antioxidant properties of essential oils and extracts and the effects of them when applied to minced beef samples. For this purposes; four essential oils (bay leaf, thyme, clove and cumin), two extracts (grape seed and olive leaf) and constituents of essential oils (eucalyptol, linalool, α-terpineol and α-pinene) were subjected to related tests. Chemical characterization was complemented for all essential oils and extracts. Antimicrobial activity was examined against Staphylococcus aureus, Escherichia coli O157:H7, Salmonella Typhimurium, Listeria innocua, Shewanella putrefaciens, Carnobacterium divergens and Serratia liquefaciens. All tested compounds were effective on the bacteria with different concentrations. Antioxidant activity was proved by FRAP and DPPH methods. Physical disturbance and changes in the structures of bacteria was demonstrated by various techniques. The activity of two most potent essential oils (thyme and clove) was investigated in the minced meat application study. The findings represented that clove essential oil restricted the growth of S. Typhimurium and coliform bacteria. They did not have a significant inhibition effect on the aerobic mesophilic bacteria, total yeasts and molds and also psychrotrophic organisms. The results indicated that L* and a* values were maintained during the storage period. The featured effect of essential oils was antioxidant characteristic in meat application study. All treatment showed significant reduction in oxidation comparing with control. The obtained results may suggest that tested essential oils possess compounds with antimicrobial characteristic as well as antioxidant activity and therefore they can be used as natural preservatives in food especially in meat products.
Applications of mid-IR spectroscopy for identification of wine and olive yeasts and characterization of antimicrobial activities of phenolics on yeasts
(Izmir Institute of Technology, 2015-12) Canal, Canan; Özen, Fatma Banu; Baysal, Ayşe Handan
The aim of this study was application of mid-IR spectroscopy in combination with multivariate statistical analysis for characterization of yeasts from two fermented products, wine and olive, in comparison with cultural and molecular tests and characterization of antimicrobial effects induced by olive phenolics on yeasts. Totally 19 wine yeasts were molecularly identified as M. pulcherrima (11%), P. membranifaciens (16%), H. uvarum (5%) and S. cerevisiae (68%). According to FTIR spectroscopic data of wine samples, S. cerevisiae isolates formed a cluster which were generally separated from all other yeasts. Totally 182 olive yeasts were identified from naturally debittered Hurma and a common olive variety and their leaves. The most common yeasts were Metschnikowia sp. (39%) and Aureobasidium sp (78%) in the first and the second harvest years, respectively. Since only Aureobasidium sp. was the common yeast isolated from Hurma during both years, any link between natural debittering of Hurma and the yeast population of this olive type might be related to Aureobasidium sp. Molecularly identified yeast types generally formed different clusters and showed spectral differences. For antimicrobial activity tests, all phenolic compounds were found effective on both S. cerevisiae and A. pullulans; however, A. pullulans was observed to be more sensitive. Antimicrobial activity was differentiated with respect to treatment time and phenol concentration with statistical treatment of FTIR data. As a complementary technique, FTIR could be successfully used for identification of yeasts and characterization of antimicrobial activity of phenolics against yeasts.
Artificial neural networks model for air quality in the region of Izmir
(Izmir Institute of Technology, 2002) Birgili, Savaş; Tayfur, Gökmen
In this study, a systematic approach to the development of the artificial neural networks based forecasting model is presented. S02, and dust values are predicted with different topologies, inputs and transfer functions. Temperature and wind speed values are used as input parameters for the models. The back-propagation learning algorithm is used to train the networks. R 2 (correlation coefficient), and daily average errors are employed to investigate the accuracy of the networks. MATLAB 6 neural network toolbox is used for this study. The study results indicate that the neural networks are able to make accurate predictions even with the limited number of parameters. Results also show that increasing the topology of the network and number of the inputs, increases the accuracy of the network. Best results for the S02 forecasting are obtained with the network with two hidden layers, hyperbolic tangent function as transfer function and three input variables (R2 was found as 0,94 and daily average error was found as 3,6 j..lg/m3).The most accurate results for the dust forecasting are also obtained with the network with two hidden layer, hyperbolic tangent function as transfer function and three input variables (R2 was found as 0,92 and daily average error was found as 3,64 j..lg/m3).S02 and dust predictions using their last seven days values as an input are also studied, and R2 is calculated as 0,94 and daily average error is calculated as 4,03 Jlg/m3 for S02 prediction and R2 is calculated as 0,93 and daily average error is calculated as 4,32 Jlg/m3 for dust prediction and these results show that the neural network can make accurate predictions.
