Demirbüker Kavak, Dilek
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Demirbüker, D.
Kavak, Dilek Demirbuker
Kavak, Dilek Demirbüker
Demirbuker, D
Demirbuker Kavak, Dilek
Demirbüker, D
Demirbuker, D.
Kavak, Dilek Demirbuker
Kavak, Dilek Demirbüker
Demirbuker, D
Demirbuker Kavak, Dilek
Demirbüker, D
Demirbuker, D.
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03.08. Department of Food Engineering
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Former Staff
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Sustainable Development Goals
1NO POVERTY
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2ZERO HUNGER
2
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3GOOD HEALTH AND WELL-BEING
3
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4QUALITY EDUCATION
1
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5GENDER EQUALITY
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6CLEAN WATER AND SANITATION
2
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7AFFORDABLE AND CLEAN ENERGY
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8DECENT WORK AND ECONOMIC GROWTH
1
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
2
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10REDUCED INEQUALITIES
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11SUSTAINABLE CITIES AND COMMUNITIES
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
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13CLIMATE ACTION
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14LIFE BELOW WATER
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15LIFE ON LAND
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
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17PARTNERSHIPS FOR THE GOALS
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2
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19
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This researcher does not have a WoS ID.
Scholarly Output
9
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6
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7724/4703
Supervised MSc Theses
1
Supervised PhD Theses
1
WoS Citation Count
80
Scopus Citation Count
113
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0
WoS Citations per Publication
8.89
Scopus Citations per Publication
12.56
Open Access Source
9
Supervised Theses
2
| Journal | Count |
|---|---|
| Journal of Food Science | 2 |
| 14th National Biomedical Engineering Meeting, BIYOMUT 2009 | 1 |
| Journal of Molecular Catalysis B: Enzymatic | 1 |
| Journal of Porous Materials | 1 |
| Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi | 1 |
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Article Citation - WoS: 1Orta Nemli İncirlerde Depolama Sonrasında Pektin Metil Esteraz Aktivitesi Değişimi(Pamukkale Üniversitesi, 2015) Demirbüker Kavak, Dilek; Yemenicioğlu, AhmetOrta nemli meyveler, kurutulmuş meyvelerin rehidre edilmesiyle elde edilebilmektedirler. Kuru meyvelere kıyasla doğrudan tüketime daha uygun olan orta nemli meyveler, sanayide unlu mamüller, süt ürünleri, şekerlemeler kullanılabilmektedirler. Bu çalışmanın amacı orta nemli hale getirilmiş incirlerin 3 aylık depolama süresi sonucunda mikrobiyal stabilitelerinin ve dokuda yumuşamaya neden olan pektin metil esteraz enzimi (PME) aktivitelerinin kıyaslanmasıdır. Bu amaçla kuru incirler 30°C ve 80°C'de suyla %30 nem içeriğine ulaşana kadar rehidre edilmişlerdir. Rehidre edilmiş örnekler, 3 ay süreyle +4°C'de depolanmışlardır. Depolama süresi sonunda toplam canlı sayımı sonuçlarına göre 30°C kontrol örnekleri ile 80°C'de rehidre edilmiş örnekler arasında istatistiksel olarak anlamlı bir fark bulunmamıştır. Depolama süresi sonucunda PME aktivitesi, kontrol örnekleri için 24.1 ?mol COOH dk-1g-1 iken, 80°C'de rehidre edilmiş orta nemli incirlerde 17.4 ?mol COOH dk-1g-1bulunmuştur. Sonuç olarak incirleri orta nemli hale getirmek için 80°C'de gerçekleşen rehidrasyon işlemi, depolama sonrası mikrobiyal yükü belirgin şekilde etkilememesine karşın, yumuşamaya neden olan PME aktivitesini 30°C'de rehidre edilmiş kontrol örneklerine kıyasla %28 oranında azaltmaktadır.Article Citation - WoS: 10Citation - Scopus: 12Effects of Hot Rehydration in the Presence of Hydrogen Peroxide on Microbial Quality, Texture, Color, and Antioxidant Activity of Cold-Stored Intermediate-Moisture Sun-Dried Figs(John Wiley and Sons Inc., 2005) Demirbüker Kavak, Dilek; Arcan, İskender; Tokatlı, Figen; Yemecioğlu, AhmetPectin methylesterase (PME) causes considerable