Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Subject: search.filters.subject.Vegetable oils

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  • Master Thesis
    Effect of Deep-Frying on the Quality Parameters of Vegetable Oils
    (Izmir Institute of Technology, 2015) Avcı, Başak; Özen, Fatma Banu; Tokatlı, E.Figen; Özen, Fatma Banu; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    It 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
    Methyl Ester Production From Vegetable Oils on Heterogeneous Basic Catalysts
    (Izmir Institute of Technology, 2008) Umdu, Emin Selahattin; Şeker, Erol; Şeker, Erol; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, the activities of heterogeneous mixed oxide catalysts; magnesium and calcium oxide on alumina and silica supports were investigated for transesterification of vegetable oils; canola and sunflower, to methyl esters. The primary objective of this study is to understand whether basicity of the solid catalysts and/or its crystallite size affect the biodiesel yield during the reaction. The mixed oxide catalysts were prepared by a single step sol-gel method. Magnesium oxide (MgO) and calcium oxide (CaO) were chosen because of their basic property.This study shows that the crystallite size does not have any direct effect on the transesterification activity. Yet, the interaction of the crystallites with the support material may change the number of the active sites and/or the creation of new .basic. sites. In fact, the basicity was found as the critical factor for the choice of the suitable mixed oxide for the transesterification reaction. The addition of CaO to alumina creates synergetic effect. But this is not observed with the catalysts: CaO/SiO2 and also the MgO/Al2O3 and MgO/SiO2.CaO/Al2O3 differs from the others in such a way that it contains the basic sites with the mild basic strength. Not only the crystallite size but also the type of the oxide is important to obtain the heterogeneous catalysts as active as the homogeneous catalyst. CaO/Al2O3 has the same activity as that of NaOH for the transesterification of canola and sunflower oils at 50 oC. It was also found that the activity of CaO/Al2O3 was truly heterogeneous.
  • Master Thesis
    Use of Domestic Minerals for Vegetable Oil Bleaching
    (Izmir Institute of Technology, 2004) Erten, Yasemin; Ertürk, Handan; Ertürk, Handan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this thesis, acid activation and characterization studies were conducted for different clay samples and bleaching capacity of the selected acid activated clay samples for sunflower oil were determined. The samples selected for this study were naturally occuring clays from Ankara and Eskiehir regions. The acid activated zeolite was also used for the purpose to compare its bleaching performance with commercial bleaching clay, Tonsil and the acid activated clays.The clay minerals were activated with hydrochloric acid (HCl) at three acid concentrations (1 N, 3 N, 5 N), activation times (1h, 2h, 3h) and different dry clay/acid ratios. The clay samples from the Ankara and Eskiehir regions were defined as montmorillonite according to X- ray diffraction (XRD). XRD results proved that acid activation caused structural changes in the treated montmorillonites, montmorillonite peaks gradually disappearing and yielding to an amorphous montmorillonite structure.The TGA results showed a significant weight loss between 30 C - 200 C ( 15%) for the Ankara clay and between 20 - 200 (12%) for the Eskiehir clay. This was most probably due to the removal of free and hydrogen-bonded water molecules. Maximum surface area was obtained for the acid activated Ankara clay treated with 1 N HCl for 3 hours. It was determined to be 849.1 m2/g. Also, maximum surface area was 269.7 m2/g for the acid activated Eskiehir clay treated with 5 N HCl for 1hour. Then the surface area of the acid activated clays decreased sharply with the acid activation. The chemical compositions of the solutions and clays after acid activation were determined using ICP and EDX analysis, respectively. According to the results, the dissolution amount of CaO, Na2O, MgO, K2O, Fe2O3 and Al2O3 increased along with increasing acid concentration and treatment time. The SiO2 content and the Si02/Al2O3 ratio increased as a result of dissolving of aluminium ions. This ratio increased from 6.0 to 7.5 for the acid activated Eskiehir clay and from 2.7 to 3.9 for acid activated Ankara clay.Acid activated clays were tested for the assessment of their bleaching efficiency for sunflower oil in the laboratory. Bleaching tests were carried out with earths prepared at different acid activation conditions such as acid concentration and activation times. The absorbance value was measured at 455 nm and found to be 0.429 for the neutralized sunflower oil. Peroxide value and free-fatty acid content of the neutralized oil were found to be 16.8 meq/kg and 0.07 %, respectively. The oil bleached with the acid activated Ankara clay had a peroxide value of 46.2 meq/kg first, which decreased to 22.4 meq/kg and the free-fatty acid content was observed to be around 0.08 %. For acid activated Eskiehir clay, peroxide value of the bleached oil initially increased up to 31.2 meq/kg, then decreased under the peroxide value of neutralized oil (16.8 meq/kg) and free-fatty acid content of bleached oil approximately was around 0.09 %.The bleaching parameters which were used for testing were 1 % earth concentration and 30 minutes contact time at 100°C bleaching temperature. At these selected parameters, acid activated Eskiehir clay (5 N 1h HCl treatment), Ankara clay (1 N 3h HCl treatment) and zeolite (2 N 6h HNO3 treatment) were compared with the commercial bleaching clay, Tonsil. The smallest value of absorbance and bleaching efficiency were found to be 0.084 and 80 %, respectively with the Eskiehir clay and these values were determined to be 0.083 and 81 % with the Tonsil under the same conditions. The absorbance value and bleaching efficiency of the bleached oil with acid activated Ankara clay were determined to be 0.114 and 73 %, respectively using the selected bleaching parameters. Bleaching performance of Ankara clay was found to be lower when compared with the result of Eskiehir clay.At the selected bleaching point, results of lovibond red and yellow color of bleached oil indicated that the Eskiehir clay and Tonsil were close to each other in bleaching efficiency (Red color: 0.8 and 1.1; yellow color: 20 and 20 for Tonsil and Eskiehir clay, respectively). Zeolite did not reach the required bleaching performance.The bleaching efficiency was 25 % with raw zeolite and it hardly increased to 46 % with the acid activated zeolite. In addition, red and yellow color values were higher than the other clays (red color:2.6; yellow color: 30).As a result, Eskiehir clay gave a better bleaching performance compared to Ankara clay and Zeolite. Maximum bleaching efficiency was achieved after 30 minutes of contact time with 1 % earth concentration at 100 °C bleaching temperature following 5 N 1h HCl treatment for Eskiehir clay.