Master Degree / Yüksek Lisans Tezleri
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Master Thesis Lazer ve İğneli Mikro-perforasyon Ön İşlemlerinin Kavacık Üzümünün Kurutma Süresine ve Bazı Kalite Özelliklerine Etkisinin Araştırılması(2025) Ünlütürk, Sevcan; Ünlütürk, Sevcan; 01. Izmir Institute of Technology; 03. Faculty of Engineering; 03.08. Department of Food EngineeringTez kapsamında, coğrafi işaretli ve iri taneli bir çeşit olan Kavacık üzümlerine (Vitis vinifera L. cv. Alphonse Lavallée), lazer ve iğne mikro-perforasyon ön işlemleri kullanılarak kurutma yoluyla değer katılması amaçlanmıştır. Çalışmada, kurutma performansı ve biyoaktif bileşikler ile kalite özellikleri üzerindeki etkiler incelenmiştir. Kabin kurutucu (statik yöntem) ve hızlı kurutma için bir Airfryer (konvektif yöntem) kullanılmıştır. Üzümlere alkali bandırma, iğne ve lazer mikro-perforasyon ön işlemlerine uygulanmış ve 60, 70 ve 80°C'de kurutulmuştur. Kurutma davranışı, rehidrasyon oranı, fiziksel özellikler, toplam biyoaktif içerik, hidroksimetilfurfural (HMF) seviyeleri ve enerji tüketimi analiz edilmiştir. İğne veya lazer mikro-perforasyon ile uygulanan üzümler ile alkali çözeltiye bandırılan üzümler arasında fiziksel özelliklerde veya toplam fenolik, antioksidan ve antosiyanin içeriklerinde anlamlı bir fark gözlenmemiştir (P > 0,05). Kurutma davranışı ve enerji sonuçları, iğne mikro-perforasyon işleminin alkali bandırma kadar etkili olduğunu, lazer işleminin ise optimizasyon gerektirdiğini göstermiştir. Ayrıca, tüm ön işlemler dondurarak kurutmadan önce uygulanmış ve karşılaştırılmıştır. İğne mikro-perforasyon ve alkali bandırma, antioksidan kapasitesini önemli ölçüde etkilememiş, ancak lazer mikro-perforasyon işlemi toplam fenolik ve antosiyanin içeriğini daha iyi korumuştur. Sonuç olarak, iğne ve lazer mikro-perforasyon ön işlemleri, Kavacık üzümü gibi iri taneli meyvelerin kurutulmasında kimyasal alkali çözelti bandırmaya göre etkili fiziksel alternatifler olup, benzer kalite ve kimyasal içermeyen işleme potansiyeli sunmaktadır. Anahtar kelimeler: Kavacık üzümü, Kurutma, Ön işlem, Mikro-perforasyonMaster Thesis Investigation of Applicability of Uv-Light Emitting Diodes (uv-Leds) as an Alternative Technology in Pasteurization of Cold-Pressed and Newly Formulated Mixed Beverage(Izmir Institute of Technology, 2022) Baykuş, Gökçen; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aims of this thesis were to evaluate the cold pressing technique for juice extraction and to evaluate whether the cold pressed mixed beverage can be pasteurized with ultraviolet light emitting diodes (UV-LEDs) using E. coli K12 as the target microorganism. Initially, the physical, chemical and optical properties of cold pressed juice (CPJ) were compared with juice extracted by centrifugal juicer (CDJ). The CPJ was then exposed to UV-LEDs simultaneously and sequentially and the microbial inactivation was evaluated. Besides, barrier technologies have been tried to increase the UV-LED inactivation effect. It has been found that the juice yield performance of the cold pressing technique is better than the centrifuge method. The total phenolic content of the CDJ and CPJ was 922 ± 0.01 mg GAE/L, and 867.25 ± 0.01 mg GAE/L, respectively. However, DPPH radical scavenging activity of both beverages were not significantly different. The use of UV-LEDs in simultaneous or sequential mode could not achieve a 5-log reduction in pertinent microorganism required as part of HACCP mandated by US Federal regulations for juice issued by the Food and Drug Administration (FDA). However, filtration and addition of ginger juice revealed that the inactivation efficiency of UV-LEDs increased in highly turbid juice reaching to 3.65 ± 0.218 log10 CFU/ml. In conclusion, this study showed that UV-LEDs used simultaneously at different wavelengths may have the potential to be used in turbid cold press juice pasteurization when combined with different barrier technologies.Master Thesis Investigation of the Usability of Radiochromic Films for Determination of Dose Uniformity of Food Surface in Uv-C Treatment(Izmir Institute of Technology, 2022) Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe microbial inactivation efficiency of UV light is dependent on product shape and surface morphology on non-planar food surfaces. Since every point of the product is not exposed to the same level of UV light, the efficiency decreases. In addition, during UV light illumination, blind spots may occur, and sufficient inactivation cannot be achieved. So, it is essential to determine UV fluence (dose) applied to surfaces. Actinometry, biodosimetry and mathematical techniques are used to evaluate UV fluence on solid surfaces and in liquid foods. In this study, use of radiochromic films (RCFs) integrated with a computer vision system (CVS) based on image analysis is proposed as an alternative method to evaluate UV fluence on food surfaces. For