Murat özdemir | Okyanus Danışmanlık (original) (raw)
Papers by Murat özdemir
Drying Technology, 2001
Adsorption isotherms of raw and roasted (at 100 C, 120 C, 140 C and 160 C) hazelnuts of Tombul va... more Adsorption isotherms of raw and roasted (at 100 C, 120 C, 140 C and 160 C) hazelnuts of Tombul variety were determined at 25 C, and over relative humidities ranging from 11 to 90% using the gravimetric static method. Eleven sorption models (GAB, BET, Modified BET, Halsey, Iglesias-Chirife, Oswin, Chung-Pfost, Smith, Kuhn, Harkins-Jura and Caurie) were evaluated by using the linear regression method. GAB (Guggenheim-Anderson-de Boer) model satisfactorily described adsorption characteristics of the samples over the experimental range of study. Monolayer values at 25 C were estimated from the GAB model as 0.0155 kg water/kg dry 691 solid for raw and 0.0100-0.0163 kg water/kg dry solid for roasted hazelnuts. Caurie security moisture content for raw hazelnuts was also determined from Caurie model as 0.048 kg water/kg dry solid.
Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during r... more Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10−7 to 21.5×10−7m2/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.
Critical Reviews in Food Science and Nutrition
ABSTRACT: Turkey produces about 80% of the total hazelnut crop of the world. About 75% of the pro... more ABSTRACT: Turkey produces about 80% of the total hazelnut crop of the world. About 75% of the production
are exported. In Turkey hazelnuts are traditionally sun dried, and may be subject to mold growth and subsequent
mycotoxin formation due to prolonged drying time under humid and rainy weather conditions. Drying hazelnuts
in a reasonable time after harvest is necessary for mycotoxin-free, high-quality products. In general, nuts and
cereals contaminated by the toxins pose a potential hazard not only to the people of the producer countries, but
also to people of the importing countries, if they should be regarded as safe by inefficient sampling plans, therefore
preventing toxin formation actually benefits very large populations.
Deterioration and health hazards associated with toxin contaminated hazelnuts and other nuts and cereals have
similar causes and consequences; therefore, deterioration of the nuts and cereals in storage has been reviewed by
considering as many grains and nuts as possible, then special reference was made to hazelnuts. Proper preharvest
practices followed by proper drying and safe storage reduces the hazards associated with contamination by the
toxins. This article reviews the pre- and post-harvest practices, and the grain- and nut-drying systems required for
toxin-free products. Because drying is the major unit operation involving this process, the drying systems and the
mathematical models required for their design is also discussed.
Food Chemistry, 2001
Formation of internal browning in hazelnuts during roasting and eect of water activity on interna... more Formation of internal browning in hazelnuts during roasting and eect of water activity on internal browning were studied. Water activity signi®cantly aected color attributes of roasted hazelnuts. As the water activity increased internal browning also increased. Over the water activity range of study (0.29±0.83), water activity of 0.29 was found to be the least susceptible to internal browning. Roasted samples, having dark-coloured internals contained signi®cantly more total sugar and sucrose than roasted samples, having light coloured internals. Brown centres contained more total sugar and sucrose than light-coloured outer layers. Inner layers of raw hazelnuts contained about 50% more total sugar and sucrose than light-coloured outer layers. Polyphenoloxidase activity could not be detected in the sample roasted at 130 o C for 16 and 30 min. These results indicated that internal browning during roasting was due to localised concentration of reactants and, subsequently, the higher non-enzymatic browning reaction rate in the centre of hazelnuts. #
Food Chemistry, 1999
Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated ... more Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated in terms of total oil, fatty acid composition, a-tocopherol, unsaturated/saturated ratio, stability index and mineral in comparison with ®ve commercial Turkish hazelnut varieties (Tombul, Palaz, Mincane, FosË a and C Ë akõldak). Signi®cant dierences in total oil, fatty acid composition, stability index, a-tocopherol content and mineral composition were observed between varieties. The highest stability index values were observed in commercial Tombul (6.29), FosË a (5.93) and Palaz (5.42) varieties. No signi®cant advantage of new hybrid varieties over commercial varieties was observed in terms of stability of hazelnuts. #
Journal of Food Engineering, 1999