Assesment of the efficiency of UV light emitting diodes (UV-LEDS) for fruit juice pasteurization
(Izmir Institute of Technology, 2019-06) Akgün, Merve; Ünlütürk, Sevcan
The objectives of this thesis are to evaluate the application of ultraviolet light emitting diodes (UV-LEDs) with various wavelengths for pasteurization of cloudy (CAJ) and clear apple juices (AJ), to assess the disinfection efficiency of combined UV-LED irradiation and mild heat (UV-LED+MH) treatments, to investigate the effect of individual and combined processes on the activity of enzyme, physicochemical and microbiological quality of AJ, to determine the shelf life of UV-LED irradiated juice during storage, to reveal the reactivation potential of target microorganism (E. coli K12) in juice medium with different optical properties, and to elucidate the mechanism of microbial inactivation by UV-LEDs. 280/365 nm UV-LED irradiation assisted by mild heat at 55ºC and 15 min exposure time enhanced the inactivation of E. coli K12 and polyphenoloxidase and satisfied the 5-log reduction pasteurization criterion in apple juice. UV-LED+MH treatment extended the shelf life of CAJ from 3 to 30 days and increased its total phenolic content. However, the color properties were slightly affected by ultraviolet treatment. Subsequent photoreactivation of E. coli K12 after inactivation by UV-LEDs was observed in both CAJ and AJ. Contrarily, dark repair was repressed at 4ºC and 22ºC, furthermore, a decrease in the survival ratio was recorded in both medium. It was revealed that the damage of DNA repair enzymes and the proteins that form the outer cellular membrane of bacteria was highly induced by UV-C light at 280 nm. Additionally, the bactericidal effect of 365 nm (UV-A) wavelength was attributed to enhanced production of reactive oxygen species (ROS) resulting in oxidative damage to cellular lipids, proteins and DNA. The combination of these two wavelengths provided more efficient disinfection than that of UV-C light used alone. UV-LED irradiation assisted by mild heat has a potential to be used as an alternative technique to traditional thermal pasteurization process for juice products. This study leads to useful information for the future design of UV-LED treatment systems.
An assessment of spatial relationship between lung cancer incidence rate and quality of urban life: Izmir case
(Izmir Institute of Technology, 2013) Özkan, Sevim Pelin; Saygın, Mustafa Ömür
The study assesses spatial clusters of lung cancer incidences within Izmir province on the basis of districts and also neighborhood using an objective sets of quality of life indicators. Lung cancer data, approximately 18.000 cases, were acquired from the Izmir Cancer Registry Center (ICRC) between the years of 1992-2007. Cases have been confirmed in terms of accuracy by World Health Organization (WHO). As objective indicator data, point source air pollution data acquired from the Izmir Metropolitan Municipality database between the years of 1993-2007. Besides, socio-economic statistics data were obtained from Turkish Statistical Institute (TSI) regional indicators (2000,2007) and Izmir Metropolitan Municipality city health profile (2007). The datasets were used to determine whether there is a significant spatial relationship between cancer case density and environmental contamination. This thesis uses spatial statistical models and Geographical Information System (GIS) techniques to analyze population-based cancer incidence rate. Additionally, Age Standardized Incidence (ASR) of the lung cancer was calculated. Spatial autocorrelation technique was performed to investigate local distribution of lung cancer. Results of the study suggest that spatial clusters of lung cancer were detected in geographic locations with low level environmental quality and high level socio-economic profile. Then, the results are discussed in terms of life quality and environmental quality of Izmir. The results of this study are useful for interdisciplinary researchers, epidemiological studies, policymakers and governmental agencies in terms of health and environmental assessment, regulation and control of spatial strategies.