this purpose, the color change of RCFs on non-planar surfaces exposed to different UV intensity and exposure time was correlated with UV fluence. The results were compared with actinometric and radiometric measurement techniques. Experimental results have been tested and verified on real food surfaces such as apples. It was revealed that there is a linear correlation between the color change of RCF and UV fluence. The maximum UV fluence that could be determined using RCF at 254 nm was approximately 60 mJ/cm2. It was found that films were stable up to 15 days at room and refrigerated conditions. The shape of the apples resulted in different UV fluence distribution profiles on the surface. As a result, it has been demonstrated that RCFs can be successfully used to determine UV fluence on sample surfaces.Master Thesis Rheological, Textural, Physico-Chemical and Sensory Properties of Low Sugar Apple Marmalade(Izmir Institute of Technology, 2019) Şirin, Pınar; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyHomemade low-sugar apple marmalade formulations were developed by partial replacement of sucrose with sweeteners such as stevioside and sucralose (25%, 50%) without using commercial pectin and chemical preservative additives. The objectives of this study were to formulate and optimize the composition of ingredients for the best quality low sugar marmalade production, to determine the rheological, textural and physicochemical properties and overall acceptability of formulated marmalades. The concentration of sweeteners was found to have a significant effect on the physicochemical and rheological properties of the formulations. The hardness of the sweetener added marmalades decreased due to the reduction of total soluble solids (TSS). The marmalade samples had pseudo-plastic behavior exhibiting yield stress. Yield stress of the marmalade increased with increasing TSS content upon increasing sweeteners concentration. Herschel–Bulkley model was found to be the best model describing the time-independent rheological behavior of formulated marmalade samples. The consistency index decreased with raising the sweeteners substitution, whereas the flow behavior index showed increasing trend with the increase of the sweeteners content. From the sensory point of view, low sugar marmalades made by substituting 50% of the sugar content with stevioside have been shown to be as acceptable as marmalade containing only 500g of sucrose.Master Thesis Investigation of the Pyhsical and Chemical Properties of Milk Containing Antibiotics(Izmir Institute of Technology, 2008) Yıldız, Özge; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis work aimed to find a basic and rapid screening method for antibiotic residues in UHT whole cow.s milk. For this purpose an investigation was conducted to screen some physical (e.g. acidity, pH, density, freezing point and electrical conductivity), thermo-physical (e.g. melting temperature, heat of fusion, evaporation temperature and heat of evaporation) and chemical properties (e.g. fat%, protein%, lactose%, minerals%, SNF%) of antibiotic free milk and milk fortified by Penicillin G, Ampicillin, Tetracycline. We can able determine whether residue of antibiotics making any difference on these selected properties. Thermo-physical properties were measured by differential scanning calorimeter (DSC), (TA Instruments, USA) and chemical properties were determined by using Lactostar (Funke Gerber Inc., Berlin, Germany).Antibiotic residues were detected by Copan Milk Test, Penzyme Test and ROSA Test and by high performance liquid chromatography (HPLC) method for confirmation of screening tests. Due to some drawbacks of screening tests, liquid chromatography was required for confirmation of antibiotic residues in milk. HPLC method showed that average recoveries of spiked Penicillin G at 2, 4, 8 ppb, spiked Ampicillin at 2, 4, 8 ppb and spiked Tetracycline at 100, 250, 500 ppb were ranged from 44.67% to 66.00%, from 62.50% to 87.52% and from 92.86% to 94.35%, respectively.We found that the acidity, pH and density of milk were independent of Penicillin G, Ampicillin and Tetracycline concentrations. Electrical conductivity (EC) were evaluated by applying ANOVA with Fisher.s test and Probabilistic neural network (PNN) method. ANOVA was also performed for DSC and Lactostar measurement results. This evaluation suggested that EC measurement can be a great promising technique for detection of antibiotic residues in milk, DSC is a good characterization tool for understanding of thermal events and the presence of antibiotic residues in milk influencing freezing point and minerals (EMC)%.Master Thesis Investigation of the Effects of Dissolved Oxygen Concentration, Aeration and Agitation on the Morphology and Rheology in Submerged Fungal Fermentation(Izmir Institute of Technology, 2007) Öncü, Şelale; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe effects of pH, agitation speed, dissolved oxygen tension (DOT) and aeration, significant in common fungal fermentations, on the production of polygalacturonase (PG) enzyme and their relation to morphology and broth rheology were investigated in a batch bioreactor using Aspergillus sojae which has no available literature report on the pectinase production. All four factors were effective on the response parameters under study. An uncontrolled pH increased biomass and PG activity by 27% and 38%, respectively compared to controlled pH (pH 6). pH did not significantly affect the broth rheology but created an impact on the pellet morphology. Similarly, the maximum biomass obtained at 500 rpm and at 30h was 3.27 and 3.67 times more than at 200 and 350 rpm, respectively. The maximum enzyme productivity of 0.149 U ml-1 h-1 was obtained at 200 rpm. Non . Newtonian and pseudoplastic broth rheology was observed at 500 rpm agitation speed. Furthermore, a DOT range of 30-50% was essential for maximum biomass formation, whereas only 10% DOT was required for maximum PG synthesis. Non . Newtonian shear thickening behavior (n>1.0) was depicted at DOT levels of 10% and 30%, whereas, non-Newtonian shear thinning behavior (n<1.0) was dominant at 50% DOT. When 2.5 l/min aeration experiment was investigated detaily; it was determined that at about 21st hour, polygalacturonase production approaches its maximum (1.49 U) and pellets are smaller, high in number. At 48th hour; polygalacturonase production declines to zero, biomass reaches its maximum and pellets are big (average pellet size is 1.94±0.58 mm) and fluffy with compact centers. At the end of fermentation (96.hour), fermentation medium is close to Newtonian. The overall fermentation duration (50-70h) was considerably shorter as opposed to common fungal fermentations revealing the economic feasibility of this particular process. As a result this study not only introduced a new strain with a potential of producing a highly commercially significant enzyme but also provided certain parameters significant in the design and mathematical modelling of fungal bioprocesses.Master Thesis Disinfection of Liqued Egg Products by Using Uv Light(Izmir Institute of Technology, 2007) Atılgan, Mehmet Reşat; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe application of UV treatment to continuous flow of liquid egg products is the initial study among the others. The objective of this study was to investigate the efficiency of UV-C radiation as a non-thermal pasteurization process for liquid egg products (LEPs). The outcomes of this study were evaluated from the rheological, biodosimetric and inactivation efficiency points of view. The results pertaining to rheological characterization, physical and optical measurements of the fresh and pasteurized LEPs indicated that liquid whole egg (LWE) and liquid egg white (LEW) showed Newtonian behavior within the range studied. Liquid egg yolk (LEY) exhibited pseudoplastic and time independent behavior in temperature ranges from 4 C to 25 C. But its rheological behavior was affected at pasteurization temperature and showed thixotropy and time dependent. The biodosimetric study based on the UV treatment of LEPs by using collimated beam apparatus pointed out that the best reduction was achieved in liquid egg white (LEW) when the fluid depth and UV dose were 0.153 cm and 98 mJ/cm2, respectively. Maximum inactivation was 0.675-log CFU/ml in liquid egg yolk (LEY) and 0.316-log CFU/ml in liquid whole egg (LWE). The kinetics of UV inactivation of E.coli in LEPs was found nonlinear. Our results emphasize that UV-C radiation can be used as a pre-treatment process or combined with mild heat treatment to reduce the adverse effects of thermal pasteurization of LEPs. The efficacies of short wave ultraviolet light (UV-C) as a non-thermal process for LEW were investigated in the continuous flow UV reactor based on the result derived from the biodosimetric study. Maximum 0.2 log reduction was achieved after 5 cycle of operation. The efficiency of the UV light treatment in continuous flow UV reactor was found to be lower compared to bench-top studies. This is attributed to the problems caused by inefficient design of UV chamber. Results of these work showed that the UV reactor was designed poorly to supply enough UV irradiation exposure for all the fluid elements in the system. Redesigning of the system was suggested.Master Thesis Uv Disınfection of Some of the Fruit Juices(Izmir Institute of Technology, 2009) Hakgüder, Bengi; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAlthough UV-C irradiation is used in the pasteurization of certain liquids, the application to white grape juice is not sited in the literature. Besides there are a few studies about the inactivation of naturally grown microorganisms by using UV-C treatment. The objective of this study was to determine the effect of UV-C treatment