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Öğe Adsorption behavior of Cr(VI) on activated hazelnut shell ash and activated bentonite(Elsevier, 2006) Bayrak, Y; Yesiloglu, Y; Gecgel, UThe possible use of activated hazelnut shell ash and activated bentonite as the adsorbents of Cr(VI) from synthetic solutions and the effect of operating parameters were investigated. The activated hazelnut shell ash was prepared thermally in two sizes 0.5 and 1.0 mm. The maximum removal of Cr(VI) occurred at pH 3 by activated hazelnut shell ash and at pH 5 by activated bentonite. The amounts of Cr(VI) adsorbed increased with increase in dose of both adsorbents and their contact time. The equilibrium data was analysed using the Langmuir and Freundlich isotherms. The characteristics parameters for each isotherm were determined. The Freundlich adsorption model was applied to describe the equilibrium isotherms and the isotherm constants were determined. The Freundlich model agrees very well with experimental data. (c) 2005 Elsevier Inc. All rights reserved.Öğe Antibacterial effect of Turkish black cumin (Nigella sativa L.) oils(Inst Grasa Sus Derivados, 2005) Arici, M; Sagdic, O; Gecgel, UA series of five different oils from Turkish black cumin (Nigella sativa) used in foods mainly for their flavour, preservation and natural therapies were screened for their antibacterial effects at 0.5%, 1.0% and 2.0% concentrations using the agar diffusion method against twenty four pathogenic, spoilage and lactic acid bacteria (LAB). All tested oils showed antibacterial activity against all the bacteria used in the assay. The oils at 2.0% concentration were more effective than of the other concentrations. The most sensitive bacterium against all of the oil concentrations was Aeromonas hydrophila, while the most resistant was Yersinia enterocclitica. Generally, lactic acid bacteria had more resistance than pathogenic and spoilage bacteria against black cumin oils. Consequently, black cumin oil may be used as an antimicrobial agent in food products to prevent spoilage.Öğe Changes in oxidative stability of selected bakery products during shelf life(Japanese Soc Food Sci & Technology, 2004) Daglioglu, O; Tasan, M; Gecgel, U; Daglioglu, FIn this research, selected bakery products that contain high amount of fat (> 10%) were stored under ambient conditions until the end of shelf life. Changes in oxidative stability and fatty acid composition of the samples including biscuits, crackers, wafer and fruit cake were determined with three months of interval. Free fatty acidity, peroxide value, and Rancimat induction times changed significantly (p < 0.05) in all samples. However, acidity and peroxide values remained under the maximum limits allowed by standarts. Total fat contents ranged from 13.3% (petit beurre) to 27.1% (wafer), and the major fatty acids in the samples were palmitic, stearic, oleic, trans oleic, and linoleic acids. Changes in unsaturated fatty acids which majorly affects the lipid oxidation were insignificant (p > 0.05), and according to the obtained results all samples maintained their oxidative stability throughout shelf life.Öğe Determination of FA composition and total trans FA of Turkish margarines by capillary GLC(Amer Oil Chemists Soc A O C S Press, 2002) Arici, M; Tasan, M; Gecgel, U; Ozsoy, SIn this research, FA composition and total trans FA contents of 16 different brands of margarine (8 hard-type and 8 soft-type) sold in Turkey were determined by capillary GLC method. According to the results, the contents of saturated FA, monounsaturated FA, and PUFA were within the ranges of 23.9-32.3, 44.0-61.9, and 14.2-24.1%, respectively, in hard-type margarines, and 27.0-39.9, 21.0-40.9, and 32.0-53.79%, respectively, in soft-type margarines. Hard-type margarines contained total trans FA concentrations of 20.1-34.3%, whereas softtype margarines contained less than 8.9% total trans FA. C-18:1 trans acid content was within the range of 18.5-29.8% in hard type margarines, and it was significantly higher than the range in soft margarines (0.7-8.1%). C-18:1 trans acid was the in all. or trans FA in all margarines, and C-18:3 trans acid concentrations were less than 0.2%.