softening in intermediate-moisture (IM) figs rehydrated at 30°C and cold stored at 28% to 29% moisture content. Rehydration of figs at 80°C for 16 min inactivated PME partially (25-30%), but this did not prevent the softening over 3 mo of cold storage. Also, heating did not reduce the microbial load of figs significantly and increased their browning. In contrast, rehydration of figs 1st in 2.5% H2O2 at 80°C for 8 min and then in water at 80°C for 8 min reduced the microbial load of IM figs significantly, turned their brown color to yellow-light brown, and maintained their desired textural properties. The residual H2O2 in IM figs decomposed in 3 or 1.5 wk by the in situ catalase or by application of the iron (II) sulfate-ascorbic acid residue elimination method, respectively. Hot rehydration did not affect the antioxidant activity of IM figs, but treatment of figs with H2O2 increased their antioxidant activity slightly. These results indicate that the hot rehydration of figs in the presence of H 2O2 and cold storage may be applied to obtain safe and SO2-free light-colored IM fig products.Article Citation - WoS: 42Citation - Scopus: 60Pistacia Terebinthus Extract: as a Potential Antioxidant, Antimicrobial and Possible Ss-Glucuronidase Inhibitor(Elsevier Ltd., 2010) Demirbüker Kavak, Dilek; Altıok, Evren; Bayraktar, Oğuz; Ülkü, SemraIn this study, inhibition of Escherichia coli glucuronidase (GUS) by a plant extract of Pistacia terebinthus was investigated. P. terebinthus (from Karaburun region in Turkey) leaf extract exhibits various bioactivities, such as antioxidant, antimicrobial and cytotoxic property because of its flavonoid, phenolic and alkaloid contents. HPLC analyses were performed to evaluate the composition of the extract and main flavonoid compounds such as luteolin, luteolin-7-glucoside and apigenin-7-glucoside were detected in extract. GUS activity and kinetic data of the GUS were obtained by measuring rate of production of resulting fluorescent 4-methylumbelliferone (4-MU) and phenolphthalein fluorometrically and spectrophotometrically, respectively. Plant leaves showed higher antioxidant capacity as 85 TEAC (trolox equivalent antioxidant capacity) value and higher antimicrobial activity towards Staphylococcus aureus. 92.4% GUS enzyme inhibition was achieved with 8.3 μg ml-1 crude extract concentration, where IC50 value was found as 2.1 (±0.2) μg ml-1. Kinetic studies by nonlinear regression revealed that inhibition type caused by plant extract was mixed type (noncompetitive and competitive together). Km and Vmax values were 96.94 ± 9.68 nM and 7.81 ± 0.16 nmol min-1 mg-1, respectively. Inhibition constant (αKi) was found as 7.00 ± 0.93 nM having α value 2.17 ± 0.93. Our results may provide useful information regarding the inhibition of microbial GUS activity, preventing deglucuronidation and reducing possible cancer risk by bioactive P. terebinthus crude extract. © 2010 Elsevier B.V. All rights reserved.Doctoral Thesis Inhibition of Microbial Ss-Glucuronidase by Natural Zeolites and Their Effects on Cancer Prevention in Human Intestinal Systems(Izmir Institute of Technology, 2010) Demirbüker Kavak, Dilek; Ülkü, SemraBacterial β-glucuronidase (GUS) enzyme has an important role in the production of reactive metabolites related to some diseases and cancer development. In this thesis, health promoting role of clinoptilolite rich zeolite mineral was proposed to act as a potential inhibitor and as adsorbant of GUS and also to have cytotoxic effect towards cancer cells. Therefore inhibition and adsorption mechanism of GUS by clinoptilolite rich mineral and its cytotoxicity towards cancer cells were investigated. Additionally, another potential inhibitor; casein and their interactions with GUS and clinoptilolite rich mineral were revealed. Results showed that GUS activity was inhibited by either casein or clinoptilolite rich mineral and both of them acted as mixed type inhibitors. Additionally, it was found that clinoptilolite rich mineral was a potential adsorbent for GUS. Results showed that removal percentages of proteins were 9.4-54.4 % and 36.5-77.3 % for GUS and casein, respectively and depended on their initial concentrations. Equilibrium studies showed that both adsorptions were exothermic and physical and kinetic models implied that external fluid film or skin resistance, and intraparticle diffusion might be effective for GUS and casein adsorption, respectively. In cytotoxicity tests, clinoptilolite rich mineral (25mg/ml) inhibited approximately 50 % of the Caco-2 cell proliferation. This high inhibition was not observed for MCF-7 cells where inhibition was found to be 20-30 %. Flow cytometric results for both cell lines indicated that total apoptosis percentage in overall population was low compared to control sample. This result was also confirmed by cell cycle analyses.Master Thesis Control of Microbial and Enzymatic Changes in Intermediate Moisture Sun-Dried Figs by Mild Heating and Hydrogen Peroxide Disinfection(Izmir Institute of Technology, 2003) Demirbüker Kavak, Dilek; Yemenicioğlu, AhmetDuring cold storage, the enzyme pectin methylesterase (PME) caused softening and lossof desired gummy texture in rehydrated intermediate moisture (IM) sun-dried figs. Heat inactivation studies indicated that the purified PME can be inactivated rapidly at 80 o and 90 oC. However, at or below 70 oC the enzyme showed activation by heating and inactivated very slowly. The in-situ activation of PME occurred much more extensively when sun-dried figs were rehydrated between 70o and 90 oC to produce IM figs with approximately 30 % moisture and this prevented the effective inactivation of enzyme even by rehydrations conducted at 80 o and 90 oC. The partial reduction of PME enzyme activity (almost 30 %) by rehydration of figs at 80 oC for 16 min may be used to delay undesirable textural changes in cold stored IM figs for 3 months. However, for longer storage periods hot reyhdration alone is not sufficient to prevent softening. No considerable yeast and mold growth was detected in IM figs cold stored 3-3.5 months.However, in some samples rehydrated in water at 80 oC, the total mesophilic aerobic counts and total yeast and mold counts showed a considerable increase when storage time exceeded 3-3.5 months. The rehydration of IM figs in 2.5 % H2O2 for 16 min at 80 oC reduced the total mesophilic aerobic microbial count of figs almost 90 %. Due to bleaching caused by H2O2, the brown fig color turned to a desirable and stable yellowlight brown as well. However, during cold storage the O2 gas released due to the decomposition of H2O2 by in situ fig catalase, accumulated within figs and caused some physical defects. Also, the residual level of H2O2 in the homogenates of disinfected figs was too much (300 ppm) and it seemed unlikely to eliminate this amount of H2O2 by physical or chemical means during processing. Pureeing IM figs eliminated residual H2O2 very rapidly. The application of rehydration first in 2.5 % H2O2 solution at 80 oC for 4 or 8 min and then in hot water at the same temperature for 12 or 8 min, respectively, also reduced the amount of residual H2O2 in IM figs considerably.Besides, these two-stage rehydration procedures eliminated the physical defects occurred in IM figs due to O2 gas release and gave firmer IM figs. To reduce the initial microbial load of IM figs, 4 and 8 min disinfections conducted in H2O2 solutions were less effective than 16 min disinfection in H2O2 solution. However, both 4 and 8 min disinfections effectively suppressed microbial load for at least 3.5 months and they may be used in the production of SO2 free light colored fig products.Article Citation - WoS: 8Citation - Scopus: 7Potential Application of Hot Rehydration Alone or in Combination With Hydrogen Peroxide To Control Pectin Methylesterase Activity and Microbial Load in Cold-Stored Intermediate-Moisture Sun-Dried Figs(John Wiley and Sons Inc., 2004) Demirbüker Kavak, Dilek; Şimşek, Şebnem; Yemenicioğlu, AhmetSun-dried figs contain a considerable amount of pectin methylesterase (PME) activity (22 μM COOH/ min/g). The enzyme causes softening and loss of desired gummy texture in cold-stored intermediate-moisture (IM) sun-dried figs brought to a 28% to 29% moisture range. Partial reduction of PME activity (28%) delayed undesirable textural changes in IM figs rehydrated at 80°C for 16 min. The heat treatment did not cause a considerable reduction in microbial load. However, the addition of 2.5% H2O2 to the rehydratlon medium at 80°C reduced the initial total mesophilic aerobic count of figs by at least 90% and turned the figs from a brown color to a desirable and stable yellow-light brown. The in situ fig catalase remains after rehydration at 80°C. Thus, by reducing the contact period of figs with H2O2 or by pureeing figs, it is possible to eliminate residual H2O2 and to obtain safe and SO2-free light-colored fig products.Article Citation - WoS: 14Citation - Scopus: 25Kinetic