on the inactivation of Escherichia coli K12 inoculated into white grape juice and naturally grown microorganisms in the fresh squeezed orange juice. Also, the effect of UV light on the colors of the products was determined. The data were evaluated considering the properties of the juices. Results of microbiological analysis of white grape juice showed that, maximum log reduction was more than 5-log CFU/mL at a UV dose of 75.04 mJ/cm2 when the inoculation rate was 5.73 (l20.114) log CFU/mL. Although a 5-log reduction requirement of FDA was satisfied with white grape juice, maximum log reduction for the naturally grown microorganisms in orange juice was only 1.76-log CFU/mL even if the sample was subjected to UV dose of 144.36 mJ/cm2. Color analysis demonstrated that orange juice color was not affected from the treatment. For white grape juice, increased UV dose caused a decrease in a* value indicating slightly more green region.Also, increased intensity and sample depth had a pronounced effect on b* value of the juice showing yellow region. As a conclusion, UV-C light can be used as an alternative technique in processing of white grape juice. Combination of UV-C with other techniques is suggested to increase the microbiocidal efficiency in orange juices.Master Thesis Disinfection of White Grape Juice by Using Continuous Flow Uv Reactor(Izmir Institute of Technology, 2011) Kaya, Zehra; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAlthough continuous flow UV irradiation process is applied to several kind of fruit juices as a non-thermal method, it hasnot treated to white grape juice before. The main objective was to study the effect of commercial UV disinfection system on the spoilage microorganisms in white grape juice. Physical, chemical and optical properties were measured after and before irradiation. Biodosimetric studies were performed by using Bench Top UV apparatus and continuous flow commercial UV reactor. Bench top UV study showed that 228.96 mJ/cm2 UV dose provided complete inactivation of S. cerevisiae in the pasteurized juice at 0.91 mW/cm2 UV intensity.. 3.00±0.16 log cfu/ml yeasts and 4.32±0.03 log cfu/ml lactic acid bacteria reduction were detected in naturally fermented juice after 282.24 mJ/cm2 UV dose. D(10) of yeasts (43.86 mJ/cm2) were higher than lactic acid bacteria (33.78 mJ/cm2) because of showing higher resistance to UV light. In the continuous flow UV reactor, the highest reduction of S. cerevisiae was achieved as 3.39±0.044 log cfu/ml at 56.06 mJ/cm2 UV dose and low flow rate (820 ml/min) in pasteurized juice. However, highest reduction was observed in yeast and lactic acid bacteria count as 1.70±0.028 log cfu/ml and 2.49±0.0031 log cfu/ml respectively at 19.96 mJ/cm2 UV dose in medium flow rate (1516 ml/min) of fresh squeezed juice. Absorbance, color, and titratable acidity were changed by irradiation. As a result of 13 days shelf life study, no significant increase was seen in spoilage microorganisms after irradiation.Master Thesis Determination of Antibiotics in Raw and Uht Milk Samples by the Image Forming Method of Biocrystallization(Izmir Institute of Technology, 2011) Pelvan, Merve; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis study aims to investigate a new technique for the antibiotic residue analysis that can able to detect a wide range of antibiotic residues directly in raw and drinking milk by producing reliable and definitive results. "Biocrystallization method" was selected as a new technique to distinguish the raw and UHT milk samples containing antibiotic residues from the antibiotic free ones. This method is based on the crystallographic phenomenon that occurs after adding ionic substances to an aqueous solution of dihydrate CuCl2 and drying in a constant temperature and relative humidity. In this study, the raw and UHT milk samples was screened for antibiotic residues using New SNAP* Beta-Lactam (IDEXX Lab. USA) test kits. Then, the chemical properties of milk samples (e.g. fat%, protein%, lactose%, minerals%, SNF%) were determined. At the same time, biocrystallization method were optimized with antibiotic free raw milk samples. Evaluation of biocrystallograms was performed via a panel. The best biocrystallogram images were obtained for 6 ml of milk samples prepared from 0.5 % milk and 5% CuCl2.2H2O solution by mixing at a ratio of 3 (milk) to 1 (CuCl2.2H2O) dried at 30 °C ,60% relative humidity for 22 h. After optimization, the raw and UHT milk samples were spiked with Penicillin G (2, 4, 8 ppb) and Ampicillin (2, 4, 8 ppb) to generate biocrystallogram images at the optimized conditions. All the images were evaluated with a visual inspection. Biocrystallization method was successfully used to distinguish raw and UHT milk from the samples spiked with Penicillin G and Ampicillin. This method gave better results when discriminating naturally contaminated raw milk from antibiotic free raw milk.