Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Strained Yogurt Ice Cream With Aronia and Hydrolyzed Collagen(01. Izmir Institute of Technology, 2024) Güler, Sevda; Korel, FigenYogurt ice cream, made using yogurt cultures Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, is integrated with freezing technology, and it is a healthy food that creates cooling effect on consumers. In this study, it was aimed to obtain strained yogurt ice cream that would allow consumption of hydrolyzed collagen and aronia together. Different concentrations of collagen were added to samples with and without aronia. Different amounts of stevia were also added to selected sample due to its antioxidant activity. The quality of the ice creams in the study were evaluated by analyses as follows; dry matter, protein, fat, ash, carbohydrates, pH, color, viscosity, overrun, melting rate, antioxidant activity, coliform and lactic acid bacteria counts, and sensory analyses. While aronia decreased pH, collagen increased pH; adding stevia did not cause any significant change on pH. A correct proportion was observed between the viscosity and fat content of formulations. Samples were examined for antioxidant activity by DPPH and total phenolic content analyses. According to DPPH analysis results, sample B containing 20g of aronia had highest antioxidant activity. According to total phenolic content analysis, sample F containing 20g of aronia and 2.5g of hydrolyzed collagen had the highest total phenolic content. After the antioxidant activity was evaluated, stevia was added as a sweetener to sample E, which contained 1g of hydrolyzed collagen. According to sensory analysis results, sample E1 containing 20g of aronia, 1g of collagen and 0.006g of stevia was the most liked yogurt ice cream in terms of taste.Master Thesis Development of a Functional Snack(01. Izmir Institute of Technology, 2023) Maşa, Zeynep Tuğba; Korel, Figen; Sezgin, EfeNowadays, with the increasing animal food prices, many people in our country are malnourished because they cannot get the necessary protein in their bodies. Additionally, with the Corona virus, which entered our lives in 2019, many people had to struggle with various mental disorders. Although we have left behind the pandemic period, negative emotional states such as depression and unhappiness are still observed in many people today. In this direction, vegetables rich in protein were investigated and used in developing functional snacks. In this study, vegetable chips dough was prepared with 40% pea flour content 15, 17.5, 20, 22.5, and 25% radish, 20, 22.5, 25, 27.5, and 30% zucchini, and 10, 12.5, 15, 17.5, and 20% pumpkin seeds. Each vegetable chip mix was cooked at 50°C, 55°C, and 60°C with the aid of a tray dryer. The proximate analyses (moisture, ash, fat and protein), chemical analyses (antioxidant activity and total phenolic content), physical analyses (color and texture) and sensory analysis were carried out. Mixture design was created with the help of MINITAB 16.0 (Minitab Inc., State College, PA, USA) program, the results of the analyses were evaluated statistically. Based on the design, it was decided to bake thirteen different mixtures at three different temperatures and to perform all the analyzes mentioned above. As a result of the evaluation of all analyses results, the optimized sample was determined as the vegetable chips sample with 40% pea flour, 22.5% zucchini, 25% radish, and 12.5% pumpkin seeds baked at 60°C. The vegetable chips, with this mixture, were baked at 50°C, 55°C and 60°C in the a tray dryer, and in addition to all analyses, sensory analysis and antioxidant activity analysis for all samples baked at 50°C, 55°C and 60°C were conducted. The sample baked at 60°C was the most liked sample.Master Thesis Investigation of Microwave Processing for Pasteurization of Vegan Milk Products(01. Izmir Institute of Technology, 2021) Erol, Büşra; Korel, Figen; Erdoğdu, FerruhIn this study microwave processing was applied for the pasteurization of three different vegan milk products (almond, soy, and oat milk). For microwave process, 360 Watt power applied for 38 seconds. Also, results were compared with conventional thermal treatment which was carried out in a water bath at 70 ℃ during come-up times and 30 seconds holding time. For three vegan milk products, dielectric properties were investigated at different temperature values. After the treatments, important quality properties such as color, pH, particle size distribution and zeta potential values were evaluated. After all treatments, more than 5- log reduction of Salmonella Enteritidis was observed in three vegan milk products. Dielectric properties generally were significantly changed with temperature and frequency (p <0.05). Color differences of vegan milk samples were not perceptible or perceptible through close observation. The pH values generally were not affected by the heat treatments for soy and oat milk (p >0.05). Only there is a significant increase in the almond milk pH value with the heat treatments (p <0.05). Only soy milk's zeta potential values were significantly affected by the different processes (p <0.05). However, microwave pasteurized samples gave the closest value to untreated samples. Also holding process affected the stability of the oat milk. Particle size diameters were changed after the different processes. According to the results, the holding process is not required for the conventional pasteurization at 70 ℃. Microwave heating could be a