Assessment of wood laminated material for housing production
(Izmir Institute of Technology, 2019-07) Balkan, Selçuk; İnceköse, Ülkü
Today, laminated wood material is used in different types of structures. In many countries such as our country, as well as countries where this usage is intense, laminated wood material is not preferred in housing production yet. Although it seems that reinforced concrete structures have replaced wooden structures today, environmentally sensitive approaches expressed with concepts such as sustainability, ecological balance and repeatability have enabled the reuse of wood material. In this study, the properties of laminated wood technology, which is predicted to be an alternative technology to conventional construction technologies, are evaluated. With this assessment, laminated wood technology could be an alternative structure production technology in our country. At the beginning of the study, wood materials, wood damaging factors, composite wood materials, the use of wood in residential production and the use of laminated wood in residential production were examined under four main headings. The properties of wood materials and laminated wood materials were examined in detail and the methods, advantages and disadvantages of these materials were determined. This study is detailed on the structure of JZ House which was designed and built by architect Serhat AKBAY in Antalya with laminated wood technology. The laminated wooden parts produced for the building were examined based on scientific data on the design process, static resistance of the building, fire resistance, sustainability, environmental and human health contributions. With the evaluation, it is aimed to increase the preference of wooden structures constructed with developing wood technology.
B and Se transport modeling in saturated/unsaturated zones
(Izmir Institute of Technology, 2002-09) Yüreklitürk, O. Emin; Tayfur, Gökmen
There has been renewed interest in the application of models to the transport of non-point source pollutants. However, very little work has been done to evaluate the performance of a functional transient-state model for the transport of a reactive solute over an extensive study period. This research consists of mathematical modeling to simulate water flow, boron and selenium transport through soil in tile-drained croplands.For Boron part a mathematical model was developed to simulate non-conservative boron transport. The dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction. Two different models have been employed for the sorption of boron. Similarly, for selenium part a finite element model is developed to simulate species of selenium transport in two dimensions in saturated/unsaturated zones. The model considers water, selenate, selenite and selenomethionine uptake by plants. It also considers oxidation/reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. Comparison of boron transport model results with observed data is satisfactory. The model employed with Langmuir isotherm was found to give slightly better simulation results when compared with the model employed with Freundlich. The sensitivity analysis results indicate that the irrigation scheduling and the irrigation water quality are very important parameters for boron accumulation in the soil. Also the adsorption isotherm parameters, which reflect us the soil properties, are found to be important for the boron movement in the soil. Comparison of selenium transport model with observed data is not quite satisfactory in accuracy when compared with the model for boron transport. This may be the result of the complexity of the mechanisms affecting the selenium transport in soil. There are too many parameters, and due to the errors depending on the parameters, the total error for the estimation of the total selenium increases.
B-galactosidase of kluyveromyces lactis: Immobilization, characterization and hydrolysis behavior of enzyme
(Izmir Institute of Technology, 2008) Çabuk, Burcu; Harsa, Hayriye Şebnem
B-galactosidase (lactase) enzyme is of great industrial interest, since it can be used to solve problems associated with whey disposal and lactose crystallization in sweetened and frozen dairy products such as ice cream. All over the world, many people suffer from lactose intolerance and lactase preparations are used as supplements for these persons. B-galactosidase is also used to produce prebiotics since this enzyme hydrolyses lactose into galactooligosaccharides. Immobilized B-galactosidase preparations are preferred in many processes because they can be recycled and maintain their activities for a long time without loosing their chemical stability.Novel cross-linked chitosan-hydroxyapatite composite support has beenprepared, lactase from Kluyveromyces lactis was immobilized onto these beads. Lactase immobilization mechanism and effect of factors such as initial glutaraldehyde concentration, temperature, pH, initial lactase concentration, solid-liquid ratio on immobilzation mechanism were studied.Optimum cross-linking was obtained at the glutaraldehyde concentration of 100 mg/L. The optimum values of temperature, pH and solid/liquid ratio on lactase/HAChitosan were found to be 200C, pH 7.5 and 0.3g/ml Vg/Vl, respectively. The pH and thermal stabilities of free and immobilized enzymes were also investigated and it was observed that the relative activity remained above 83.2% within pH 6-7.5 and maximum activity yield was obtained at 370C for free and all immobilized enzymes. The Michaelis constant Km and Vmax of immobilized and free enzyme on chitosanhydroxyapatite composite beads were found to be 9.5 mM and Vm 454.5 .mol ONP min.1 mg.1 protein and 1.011 mM and 1098.9 .mol ONP min.1 mg.1 protein, respectively.
Bioactive compound retention and shelf life extension of strawberry juice by selected nonthermal processing technologies
(Izmir Institute of Technology, 2017-04) Yıldız, Semanur; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo V.
