Food Engineering / Gıda Mühendisliği
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Other Sıcaklık ve Sürenin Havuç ve Yeşil Fasulyelerde Bulunan Pektin Metilesteraz Enzimi Üzerindeki Etkisinin Belirlenmesi(Gıda Teknolojisi Derneği, 2003) Yemenicioğlu, Ahmet; Cemeroğlu, BekirHavuç ve yeşil fasulyelerden elde edilmiş ekstrakte ve homojenatlarda PME enziminin aktivite düzeyi ve termal karakteristikleri belirlenmiştir. Yeşil fasulyelerden elde edilmiş homojenatlarda havuçlara kıyasla 2.6 kat daha fazla PME aktivitesi bulunduğu saptanmıştır. Çözünür, iyonik ve kovalent bağlı PME fraksiyonlarının yüzde dağılımı y. fasulyelerde sırasıyla; 3, 88,9 ve havuçlarda 0,81, 19 düzeyinde olduğu belirlenmiştir. Homojenatlarda bulunan PME enzimlerinin optimum sıcaklıkları y. fasulylerde; 40$^circ$C, buna karşın havuçlarda; 50$^circ$C'dır. Her iki sebzede de iyonik olarak bağlı PME enzimleri, benzer termal karakteristiklere sahip olup 40$^circ$C'de optimum aktivite göstermektedir. Buna karşın kovalent bağlı enzim fraksiyonunun optimum sıcaklığı, havuçlarda 55$^circ$C, y. fasulyelerde 50$^circ$C dır.Article Citation - WoS: 153Citation - Scopus: 192Development of Cellulose Acetate Based Antimicrobial Food Packaging Materials for Controlled Release of Lysozyme(Elsevier Ltd., 2009) Gemili, Seyhun; Yemenicioğlu, Ahmet; Alsoy Altınkaya, SacideAntimicrobial packaging materials were obtained by incorporation of lysozyme into cellulose acetate (CA) films. In order to achieve controlled release of lysozyme, the structure of the films was changed from highly asymmetric and porous to dense by modulating the composition of the initial casting solution. The highest release rate, soluble lysozyme activity and antimicrobial activity were obtained with the film prepared from 5% CA solution including 1.5% lysozyme. Increasing CA content in the casting solution decreased the porosity of the films, hence, reduced the release rate, maximum released lysozyme activities and the antimicrobial activities of the films. In contrast, immobilized lysozyme activities and the tensile strength of the films increased. The incorporation of lysozyme did not cause significant reductions in tensile strength and elongation at break values except in films prepared with 15% CA. This study showed the good potential of asymmetric CA films to achieve controlled release in antimicrobial packaging.Article Citation - WoS: 36Citation - Scopus: 38Antimicrobial Activity of Lactoperoxidase System Incorporated Into Cross-Linked Alginate Films(John Wiley and Sons Inc., 2009) Yener, Fatih Yalçın Güneş; Korel, Figen; Yemenicioğlu, AhmetIn this study, the antimicrobial effect of lactoperoxidase (LPS) incorporated alginate films was investigated on Escherichia coli (NRRL B-3008), Listeria innocua (NRRL B-33314), and Pseudomonas fluorescens (NRRL B-253) in presence of different concentrations of H2O2 (0.2, 0.4, and 0.8 mM) and KSCN (1, 2, and 4 mM). The incorporation of 70 nmol ABTS/min/cm2 LPS into alginate films gave 0.66 to 0.85 nmol ABTS/min/cm2 enzyme activity at 0.2 to 0.8 mM H2O 2 concentration range. The antimicrobial activity of LPS system on target bacteria changed according to the concentrations of KSCN and H 2O2. The growth of all tested bacteria was prevented for a 6-h period by applying LPS system in presence of 0.4 or 0.8 mM H 2O2 and 4 mM KSCN. At 0.8 mM H2O2 and 4 mM KSCN, the LPS system also inhibited growth of L. innocua and P. fluorescens for a 24-h incubation period, whereas E. coli growth could not be inhibited for 24 h under these conditions. At 0.2 mM H2O2 and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens. The decreasing order of the resistance of studied bacteria to LPS system is as follows: E. coli, L. innocua, and P. fluorescens. The developed antimicrobial system has a good potential for use in meat, poultry, and seafood since alginate coatings are already used in these products. Further studies are needed to test the LPS incorporated edible films in real food systems.Article Citation - WoS: 115Citation - Scopus: 135Antioxidant Activity and Phenolic Content of Fresh and Dry Nuts With or Without the Seed Coat(Academic Press Inc., 2009) Arcan, İskender; Yemenicioğlu, AhmetTotal antioxidant activities based on ABTS free radical scavenging activity and phenolic content of fresh or dry hazelnuts, walnuts and pistachios assayed with their seed coats changed between 3063 and 11,076 μmol trolox equivalents/100 g d.w. and 256 and 755 mg gallic acid equivalents/100 g d.w., respectively. The walnuts used in this study showed the highest antioxidant activity, followed by pistachios and hazelnuts. The removal of seed coat reduced the total antioxidant activity of hazelnuts, walnuts and pistachios almost 36, 90 and 55%, respectively. The total antioxidant activities of investigated fresh and dry nuts are not considerably different. However, phenolic content and antioxidant activity in hydrophilic and ethanolic fractions obtained by successive