promising new pasteurization method for vegan milk.Master Thesis Development of Bio-Based Coatings as Flexible Food Packaging Applications(Izmir Institute of Technology, 2018) Adalı, Merve Betül; Korel, FigenThe sustainable packaging solutions require the development of materials based on renewable resources and efficient production methods, which are important nowadays. In this study, a multilayer coated flexible polyethylene terephthalate (PET) sheets were produced by Layer-by-Layer (LbL) assembly using chitosan and pectin bio-based materials incorporated with galls extract (GE) as an active agent. These fabricated films were firstly characterized and results of increasing the depositing of chitosan and pectin from 0 to 60 layers indicated that the deposition of biopolymers successfully improve the performance of flexible films. The optimization of the deposition different number of layer on PET (20 – 40 and 60 layers) was carried out by the study of the surface characterization and the shelf-life tests in order to find out surface modification. The coated LbL films were applied on fresh-cut ‘Abate Fetel’ pears and color, microbial, sensory assays were carried out during 7 days of storage at 4 ºC. At the end of storage, in terms of all tests, the LbL treated samples were presented better preserved compared to the control samples (treated base film). In addition, the release of active agents from multilayer films was evaluated using LbL films in contact with food and gradual reduction was observed. This research demonstrates the feasibility of LbL coating, which acts as a carrier of active substances to enhance the quality of fresh-cut products as an active packaging system.Master Thesis Development of a Novel Active Packaging System Based on Layer-Sy Layer Deposition of Natural Antioxidants and Antimicrobials To Extend Food Products' Shelf Life(Izmir Institute of Technology, 2017) Akgün, Begüm; Korel, FigenIn recent years, Layer-by-Layer (LbL) assembly of thin films has been extensively investigated for many purposes, particularly for its functionality and simplicity of fabrication. Through LbL assembly; antioxidant agents have beenincorporated into active packaging systems in different forms, mainly including sachets, physical adsorption on packaging material surface, multilayer films which contact with food packaging surface. In previous studies, active packaging systen associated with LbL depositions were investigated, but no detailed investigation has been found about the application of controlled releasing-active packaging system on fresh-cut fruits. In this study, 20 bilayers of chitosan and alginate; respectively; were coated on amorphous polyethylene terephthalate (A-PET) sheets by dipping method. The LbL treated PET films were used for active packaging of fresh-cut peaches. Total soluble solids content and titrable acidity demonstrated that LbL active coating did not interfere with the natural postharvest behaviour. A lower weight loss was observed for LbL coated peach saples, suggesting that the presence of layer structure on PET strips could act as a barrier against fruit water loos. After 7 days of storage, the LbL treated samples have shown the best preservation of carotenoids, the lower PPO activity and higher phenolic index. Microbiological analysis has shown that all the microbiological analysis has that all the microorganism types which were invetigated were affected by the actice packaging system.Sensory results were really encouraging, as well. As a conclusion, LbL coating has been proved for being a useful technique to produce controlled-release active packaging systems on fresh-cut fruits.Master Thesis Effects of Preharvest and Postharvest Treatments on Quality Characteristics of Grapes(Izmir Institute of Technology, 2016) Konuk, Dilara; Korel, FigenGray mold, caused by Botrytis cinerea, is the most important disease which causes major quality and quantity losses in preharvest period and postharvest storage of grapes. Grapes are commonly treated with sulfurdioxide (SO2) to control decay caused by Botrytis cinerea both in vineyard and during storage. However, there is need for natural alternatives to replace SO2 because of many considerations related with sulfite residues, emergence of B.cinerea resistant strains, hazards for human and environment, negative effects on quality characteristics and sustainability, and certification for organic grapes. In this study, the effects of alginate solution with or without (w/wo) vanillin as preharvest spray and postharvest edible coating on quality, safety and biochemical properties of grapes from Semillon Blanc, Alphonse Lavalleé and Razaki cultivars were investigated. Soluble solid content, pH, titratable acidity, total phenolic content, antioxidant activity, yeast-mold counts, lactic acid content, color, and firmness were determined at the day of preharvest treatment, at harvest and during 35 days of storage at 4±2°C. In addition, sensory evaluation of grapes coated w/wo vanillin were also performed using hedonic scale test. Alginate treatments w/wo vanillin were effective in preventing weight, soluble solids, acidity, and firmness losses. Incorporation of vanillin into alginate coating provided significant reduction in yeast-mold growth. Moreover, phenolic content and antioxidant activity of grapes treated with alginate coating incorporating vanillin were higher than others during postharvest storage. In sensory evaluation, appearance was ranked as the highest for alginate