Shelf life extension of fruit juices while maintaining quality and functional properties is of great interest. Nonthermal food processing technologies have been emerged as innovative preservation methods alternative to thermal pasteurization of fruit juices. The objectives of this Ph.D. thesis were to (i) ensure microbial safety of strawberry juice (SJ) by thermal and nonthermal technologies, i.e. high pressure processing (HPP), ultrasound (US), pulsed electric field (PEF) and UV-C irradiation; (ii) evaluate physicochemical and phytochemical properties of SJ after processing and during storage; (iii) extend microbial shelf life of SJ without unduly affecting quality. HPP (300 MPa, 1 min), US (120 m, 5.15 J/mL, 55 C, 3 min), PEF (35 kV/cm, 27 s, 155 Hz), and thermal pasteurization (71.7 C, 15 s) conditions were determined based on equivalent inactivation of E.coli (ATCC 11775) in SJ studied at Washington State University. UV-C irradiation (1.01 J/mL, 53.9 C, 6 cycles, 5.8 min) and thermal pasteurization (72 C, 101 s) conditions were determined considering inactivation of E. coli K-12 (ATCC 25253) in SJ studied at IZTECH. Consequently, microbial shelf life of SJ treated by HPP, thermosonication, UVC+mild heating, thermal pasteurization was extended up to 42 days while PEF prolonged up to 35 days at refrigerated storage. Multivariate data analysis revealed that HPP and PEF enhanced phytochemical characteristics of SJ compared to thermosonication and thermal pasteurization. Although UV-C irradiation did not alter physcicochemical properties, total phenolic content, and antioxidant activities of SJ, total anthocyanin content was significantly decreased by UV-C light compared to untreated juice.
Biofuels production using canola oil over heterogeneous catalysts
(Izmir Institute of Technology, 2017-12) Özdoğru, Bertan; Şeker, Erol
The goal of this study was to investigate the activity of Ni loaded on Al2O3-SiO2 supports prepared with different acids for the production of biofuel grade compounds while using canola oil as our feedstock. While keeping the reaction conditions constant, catalyst preparation parameters such as aluminum concentration, nickel concentration, calcination temperature, and acid types investigated with statistical methods by constructing Box Behnken design using three continuous parameters with two levels and one categorical parameter with three level. Responses considered in this study were aldehyde, ester, organic acid and other compound yields calculated from the GC-MS analysis. After ANOVA analysis, empirical models calculated from this analysis used to optimize the catalyst preparation parameters. Three catalysts, one for each acid type, selected to investigate the validity of our model. Analysis did on these catalysts have shown that both 0% Ni/25% Al2O3-75% SiO2 w/H2SO4 at 900oC and 20% Ni/75% Al2O3-25% SiO2 w/H3PO4 at 900oC catalysts gave good ester yields with good organic acid utilization. 20% Ni/75% Al2O3-25% SiO2 w/H3PO4 at 900oC catalyst was exceptional in ester selectivity aspect while 0% Ni/25% Al2O3-75% SiO2 w/H2SO4 at 900oC catalyst was in organic acid utilization aspect. Presence of aluminum phosphate crystal phase observed with XRD resulted in 20% Ni/75% Al2O3-25% SiO2 w/H3PO4 at 900oC catalyst having the highest selectivity towards ester production. Combination of weak and strong acid sites increased the organic acid selectivity while lowering the selectivity towards esters for 0% Ni/25% Al2O3-75% SiO2 w/H2SO4 at 900oC catalyst. From the low organic acid utilization observed with 10% Ni/25% Al2O3-75% SiO2 w/HNO3 at 500oC and, 10% Ni/50% Al2O3-50% SiO2 w/H2SO4 at 700oC catalysts which had high amounts of weak acid sites, it could be said that organic acids can only be reacted over strong acid sites.
