Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of High Stability Antioxidant Emulsions Based on Citrus and Fig Pectins(Izmir Institute of Technology, 2022) Yemenicioğlu, Ahmet; Yemenicioğlu, Ahmet; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this thesis, stability and antioxidant activity of olive oil-in-water emulsions prepared with citrus pectin (CPEC) and pectins extracted from two fig cultivars (Sarılop: FPECn and Siyah Orak: FPECc) were evaluated in the presence of green tea (GTE) and grape seed extracts (GSE), and a basic monomeric flavonoid, (+) catechin (CAT). The emulsion stabilities of FPECn and FPECc between 0.125 and 1% (w/v) were comparable to those of CPEC. Control olive oil-in-water emulsions with 0.5% CPEC, FPECn or FPECc prepared without the addition of polyphenols lost 29 to 36% of their initial emulsion stability only within 1 day. The addition of GSE at 0.25 or 0.5% caused a considerable increase in the stability of emulsions prepared with CPEC at 0.5% (less than 10% loss in emulsion stability within 14 days) while GTE caused only a limited increase in the stability of CPEC emulsions. The CAT is the only polyphenol that caused significant increases in the stability of all pectin emulsions. In contrast, both GTE and GSE showed almost no effect in stability of FPECn and FPECc emulsions. The polyphenol added emulsions were characterized for their droplet size, zeta potential and viscosities. The CAT and GSE added emulsions showed significantly higher total phenolic content and antioxidant activity than GTE added emulsions during 14 days of storage. This thesis clearly showed that GSE and CAT stabilized CPEC emulsions, and CAT stabilized FPECn or FPECc emulsions have a great potential to develop novel antioxidant olive oil based functional foods.Master Thesis Conversion of Hazelnut Shell Into Value-Added Chemicals by Using Sub-Critical Water as a Reaction Medium(Izmir Institute of Technology, 2016) Gözaydın, Gökalp; Yüksel Özşen, Aslı; Yüksel Özşen, Aslı; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe objective of this study is to clarify the effect of reaction temperature, reaction time, acid concentration and acid type on the hydrothermal conversion of waste hazelnut shell into value-added chemicals under hot compressed water with high temperature/high pressure autoclave. The other aim is to gaining of added value and new utilization field to waste hazelnut shell. This is the first study about the degradation of waste hazelnut shell in order to produce levulinic acid under subcritical water in literature. Reactions were performed at 150-280 °C of reaction temperature, 15-120 min of reaction time with different acid (H2SO4 and H3PO4) concentrations that was varied from 0 to 125 mM. The liquid product distribution was evaluated with High Performance Liquid Chromatography (HPLC) and Gas Chromatography-Mass Spectrometry (GC-MS) and gas products were identified by Gas Chromatography with a Thermal Conductivity Detector (GC-TCD). While levulinic acid, acetic acid and furfural were identified as a major liquid compounds, the main gaseous products were carbon dioxide and carbon monoxide. Increasing reaction temperature and reaction time improved the conversion of hazelnut shell up to 65.40% at 280 °C and 120 min in the presence of 50 mM H2SO4 and 13.05% of levulinic acid yield was obtained under the similar reaction conditions. Addition of dilute H2SO4 and H3PO4 in the reaction medium enhanced different product formation. H2SO4 treatment promoted the production of levulinic acid whereas addition of H3PO4 increased the formation of furfural. Furthermore, total phenolic content, antioxidant capacity and possible reaction pathways of hydrothermal conversion of waste hazelnut shell was evaluated.