sami gökhan özkal | Pamukkale University (original) (raw)

Papers by sami gökhan özkal

Food Control, Jan 1, 2011

Changes in chemical (pH, moisture, salt, ash, fat, protein, free fatty acids (FFA), thiobarbituri... more Changes in chemical (pH, moisture, salt, ash, fat, protein, free fatty acids (FFA), thiobarbituric acid reactive substances (TBARS) and residual nitrite contents), colour (Hunter L*, a* and b*, hue angle, chroma (saturation index), browning index (BI) and total colour difference (DE)) and microbiological (total mesophilic aerobic bacterial (TMAB), lactic acid bacteria (LAB), total Enterobacteriaceae (TE) and Staphylococcus and Micrococcus (SM)) quality characteristics of traditional fermented sausage "sucuk" during fermentation were investigated and kinetic modeling of these parameters were performed, in this study. The fermentation of the sucuk lasted 9 days. Analysis of the quality parameters was run on the beginning of the fermentation and on the 1st, 2nd, 3rd, 4th, 5th and 9th days of the fermentation process. Changes in the chemical and colour parameters were represented by zero, first and second order kinetic models. Microbial increments were represented by linear (first order kinetic) models and reductions were represented by both linear and Weibull distribution models.

Turkish Journal of Engineering & …, Jan 1, 2001

Energy Conversion and …, Jan 1, 2011

Tobacco seed oil has been evaluated as a feedstock for biodiesel production. In this study, all p... more Tobacco seed oil has been evaluated as a feedstock for biodiesel production. In this study, all properties of the biodiesel that was produced from tobacco seed oil were examined and some solutions were derived to bring all properties of the biodiesel within European Biodiesel Standard EN14214 to verify biodiesel quality. Among the properties, only oxidation stability and iodine number of the biodiesel, which mainly depend on fatty acid composition of the oil, were not within the limits of the standard. Six different antioxidants that are tert-butylhydroquinone, butylated hydroxytoluene, propyl gallate, pyrogallol, a-tocopherol and butylated hydroxyanisole were used to improve the oxidation stability. Among them, pyrogallol was found to be the most effective antioxidant. The iodine number was improved with blending the biodiesel produced from tobacco seed oil with a biodiesel that contains more saturated fatty acids. However, the blending caused increasing the cold filter plugging point. Therefore, four different cold flow improvers, which are ethylene-vinyl acetate copolymer, octadecene-1-maleic anhydride copolymer and two commercial cold flow improvers, were used to decrease cold filter plugging point of the biodiesel and the blends. Among the improvers, the best improver is said to be octadecene-1-maleic anhydride copolymer. In addition, effects of temperature on the density and the viscosity of the biodiesel were investigated.

The purpose of this research was to determine the solubility of apricot (Prunus armeniaca L.) oil... more The purpose of this research was to determine the solubility of apricot (Prunus armeniaca L.) oil in supercritical carbon dioxide (SC-CO 2 ), effects of parameters (particle size, solvent flow rate, pressure, temperature and co-solvent (ethanol) concentration) on extraction yield and to investigate the possibility of fractionation. iv Solubility, increased with pressure and increased with temperature above the crossover pressure, which was found between 200 and 300 bar, and decreased with temperature below the crossover pressure. Appropriate models were fitted to data.

Journal of the American Oil Chemists' Society, Jan 1, 2009

Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of part... more Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of particle size, pressure, temperature and the flow rate of supercritical carbon dioxide (SC-CO 2 ) were investigated. Response surface methodology was used to determine the effects of pressure (30-50 MPa), temperature (50-70°C) and SC-CO 2 flow rate (2-4 g/min) on flaxseed oil yield in SC-CO 2 . The oil yield was represented by a second order response surface equation (R 2 = 0.993) using the Box-Behnken design of experiments. The oil yield increased significantly with increasing pressure (p \ 0.01), temperature (p \ 0.05) and SC-CO 2 flow rate (p \ 0.01). The maximum oil yield from the response surface equation was predicted as 0.267 g/g flaxseed for 15 min extraction of 5 g flaxseed particles (particle diameter\0.850 mm) at 50 MPa pressure and 70°C temperature, with 4 g/min solvent flow rate. Total extraction time at these conditions was predicted as 22 min.