Thin layer drying characteristics of hazelnuts during roasting were described for a temperature r... more Thin layer drying characteristics of hazelnuts during roasting were described for a temperature range of 100±160°C, using ®ve semi-theoretical and two empirical thin layer models. The eective diusivity varied from 2X301 Â 10 À7 to 11X759 Â 10 À7 m 2 /s over the temperature range. Temperature dependence of the diusivity coecient was described by Arrhenius-type relationship. The activation energy for moisture diusion was found to be 1891.6 kJ/kg. Thin layer drying characteristics of hazelnut roasting were satisfactorily described by an empirical Thompson model with the linear temperature dependence. Ó
Journal of Agricultural Engineering Research, 1997
The quality of hazelnuts, sized and cracked by different systems was compared in a commercial pro... more The quality of hazelnuts, sized and cracked by different systems was compared in a commercial processing plant by determining the percentages of nuts that were damaged, broken, left-in the-shell, cracked, unbroken, recyclable, or undamaged. Hazelnuts larger than 16 mm diameter had different cracking behaviour, as compared with smaller ones. In experiments with a traditional Turkish cylindrical sizer and stone cracker
Journal of Food Engineering, 2000
Hazelnut roasting was analyzed using response surface methodology to ®nd out the eect of process ... more Hazelnut roasting was analyzed using response surface methodology to ®nd out the eect of process variables on color development during roasting and to establish prediction models. The roasting temperature was found to be the main factor aecting color development. Developed prediction models satisfactorily described color development as a function of roasting temperature and exposure time for L-value, a-value and b-value of whole-kernel, ground-state and cut-kernel measurements. Whole-kernel measurements were signi®cantly lighter in color compared to ground-state and cut-kernel measurements due to internal browning of the hazelnuts during roasting. The results also indicated that the L-value of ground-state measurements, which take into account internal browning during roasting, should be used to monitor roasting of hazelnuts. Ó
Food Chemistry, 2001
Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated ... more Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated in terms of total oil, fatty acid composition, a-tocopherol, unsaturated/saturated ratio, stability index and mineral in comparison with ®ve commercial Turkish hazelnut varieties (Tombul, Palaz, Mincane, FosË a and C Ë akõldak). Signi®cant dierences in total oil, fatty acid composition, stability index, a-tocopherol content and mineral composition were observed between varieties. The highest stability index values were observed in commercial Tombul (6.29), FosË a (5.93) and Palaz (5.42) varieties. No signi®cant advantage of new hybrid varieties over commercial varieties was observed in terms of stability of hazelnuts. #
Fett-lipid, 1998
The oil content, fatty acid and sterol compositions and other parameters of pistachio nut (Pistac... more The oil content, fatty acid and sterol compositions and other parameters of pistachio nut (Pistacia vera L.) samples corresponding to five different varieties, all cultivated in Turkey were determined. Mean values were 59.69 ± 1.80% for fat content, 0.9143 ± 0.006 for specific ...
Journal of Food Engineering, 2000
Kinetics of color changes during hazelnut roasting was described for a temperature range of 100±1... more Kinetics of color changes during hazelnut roasting was described for a temperature range of 100±160°C for 60 min. The rate of color changes was signi®cantly aected by temperature and time over the experimental conditions. Roasted hazelnut samples produced signi®cantly lower L-value and b-value in ground-state color measurements compared to whole-kernel measurements. The results showed that color changes during hazelnut roasting can be satisfactorily described by a third-degree polynomial with an Arrhenius-type temperature dependence of the model coecients. Activation energy for the L-value of color was found to be 62.3 kJ/mol over the temperature range of the study. A generalized model for color changes during roasting of hazelnuts as a function of temperature and time was established. Ó
Food Chemistry, 2001
Changes in total amino acid composition, thiamine and riboflavin contents, peroxide value and fre... more Changes in total amino acid composition, thiamine and riboflavin contents, peroxide value and free fatty acid contents were determined in roasted Giresun and Akçakoca hazelnuts. The results showed that roasting significantly affected peroxide value, free fatty acids, ...
Drying Technology, 2000
Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during r... more Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10−7 to 21.5×10−7m2/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.