extraction of nuts showed some variation. The antioxidant activity in 1-serving portion of fresh or dry walnuts is equivalent to that in almost 2-serving portions of black tea, and 1.2-1.7-serving portions of green and Earl Grey tea. One-serving portions of dry hazelnuts and fresh or dry pistachios contained antioxidant activity equivalent to that in 0.7-1-serving portions of black tea. The antioxidant activity measurements correlated with phenolic content (r2 = 0.70). This study showed the potential of using fresh or dry nuts to develop functional foods with high antioxidant activity.Article Citation - WoS: 86Citation - Scopus: 102Total Antioxidant Activity and Total Phenolic Contents in Different Turkish Eggplant (solanum Melongena L.) Cultivars(Taylor and Francis Ltd., 2009) Ökmen, Bilal; Şığva, Hasan Özgür; Mutlu, Sevgi; Doğanlar, Sami; Yemenicioğlu, Ahmet; Frary, AnneIn this study, total water soluble antioxidant activity and phenolic content of 26 eggplant (Solanum melongena L.) cultivars were investigated. Total water soluble antioxidant activity of the cultivars varied from 2664 to 8247 molTrolox/kg, which is a 3.1-fold difference. Cultivars also showed significant variation for total phenolic contents ranging from 615 to 1376 mg/kg, a 2.2-fold difference. The two traits were significantly correlated and results of this study suggested that breeders can use the information to develop eggplant cultivars with high antioxidant activity.Article Citation - WoS: 14Citation - Scopus: 23Water-Soluble Antioxidant Potential of Turkish Pepper Cultivars(American Society for Horticultural Science, 2008) Frary, Anne; Keçeli, Mehmet Ali; Ökmen, Bilal; Şığva, Hasan Özgür; Yemenicioğlu, Ahmet; Doğanlar, SamiIn this work, 29 pepper cultivars that represent the diversity of types and varieties grown in Turkey were analyzed for water-soluble antioxidant capacity and phenolic and vitamin C contents. In addition, 14 non-Turkish cultivars were tested for comparison. Significant diversity was observed in the different cultivars with the most variation (7.4-fold) seen for total antioxidant capacity, which ranged from 2.57 to 18.96 mmol Trolox/kg. Vitamin C content for the peppers ranged from 522 to 1631 mg·kg-1, a 3.1-fold difference, whereas total phenolic content for the pepper cultivars ranged from 607 to 2724 mg·kg-1, a 4.5-fold difference. When cultivars were grouped by morphology/ use, it was found that some types had significantly more variation and higher antioxidant activities than other types. Thus, for water-soluble antioxidant capacity, most variation was seen in long, blunt-ended Çarliston types, whereas long, pointed Sivri peppers had the highest mean capacity. Bell-shaped Dolmalik and Sivri peppers had the most variation for phenolic content, but fancy Süs and Sivri types had the highest means for this trait. Dolmalik types showed the most variation for vitamin C content, whereas Süs and Sivri peppers had the highest means for this character. All three parameters were significantly and positively correlated with the strongest correlation between total antioxidant capacity and phenolic content (r = 0.71). The presence of significant variation for antioxidant content in Turkish germplasm indicates that this material can be used for improvement and genetic mapping of nutritional content in pepper.Article Citation - WoS: 125Citation - Scopus: 156Antimicrobial and Antioxidant Activity of Edible Zein Films Incorporated With Lysozyme, Albumin Proteins and Disodium Edta(Elsevier Ltd., 2007) Mecitoğlu Güçbilmez, Çiğdem; Yemenicioğlu, Ahmet; Arslanoğlu, AlperIn this study, partially purified lysozyme was incorporated into zein films in combination with chickpea albumin extract (CPAE), bovine serum albumin (BSA) and disodium EDTA. The zein films showed an inherent free radical scavenging activity. Incorporation of lysozyme did not contribute to soluble free radical scavenging activity of zein films. However, the incorporation of lysozyme in combination with CPAE increased the soluble and immobilized free radical scavenging activity of zein films 17% to 25% and almost 84%, respectively. The incorporation of CPAE also improved the distribution of partially purified lysozyme preparation in zein films and enabled the controlled release of lysozyme by reducing its release rate from zein films between 1.5- and 3.5-fold, depending on the concentration of incorporated CPAE. In contrast, the BSA incorporation made distribution of lysozyme more heterogeneous and it did not contribute to the free radical scavenging activity of films significantly. The combinational incorporation of partially purified lysozyme with disodium EDTA · 2H2O or CPAE and disodium EDTA · 2H2O gave zein films effective on Escherichia coli and Bacillus subtilis. This study clearly showed the benefits of using functional protein extracts to control lysozyme distribution and release rate and to improve antioxidant activity in zein films.Article Citation - WoS: 