European Food Research …, Jan 1, 2005

Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g... more Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/ min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 C) on hazelnut oil yield in supercritical carbon dioxide (SC-CO 2 ). Oil yield was represented by a second order response surface equation (R 2 =0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO 2 flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diame-ter<0.85 mm) were extracted with 5 g/min SC-CO 2 flow rate at 450 bar, and 60 C for 10 min. Total extraction time at these conditions was predicted to be 35 min.

International journal of food …, Jan 1, 2006

The Journal of supercritical fluids, Jan 1, 2005

The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.

LWT-Food Science and Technology, Jan 1, 2005

Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g... more Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/ min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 C) on hazelnut oil yield in supercritical carbon dioxide (SC-CO 2 ). Oil yield was represented by a second order response surface equation (R 2 =0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO 2 flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diame-ter<0.85 mm) were extracted with 5 g/min SC-CO 2 flow rate at 450 bar, and 60 C for 10 min. Total extraction time at these conditions was predicted to be 35 min.

Journal of food engineering, Jan 1, 2005

Solubility of hazelnut oil in supercritical carbon dioxide (SC-CO 2 ) was determined at 15-60 MPa... more Solubility of hazelnut oil in supercritical carbon dioxide (SC-CO 2 ) was determined at 15-60 MPa, and 40-60°C. The crossover pressure of hazelnut oil was between 15 and 30 MPa. The solubility increased with pressure, but increased with temperature above the crossover pressure. Hazelnut particles (1-2 mm) were extracted at 30-60 MPa, and 40-60°C with SC-CO 2 flow rate of 2 ml/min. Extraction occurred in two periods. The released oil on the surface of particles was extracted in the fast extraction period, and 39% of the initial oil was recovered at each condition. However, the duration of the fast extraction period decreased with increased pressure and temperature. The unreleased oil in the intact cells was extracted in the slow extraction period. The maximum recovery was 59% at 60 MPa and 60°C, for 180 min of extraction. The fluid phase and solid phase mass transfer coefficients increased with increased pressure and temperature.

Food Control, Jan 1, 2011

Changes in chemical (pH, moisture, salt, ash, fat, protein, free fatty acids (FFA), thiobarbituri... more Changes in chemical (pH, moisture, salt, ash, fat, protein, free fatty acids (FFA), thiobarbituric acid reactive substances (TBARS) and residual nitrite contents), colour (Hunter L*, a* and b*, hue angle, chroma (saturation index), browning index (BI) and total colour difference (DE)) and microbiological (total mesophilic aerobic bacterial (TMAB), lactic acid bacteria (LAB), total Enterobacteriaceae (TE) and Staphylococcus and Micrococcus (SM)) quality characteristics of traditional fermented sausage "sucuk" during fermentation were investigated and kinetic modeling of these parameters were performed, in this study. The fermentation of the sucuk lasted 9 days. Analysis of the quality parameters was run on the beginning of the fermentation and on the 1st, 2nd, 3rd, 4th, 5th and 9th days of the fermentation process. Changes in the chemical and colour parameters were represented by zero, first and second order kinetic models. Microbial increments were represented by linear (first order kinetic) models and reductions were represented by both linear and Weibull distribution models.

Turkish Journal of Engineering & …, Jan 1, 2001

Energy Conversion and …, Jan 1, 2011

Tobacco seed oil has been evaluated as a feedstock for biodiesel production. In this study, all p... more Tobacco seed oil has been evaluated as a feedstock for biodiesel production. In this study, all properties of the biodiesel that was produced from tobacco seed oil were examined and some solutions were derived to bring all properties of the biodiesel within European Biodiesel Standard EN14214 to verify biodiesel quality. Among the properties, only oxidation stability and iodine number of the biodiesel, which mainly depend on fatty acid composition of the oil, were not within the limits of the standard. Six different antioxidants that are tert-butylhydroquinone, butylated hydroxytoluene, propyl gallate, pyrogallol, a-tocopherol and butylated hydroxyanisole were used to improve the oxidation stability. Among them, pyrogallol was found to be the most effective antioxidant. The iodine number was improved with blending the biodiesel produced from tobacco seed oil with a biodiesel that contains more saturated fatty acids. However, the blending caused increasing the cold filter plugging point. Therefore, four different cold flow improvers, which are ethylene-vinyl acetate copolymer, octadecene-1-maleic anhydride copolymer and two commercial cold flow improvers, were used to decrease cold filter plugging point of the biodiesel and the blends. Among the improvers, the best improver is said to be octadecene-1-maleic anhydride copolymer. In addition, effects of temperature on the density and the viscosity of the biodiesel were investigated.