Drying Technology, 2001
Adsorption isotherms of raw and roasted (at 100 C, 120 C, 140 C and 160 C) hazelnuts of Tombul va... more Adsorption isotherms of raw and roasted (at 100 C, 120 C, 140 C and 160 C) hazelnuts of Tombul variety were determined at 25 C, and over relative humidities ranging from 11 to 90% using the gravimetric static method. Eleven sorption models (GAB, BET, Modified BET, Halsey, Iglesias-Chirife, Oswin, Chung-Pfost, Smith, Kuhn, Harkins-Jura and Caurie) were evaluated by using the linear regression method. GAB (Guggenheim-Anderson-de Boer) model satisfactorily described adsorption characteristics of the samples over the experimental range of study. Monolayer values at 25 C were estimated from the GAB model as 0.0155 kg water/kg dry 691 solid for raw and 0.0100-0.0163 kg water/kg dry solid for roasted hazelnuts. Caurie security moisture content for raw hazelnuts was also determined from Caurie model as 0.048 kg water/kg dry solid.
Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during r... more Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10−7 to 21.5×10−7m2/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.
Critical Reviews in Food Science and Nutrition
ABSTRACT: Turkey produces about 80% of the total hazelnut crop of the world. About 75% of the pro... more ABSTRACT: Turkey produces about 80% of the total hazelnut crop of the world. About 75% of the production
are exported. In Turkey hazelnuts are traditionally sun dried, and may be subject to mold growth and subsequent
mycotoxin formation due to prolonged drying time under humid and rainy weather conditions. Drying hazelnuts
in a reasonable time after harvest is necessary for mycotoxin-free, high-quality products. In general, nuts and
cereals contaminated by the toxins pose a potential hazard not only to the people of the producer countries, but
also to people of the importing countries, if they should be regarded as safe by inefficient sampling plans, therefore
preventing toxin formation actually benefits very large populations.
Deterioration and health hazards associated with toxin contaminated hazelnuts and other nuts and cereals have
similar causes and consequences; therefore, deterioration of the nuts and cereals in storage has been reviewed by
considering as many grains and nuts as possible, then special reference was made to hazelnuts. Proper preharvest
practices followed by proper drying and safe storage reduces the hazards associated with contamination by the
toxins. This article reviews the pre- and post-harvest practices, and the grain- and nut-drying systems required for
toxin-free products. Because drying is the major unit operation involving this process, the drying systems and the
mathematical models required for their design is also discussed.
Food Chemistry, 2001
Formation of internal browning in hazelnuts during roasting and eect of water activity on interna... more Formation of internal browning in hazelnuts during roasting and eect of water activity on internal browning were studied. Water activity signi®cantly aected color attributes of roasted hazelnuts. As the water activity increased internal browning also increased. Over the water activity range of study (0.29±0.83), water activity of 0.29 was found to be the least susceptible to internal browning. Roasted samples, having dark-coloured internals contained signi®cantly more total sugar and sucrose than roasted samples, having light coloured internals. Brown centres contained more total sugar and sucrose than light-coloured outer layers. Inner layers of raw hazelnuts contained about 50% more total sugar and sucrose than light-coloured outer layers. Polyphenoloxidase activity could not be detected in the sample roasted at 130 o C for 16 and 30 min. These results indicated that internal browning during roasting was due to localised concentration of reactants and, subsequently, the higher non-enzymatic browning reaction rate in the centre of hazelnuts. #
Food Chemistry, 1999
Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated ... more Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated in terms of total oil, fatty acid composition, a-tocopherol, unsaturated/saturated ratio, stability index and mineral in comparison with ®ve commercial Turkish hazelnut varieties (Tombul, Palaz, Mincane, FosË a and C Ë akõldak). Signi®cant dierences in total oil, fatty acid composition, stability index, a-tocopherol content and mineral composition were observed between varieties. The highest stability index values were observed in commercial Tombul (6.29), FosË a (5.93) and Palaz (5.42) varieties. No signi®cant advantage of new hybrid varieties over commercial varieties was observed in terms of stability of hazelnuts. #
Journal of Food Engineering, 1999