Characterization and classification of wines from grape varieties grovn in Turkey
(Izmir Institute of Technology, 2014) Şen, İlknur; Tokatlı, Figen
The wines of Turkish grapes from four vintages (2006-2009) were classified according to variety, geographical origin and vintage based on their chemical composition (element, polyphenol, color, acid, sugar, alcohol, pH, total phenol and brix) by using multivariate statistical techniques. In the varietal classification of red wines, the partial least square-discriminant analysis (PLS-DA) demonstrated the discrimination of Boğazkere-Öküzgözü, Kalecik Karası, Syrah and Cabernet Sauvignon varieties from each other as the significant element, polyphenol, organic acid, sugar and alcohol parameters were combined in the model. Boğazkere and Öküzgözü wines of East Anatolia were characterized with their high coumaroylated anthocyanin derivatives, while Syrah wines of West Anatolia were rich in anthocyanins and flavonols. Kalecik Karası wines were the poorest in terms of total phenol content. In the classification of white wines, Emir wines of Kapadokya region were characterized with their high Li, Sr and resveratrol contents. Sultaniye wines were the lowest in polyphenol content and Muscat wines were the richest in hydroxycinnamic acids. The regional discrimination of red and white wines was achieved with the significant element and polyphenol compositions. The western region wines were characterized with their higher Pb content which may be due to the industrialization of West Anatolia. Moreover, red wines of Tekirdağ region were recognized with their low flavonol-glycoside contents. 2009 vintage red wines were characterized with their high anthocyanin and flavonol contents. In the same way, 2009 vintage white wines had higher flavonols, flavonol-glycosides, phenolic acids and flavan-3-ols.
Chemical and enzymatic interesterification of tallow with different oils
(Izmir Institute of Technology, 2019-04) Aktaş, Ayşe Burcu; Özen, Fatma Banu; Yemişçioğlu, Fahri
The purpose of this study is to manufacture structured lipids by enzymatic and chemical interesterification of tallow with corn, canola and safflower oils individually and to investigate the effects of several process parameters on various chemical and physical properties of structured lipids. Moreover, collection of Fourier-transform mid infrared (FT-MIR) and near infrared (FT-NIR) spectra during interesterification process is also aimed in order to monitor the processes and to construct chemometric models for the prediction of chemical and physical properties of the interesterified products. Both enzymatic and chemical interesterification provided modification of the properties of tallow. The blend ratio is the most significant factor among the parameters investigated for both types of interesterification. Longer reaction time for enzymatic interesterification caused undesirable changes in physical properties of fats. Interesterified lipids have generally low trans fatty acids and they tend to have lower consistencies and solid fat contents compared to their physical blends and the tallow; as a result, they also acquired better spreadable and plastic behaviors. The structured lipids produced with chemical interesterification of tallow with corn oil have better physical properties, higher oxidative stability and lower free fatty acid content compared to structured lipids produced with other vegetable oils. Chemical and physical properties of interesterified fats could be predicted accurately with chemometric analysis of FT-NIR spectra.
Chemical characterization of olive oils from Karaburun Peninsula
(Izmir Institute of Technology, 2014-07) Uncu, Oğuz; Özen, Fatma Banu
Chemical 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.
Classification of Turkish virgin olive oils based on their phenolic profiles
(Izmir Institute of Technology, 2008) Ocakoğlu, Derya; Tokatlı, Figen
Virgin olive oil is different from other plant oils with its high phenolic content. The resistance to oxidation and the protection against some diseases has been linked to these components of olive oil. The sensorial characteristic of extra virgin olive oil is also related to its phenolic compounds.In this work, it is aimed to determine the phenolic profiles of Turkish olive oils, which have high economic value for Turkey. Phenolic profiles of monovarietal extra virgin olive oil samples extracted from six dominant and economically important Turkish olive cultivars (memecik, erkence, domat, nizip-yaglik, gemlik, ayvalik) and commercial extra virgin olive oil samples from two different areas (south and north) of the Aegean coast were determined for 2005 and 2006 harvest years. Total phenol contents, oxidative stabilities and chromatic ordinates as colour parameters were also measured. The effect of cultivar, geographical area and harvest year on phenolic profiles of olive oils was investigated. Multivariate data were subjected to principal component and partial least square-discriminant analyses.Typical phenolic substances of extra virgin olive oils from different variety and regions are; p-coumaric acid, cinnamic acid & apigenin for memecik, erkence oils and also for oils of south Aegean; vanillin & syringic acid for ayvalik, gemlik and also for oils of north Aegean. Domat oils were characterized by their relatively high content of oleuropein aglycon. Nizip oils were separated by their 4-hydroxyphenyl acetic acid content, which was determined in very low amounts or none in other olive oils. It was observed that harvest year strongly affected the phenolic profiles of olive oils. In addition, phenolic composition was found to be useful in discriminating the olive oils from different variety and geographical area.
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, Figen
Extra 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 TarisÌ§ 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.
Comparison of dipping and spraying methods in layer-by-layer deposition of chitosan and sodium caseinate
(Izmir Institute of Technology, 2016-08) Üney, Sinem; Bayramoğlu, Beste
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.