and Equilibrium Studies of Adsorption of Ss-Glucuronidase by Clinoptilolite-Rich Minerals(Elsevier Ltd., 2015) Demirbüker Kavak, Dilek; Ülkü, SemraThe adsorption of the bacterial β-glucuronidase (GUS) enzyme, which is thought to be responsible for the production of reactive metabolites related to some diseases and cancer development, by clinoptilolite-rich mineral was investigated. Batch experiments were performed to analyze of the effects of the clinoptilolite amount and particle size, initial GUS concentration, shaking rate, pH and temperature on the adsorption equilibrium and kinetics. Adsorption equilibrium data were interpreted in terms of Langmuir and Freundlich isotherms; and they were well represented by the Langmuir isotherm model. The percentage of GUS removal by the clinoptilolite-rich mineral was changed in the range of 9.4-54.4% depending on its initial concentration. The kinetic data were analyzed using external film diffusion, intraparticle diffusion, pseudo-first-order and pseudo-second-order models and both external film and intraparticle diffusion appeared to be effective in GUS adsorption. Thermodynamic studies indicated that GUS adsorption is exothermic, physical and spontaneous at the temperatures investigated (288-310 K)Conference Object Citation - Scopus: 1Yapay Sindirim Sıvısında Doğal Zeolitlerde Meydana Gelen Morfolojik Değişmeler(Institute of Electrical and Electronics Engineers Inc., 2009) Demirbüker Kavak, Dilek; Özçelik, Serdar; Ülkü, SemraDoğal zeolitler biyoaktif maddelerdir. Doğal zeolitlerin hayvanlarda biyokütle arttırıcı besi katkı maddesi, insanlarda ülser tedavisinde mide asitliğini tamponlayıcı, asitliği düşürücü ilaç gibi değişik kullanım alanları mevcuttur. Değişik sağlık alanlarında kullanımlarından dolayı, zeolitlerin yapısal stabilitesinin sindirim sırasında belirlenmesi; olası olumlu veya olumsuz etkileşimleri anlamak açısından önem taşımaktadır. Gerçekleştirilen araştırmada, yapay sindirim sırasında zeolitte meydana gelebilecek olası morfolojik değişimlerin incelenmesi hedeflenmiştir. Bu amaçla zeolitin ABTS ile radikal sönümleme kapasitesi araştırılmış, yapay sindirim denemeleri gerçekleştirilerek de uygulama süreci sonrası yapıda olası değişimler ve adsorpsiyonlar taramalı elektron mikroskobu, FTIR, XRD analizleri ile incelenmiştir. 3g/100ml zeolitin ABTS radikalini %45 inhibe ettiği bulunmuştur. Taramalı elektron mikroskobu deneyleri sonucunda yapay sindirilmiş örneklerin yüzey morfolojisinde değişim gözlenmemiştir. Element analizleri yapısal kaybın olmadığını, Al ve Si elementlerinin ağırlıkça yüzdelerinin, kontrol örnekleriyle (Al:8.1; Si: 39) sindirilmiş örneklerde (Al:8.2; Si: 38.3) yaklaşık aynı olduğunu göstermiştir. Infrared spektrum (IR) ve X-ray ışını kırınımı analizleri sonuçları ise bu bulguları doğrulamıştır. Ayrıca taramalı elektron mikroskobu ve IR spektrum sonuçları yapay sindirim ortamındaki maddelerin, zeolit yüzeyinde adsorplanmadıklarıını göstermektedir. Sonuç olarak doğal zeolitler, yapay sindirim sırasında yapısal stabilitelerini kaybetmemektedirler.Article Citation - WoS: 5Citation - Scopus: 8Investigation of Structural Properties of Clinoptilolite Rich Zeolites in Simulated Digestion Conditions and Their Cytotoxicity Against Caco-2 Cells in Vitro(Springer Verlag, 2013) Kavak, Dilek Demirbüker; Ülkü, SemraThe use of the clinoptilolite rich natural zeolites in biomedical applications such as in anticancer therapy, drug or drug support systems and as nutritive supplement is highly dependent on their behavior in digestive conditions. Aim of this study is to investigate structural stability of clinoptilolite rich natural zeolites in simulated digestion conditions and their interactions with digestive media and with Caco-2 (human colon adenocarcinoma) cells. X-ray Diffraction (XRD), Fourier Transform InfraRed (FTIR), Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) analyses of the clinoptilolite rich zeolite samples showed that zeolites preserved their structural stabilities during in vitro digestion. Slight interactions were detected in UV measurements of the digestive liquid media and FTIR spectra of the intestinal digested media powders. SEM results implied that zeolites might have a role in the aggregation of the digestive enzymes. Cytotoxicity test using colon cancer cells showed that clinoptilolite rich natural zeolites have cytotoxic effect against Caco-2 cells and cytotoxicity did not significantly change with respect to simulated digestion process.