coating wo vanillin. As a conclusion, alginate solution enriched with vanillin could be a natural alternative of synthetic fungicides to prevent deteriorations and enhance quality of grapes.Master Thesis Effects of Olive Variety, Harvest Time, and Malaxation Temperature on Volatile Compounds and Sensorial Characteristics of Olive Oils(Izmir Institute of Technology, 2015) Yıldız, Gamze; Korel, FigenIn this study, it was aimed to determine the differences between sensory properties of olive oils based on types of olives, malaxation temperature and harvest time. Olive oil samples were extracted from two different Turkish olive cultivars (Ayvalık and Memecik), provided by Tariş Olive and Olive Oil Agricultural Sales Cooperatives Union. Olives which were harvested at three different stages of ripening (early (first harvest time), mid (second harvest time) and late (third harvest time)) were extracted at three different malaxation temperatures (27°C, 37°C, 47°C). Samples were classified into eighteen groups by two olive varieties, by three harvest time and malaxation temperatures. Totally, 36 samples (18 treatments × 2 replicates) were obtained from two parallel extraction processes. The effects of cultivar, malaxation temperature and harvest time on volatile composition, sensory properties and color of olive oils were investigated. SIMCA 13.0.3 (Umetrics AB, Umeå, Sweden) and multilevel factorial experimental design were used for data analysis and result interpretation. As a conclusion, it was found that cultivar and harvest time of olives had a significant effect on sensorial characteristics of olive oils. However, no obvious effect of malaxation temperature was observed.Master Thesis Mechanical and Gas Permeability Properties of Nanocomposite Films Made From Low Density Polyethylene and Carbon Nanotubes(Izmir Institute of Technology, 2014) Anggoro, Bayu Meta; Korel, FigenIt is important to develop new food packaging materials with enhanced properties. In this work, nanocompositewas prepared by melt blending linear low density polyethylene (LLDPE) and multiwalled carbon nanotubes (MWCNT) by using twin-screw extruder, then hot-pressing was applied to produce nanocomposite films. The effect of the addition of three different dimensions of MWCNT on the mechanical and gas permeabilities properties was investigated, along with overall migration. According to the film characterization results by scanning electron microscopy, the dispersion of MWCNT in general was considerably average. The presence of interaction networks between LLDPE–MWCNT was observed, so did the presence of carbon nanotubes agglomerations. Relatively better dispersion was achieved by the nanocomposite films containing 0.25 wt. % MWCNT at any dimension. It was observed that the dispersion of carbon nanotubes corresponded with the improvement in mechanical and gas barrier properties. The consistent improvement was shown in Young‘s modulus with the increment up to 26.9 % as the content of MWCNT increased. Moreover, the addition of MWCNT could enhance the gas barrier properties by lowering the gas permeabilities up to 26.5 % and 32 % for oxygen and carbondioxide, respectively. The results from mechanical properties and gas permeabilities revealed that the content of MWCNT was more crucial to affect the improvement rather that its dimension. In terms of overall migration, the results were found below the limit required by European Union Commission (10 mg/dm2). Considering these outstanding results, the developed material could be applied in food packaging, particularly in active packaging system.Master Thesis Antimicrobial Properties of Silk Fibroin-Carrageenan Films Incorporating Grape Seed Extract(Izmir Institute of Technology, 2009) Arserim Uçar, Dilhun Keriman; Korel, FigenIn this study antimicrobial edible films were developed by incorporation of grape seed extract into silk fibroin-carrageenan films. Developed films were subjected to instrumental analysis such as scanning electron microscopy, atomic force microscopy, X-ray diffractometer, and Fourier transform infrared spectrometer for the characterization of the film. The antimicrobial activity of silk fibroin-carrageenan films on different bacteria including Listeria innocua, Staphylococcus aureus, Staphylococcus carnasus, Bacillus amyloliquefaciens, Escherichia coli, Pseudomonas fluorescens, Escherichia coli O157:H7, and Salmonella Typhimurium, on raw chicken breast meat and beef sausages were tested. Application of silk fibroin-carrageenan films incorporating grape seed extract and/or Na2EDTA on chicken breast meat and beef sausages demonstrated the efficacy of these films to enhance the microbial quality of the products. Increasing the concentration of grape seed extract in the films increased the antimicrobial activity of the films in food applications. It is found that silk fibroin-carrageenan films incorporating grape seed extract could be used to control the growth of S. aureus on beef sausages during 28 days of storage at 4 C. The use of these films on beef sausages had significant effect on moisture content of the sausages as well as the textural properties of the sausages. This study indicated the potential of using silk fibroin-carrageenan films incorporating grape seed extract to be used as an antimicrobial edible food packaging.Master Thesis 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, FigenExtra 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 Tariş 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.