Thin layer drying characteristics of hazelnuts during roasting were described for a temperature r... more Thin layer drying characteristics of hazelnuts during roasting were described for a temperature range of 100±160°C, using ®ve semi-theoretical and two empirical thin layer models. The eective diusivity varied from 2X301 Â 10 À7 to 11X759 Â 10 À7 m 2 /s over the temperature range. Temperature dependence of the diusivity coecient was described by Arrhenius-type relationship. The activation energy for moisture diusion was found to be 1891.6 kJ/kg. Thin layer drying characteristics of hazelnut roasting were satisfactorily described by an empirical Thompson model with the linear temperature dependence. Ó
Journal of Agricultural Engineering Research, 1997
The quality of hazelnuts, sized and cracked by different systems was compared in a commercial pro... more The quality of hazelnuts, sized and cracked by different systems was compared in a commercial processing plant by determining the percentages of nuts that were damaged, broken, left-in the-shell, cracked, unbroken, recyclable, or undamaged. Hazelnuts larger than 16 mm diameter had different cracking behaviour, as compared with smaller ones. In experiments with a traditional Turkish cylindrical sizer and stone cracker
Journal of Food Engineering, 2000
Hazelnut roasting was analyzed using response surface methodology to ®nd out the eect of process ... more Hazelnut roasting was analyzed using response surface methodology to ®nd out the eect of process variables on color development during roasting and to establish prediction models. The roasting temperature was found to be the main factor aecting color development. Developed prediction models satisfactorily described color development as a function of roasting temperature and exposure time for L-value, a-value and b-value of whole-kernel, ground-state and cut-kernel measurements. Whole-kernel measurements were signi®cantly lighter in color compared to ground-state and cut-kernel measurements due to internal browning of the hazelnuts during roasting. The results also indicated that the L-value of ground-state measurements, which take into account internal browning during roasting, should be used to monitor roasting of hazelnuts. Ó
Food Chemistry, 2001
Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated ... more Five new hybrids (T. Kolon, H190, H260, H262, H580) of Turkish hazelnut varieties were evaluated in terms of total oil, fatty acid composition, a-tocopherol, unsaturated/saturated ratio, stability index and mineral in comparison with ®ve commercial Turkish hazelnut varieties (Tombul, Palaz, Mincane, FosË a and C Ë akõldak). Signi®cant dierences in total oil, fatty acid composition, stability index, a-tocopherol content and mineral composition were observed between varieties. The highest stability index values were observed in commercial Tombul (6.29), FosË a (5.93) and Palaz (5.42) varieties. No signi®cant advantage of new hybrid varieties over commercial varieties was observed in terms of stability of hazelnuts. #
Fett-lipid, 1998
The oil content, fatty acid and sterol compositions and other parameters of pistachio nut (Pistac... more The oil content, fatty acid and sterol compositions and other parameters of pistachio nut (Pistacia vera L.) samples corresponding to five different varieties, all cultivated in Turkey were determined. Mean values were 59.69 ± 1.80% for fat content, 0.9143 ± 0.006 for specific ...
Journal of Food Engineering, 2000
Kinetics of color changes during hazelnut roasting was described for a temperature range of 100±1... more Kinetics of color changes during hazelnut roasting was described for a temperature range of 100±160°C for 60 min. The rate of color changes was signi®cantly aected by temperature and time over the experimental conditions. Roasted hazelnut samples produced signi®cantly lower L-value and b-value in ground-state color measurements compared to whole-kernel measurements. The results showed that color changes during hazelnut roasting can be satisfactorily described by a third-degree polynomial with an Arrhenius-type temperature dependence of the model coecients. Activation energy for the L-value of color was found to be 62.3 kJ/mol over the temperature range of the study. A generalized model for color changes during roasting of hazelnuts as a function of temperature and time was established. Ó
Food Chemistry, 2001
Changes in total amino acid composition, thiamine and riboflavin contents, peroxide value and fre... more Changes in total amino acid composition, thiamine and riboflavin contents, peroxide value and free fatty acid contents were determined in roasted Giresun and Akçakoca hazelnuts. The results showed that roasting significantly affected peroxide value, free fatty acids, ...
Drying Technology, 2000
Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during r... more Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10−7 to 21.5×10−7m2/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.