The confirmation of the commercial kits used in the detection of antibiotics in milk with HPLC (high pressure liquid chromatography)
(Izmir Institute of Technology, 2008) Alkan, Pınar; Tarı, Canan
In this study, Charm II Assay was confirmed by HPLC for B-lactam, sulphonamide and tetracycline residues in milk. These antibiotics were chosen because they are most frequently used veterinary drugs and their detection have importance for milk quality and consumer's health. The results for confirmation of Charm II Assay showed that the test was very sensitive to all groups that were investigated and showed %100 true results for blank samples and spiked samples that were fortified with mixed standards at MRL (maximum residue limit) for each group. Average recoveries of HPLC used for confirmation were between 47% to 97% for beta-lactams, 61.5% to 84.8% for tetracyclines and 50.4% to 54.6% for sulphonamides. The results of analysis with the naturally contaminated milk samples showed that Charm II Assay may give false positive results. But this might be because of the high sensitivity of the test that sometimes HPLC may not reach that detection limit of Charm II assay or the milk samples may contain other compounds of investigated antibiotics that HPLC method can not detect.In samples that were collected for B-lactam determination, only 2 out of 81 samples were detected above MRL where the amounts were 6.5 ppb penicilin-G and 23.8 ppb ampicillin. The MRL for these B-lactam antibiotics are specified as 4 ppb by European Union regulations. The samples investigated for tetracycline residues which were found as positive and confirmed by HPLC were below MRL or negative. In samples investigated for sulphonamides only one sample out of 44 was above MRL where the amount was 119 ppb sulfamethazine.Analysis with 5 commercial milk samples showed none antibiotic residues. Only 4 samples out of 5 for sulphonamides were screened positive but after confirmation no residues were detected in these samples.
Control of microbial and enzymatic changes in intermediate moisture sun-dried figs by mild heating and hydrogen peroxide disinfection
(Izmir Institute of Technology, 2003) Demirbüker Kavak, Dilek; Yemenicioğlu, Ahmet
During cold storage, the enzyme pectin methylesterase (PME) caused softening and lossof desired gummy texture in rehydrated intermediate moisture (IM) sun-dried figs. Heat inactivation studies indicated that the purified PME can be inactivated rapidly at 80 o and 90 oC. However, at or below 70 oC the enzyme showed activation by heating and inactivated very slowly. The in-situ activation of PME occurred much more extensively when sun-dried figs were rehydrated between 70o and 90 oC to produce IM figs with approximately 30 % moisture and this prevented the effective inactivation of enzyme even by rehydrations conducted at 80 o and 90 oC. The partial reduction of PME enzyme activity (almost 30 %) by rehydration of figs at 80 oC for 16 min may be used to delay undesirable textural changes in cold stored IM figs for 3 months. However, for longer storage periods hot reyhdration alone is not sufficient to prevent softening. No considerable yeast and mold growth was detected in IM figs cold stored 3-3.5 months.However, in some samples rehydrated in water at 80 oC, the total mesophilic aerobic counts and total yeast and mold counts showed a considerable increase when storage time exceeded 3-3.5 months. The rehydration of IM figs in 2.5 % H2O2 for 16 min at 80 oC reduced the total mesophilic aerobic microbial count of figs almost 90 %. Due to bleaching caused by H2O2, the brown fig color turned to a desirable and stable yellowlight brown as well. However, during cold storage the O2 gas released due to the decomposition of H2O2 by in situ fig catalase, accumulated within figs and caused some physical defects. Also, the residual level of H2O2 in the homogenates of disinfected figs was too much (300 ppm) and it seemed unlikely to eliminate this amount of H2O2 by physical or chemical means during processing. Pureeing IM figs eliminated residual H2O2 very rapidly. The application of rehydration first in 2.5 % H2O2 solution at 80 oC for 4 or 8 min and then in hot water at the same temperature for 12 or 8 min, respectively, also reduced the amount of residual H2O2 in IM figs considerably.Besides, these two-stage rehydration procedures eliminated the physical defects occurred in IM figs due to O2 gas release and gave firmer IM figs. To reduce the initial microbial load of IM figs, 4 and 8 min disinfections conducted in H2O2 solutions were less effective than 16 min disinfection in H2O2 solution. However, both 4 and 8 min disinfections effectively suppressed microbial load for at least 3.5 months and they may be used in the production of SO2 free light colored fig products.

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