98Citation - Scopus: 118Antioxidant Activity of Protein Extracts From Heat-Treated or Thermally Processed Chickpeas and White Beans(Elsevier Ltd., 2007) Arcan, İskender; Yemenicioğlu, AhmetIn this study, antioxidant activities of water-soluble protein extracts from chickpeas and white beans were investigated. The area under the curve (AUC) values of lyophilized crude protein extracts (dialyzed or undialyzed) from thermally processed (121 °C for 20 min) or heat-treated (90 °C for 20 min) chickpeas (73-91 μmol trolox/g) and white beans (39-67 μmol trolox/g) indicated a higher free radical-scavenging capacity and thermostability for chickpea proteins than for white bean proteins. The thermal processing also increased the Fe+2-chelating capacity of lyophilized chickpea crude protein extracts 1.8-fold whereas it caused a 2.3-fold reduction in the Fe+2-chelating capacity of lyophilized white bean crude protein extracts. Dialysis increased the protein content of lyophilized chickpea extracts 1.5-2-fold but it did not affect the protein content of lyophilized white bean extracts significantly. Ammonium sulfate precipitation was not effective for selective precipitation of antioxidant proteins. However, it improved the free radical-scavenging capacity of lyophilized protein extracts from thermally processed chickpeas and white beans by almost 25% and 100%, respectively. DEAE-cellulose chromatography, indicated the presence of five (A1-A5) and three (B1-B3) antioxidant protein fractions in heat-treated and thermally processed chickpea protein extracts, respectively, and can be used for the partial purification of antioxidant proteins. The results of this study showed the good potential of chickpea proteins as thermostable natural food antioxidants.Article Citation - WoS: 23Citation - Scopus: 26Partial Purification and Preparation of Bovine Lactoperoxidase and Characterization of Kinetic Properties of Its Immobilized Form Incorporated Into Cross-Linked Alginate Films(Elsevier Ltd., 2007) Mecitoğlu, Çiğdem; Yemenicioğlu, AhmetLactoperoxidase (LPS), purified directly from bovine rennet whey by Toyopearl-SP cation-exchange chromatography and lyophilized by using dextran as supporting material, maintained almost 70 and 60% of its activity after almost 2 and 5 months storage at -18 °C, respectively. Incorporation of the prepared LPS into alginate films between 0.08 and 0.69 mg/cm2 (516-4325 U/cm2) caused the immobilization of most of the enzyme and gave films with LPS activity between 0.05 and 2.8 U/cm2, determined in the presence of 8 μM H2O2. Between 2 and 24 μM H2O2 concentrations, a two-fold increase in H2O2 concentration caused 1.5-2.5-fold increase in LPS activity of films incorporated with 0.24-0.28 mg/cm2 (1200 U/cm2) LPS. The Q10 and Ea of immobilized enzyme activity between 4 and 16 °C were 1.69 and 34.6 kJ/mol, respectively. However, in the 16-30 °C range, the temperature change had almost no effect on LPS activity of films. The optimal activity of immobilized LPS was observed at pH 6.0, but the enzyme maintained 30-85% of its activity between pH 3.0 and 7.0. The immobilized LPS also had a high stability between pH 4.0 and 6.0. The results of this study showed the good potential of LPS-incorporated alginate films in forming a natural antimicrobial mechanism in different foods.Article Citation - WoS: 21Citation - Scopus: 29Partial Purification and Kinetic Characterization of Mushroom Stem Polyphenoloxidase and Determination of Its Storage Stability in Different Lyophilized Forms(Elsevier Ltd., 2007) Şimşek, Şebnem; Yemenicioğlu, AhmetMonophenolase (1011 ± 626 U/g AP) and diphenolase activities (5163 ± 3059 U/g AP) of PPO in acetone powders (APs) of different mushroom stems varied considerably. However, the limited variation of average dipenolase (L-DOPA) to monophenolase (L-tyrosine) activity ratio (5.4 ± 0.7) in crude extracts showed the homogeneity of PPO from different mushroom stems. The change in extraction material or partial purification method (ammonium sulfate or acetone precipitation) did not affect the temperature stability, temperature and pH dependency and Km of monophenolase activity considerably. However, some changes were observed in pH stability and substrate specificity of PPO in different parties of mushroom stems. The most important aspects of mushroom stem PPO are its lower diphenolase to monophenolase activity ratio than mushroom cap PPO, low temperature dependency of activity between 25 and 40 °C (Ea = 30 kJ/mol), broad optimum pH between 6 and 8, but lack of activity pH ≤5, and ability to use phloridzin as substrate. The mushroom stem PPOs partially purified and lyophilized by using sucrose, dextran or alginate showed moderate to high stability at -18 °C for 6-6.5 months. Thus, the mushroom stems obtained as a waste material during mushroom processing may be used as a more homogenous source than whole mushrooms to obtain PPO used for different industrial, clinical or research purposes.