The purpose of this research was to determine the solubility of apricot (Prunus armeniaca L.) oil... more The purpose of this research was to determine the solubility of apricot (Prunus armeniaca L.) oil in supercritical carbon dioxide (SC-CO 2 ), effects of parameters (particle size, solvent flow rate, pressure, temperature and co-solvent (ethanol) concentration) on extraction yield and to investigate the possibility of fractionation. iv Solubility, increased with pressure and increased with temperature above the crossover pressure, which was found between 200 and 300 bar, and decreased with temperature below the crossover pressure. Appropriate models were fitted to data.

Journal of the American Oil Chemists' Society, Jan 1, 2009

Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of part... more Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of particle size, pressure, temperature and the flow rate of supercritical carbon dioxide (SC-CO 2 ) were investigated. Response surface methodology was used to determine the effects of pressure (30-50 MPa), temperature (50-70°C) and SC-CO 2 flow rate (2-4 g/min) on flaxseed oil yield in SC-CO 2 . The oil yield was represented by a second order response surface equation (R 2 = 0.993) using the Box-Behnken design of experiments. The oil yield increased significantly with increasing pressure (p \ 0.01), temperature (p \ 0.05) and SC-CO 2 flow rate (p \ 0.01). The maximum oil yield from the response surface equation was predicted as 0.267 g/g flaxseed for 15 min extraction of 5 g flaxseed particles (particle diameter\0.850 mm) at 50 MPa pressure and 70°C temperature, with 4 g/min solvent flow rate. Total extraction time at these conditions was predicted as 22 min.

European Food Research …, Jan 1, 2005

Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g... more Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/ min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 C) on hazelnut oil yield in supercritical carbon dioxide (SC-CO 2 ). Oil yield was represented by a second order response surface equation (R 2 =0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO 2 flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diame-ter<0.85 mm) were extracted with 5 g/min SC-CO 2 flow rate at 450 bar, and 60 C for 10 min. Total extraction time at these conditions was predicted to be 35 min.

International journal of food …, Jan 1, 2006

The Journal of supercritical fluids, Jan 1, 2005

The user has requested enhancement of the downloaded file. All in-text references underlined in b... more The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.

LWT-Food Science and Technology, Jan 1, 2005

Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g... more Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/ min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 C) on hazelnut oil yield in supercritical carbon dioxide (SC-CO 2 ). Oil yield was represented by a second order response surface equation (R 2 =0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO 2 flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diame-ter<0.85 mm) were extracted with 5 g/min SC-CO 2 flow rate at 450 bar, and 60 C for 10 min. Total extraction time at these conditions was predicted to be 35 min.

Journal of food engineering, Jan 1, 2005

Solubility of hazelnut oil in supercritical carbon dioxide (SC-CO 2 ) was determined at 15-60 MPa... more Solubility of hazelnut oil in supercritical carbon dioxide (SC-CO 2 ) was determined at 15-60 MPa, and 40-60°C. The crossover pressure of hazelnut oil was between 15 and 30 MPa. The solubility increased with pressure, but increased with temperature above the crossover pressure. Hazelnut particles (1-2 mm) were extracted at 30-60 MPa, and 40-60°C with SC-CO 2 flow rate of 2 ml/min. Extraction occurred in two periods. The released oil on the surface of particles was extracted in the fast extraction period, and 39% of the initial oil was recovered at each condition. However, the duration of the fast extraction period decreased with increased pressure and temperature. The unreleased oil in the intact cells was extracted in the slow extraction period. The maximum recovery was 59% at 60 MPa and 60°C, for 180 min of extraction. The fluid phase and solid phase mass transfer coefficients increased with increased pressure and temperature.