Onur Tolga OKAN
@avesis.ktu.edu.tr
Chemical and Chemistry Processing Technology
RESEARCH, TEACHING, or OTHER INTERESTS
Agricultural and Biological Sciences, Plant Science, Food Science, Forestry
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Mehmet Öz, Ilhan Deniz, Onur Tolga Okan, Cemalettin Baltaci, and Seyda Merve Karatas
Informa UK Limited
Abstract Today, the use of essential oils is increasing day by day, and it is considered as raw materials in many industries. Therefore, this study aims to identify the essential oil profile, antioxidant and antimicrobial activity of Rosa canina L. and Rosa pimpinellifolia L. reveal their potential use in the industry. Essential oils that were obtained in 2013-2014 from different parts (flower, leaf, stem, and fruit) of Rosa canina L. and Rosa pimpinellifolia L. by the hydro-distillation method were analyzed by GC/MS. The dominant components in Rosa canina L. were found as trans-geraniol in the flowers (42.08 % for 2013), linalool in the leaves (11.55 % for 2014), and stem (14.91 % for 2013) and vitispirane in the fruits (37.19 % for 2014). The dominant components in R. pimpinellifolia L. were found as heneicosane in the flowers (22.07 % for 2014), γ-elemene in the leaves (30.21 % for 2013), linalool in the stem (14.76 % for 2013) and the fruits, (E)-2-hexenal for those collected in 2013 (14.09 %). The IC50 and FRAP values of the samples ranged from 127.54 to 142.22 μg/g and 121.43 to 296.78 μmol TE/g, respectively. According to the results obtained, both R. canina L. and R. pimpinellifolia L. were found to show poor antioxidant values of DPPH and FRAP. In general, it was determined that the essential oils obtained from different plant parts of both species had a moderate antimicrobial effect against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, and Pseudomonas aeruginosa.
Sevgi Kolayli, Zehra Can, Hilal Ebru Çakir, Onur Tolga Okan, and Oktay Yildiz
Walter de Gruyter GmbH
Abstract Objective The purpose of this study was therefore to investigate various physicochemical properties, phenolic composition and antioxidant capacities of the oak honey, large quantities of which are produced in the Thrace region of Northwest Turkey. Methods Hunter color values (Lab), optical rotation, electrical conductivity, moisture and ash were measured as physicochemical determinants. Sugar, proline content, mineral, phenolic acids, total phenolic flavonoids contents were evaluated as chemical parameters. Ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging were used as antioxidant determinants. Results The results determined that dark-colored honeys (mean 24.95±8.35 L) have proline levels (649.82±203.90 mg/kg), total phenolic content (TPC) (67.29±13.10 mgGAE/100 g) and total flavonoid content (TFC) (10.14±4.78 mgQE/100 g), a high ratio of fructose/glucose (1.65±0.18). Rutin (11.14±8.50 μg/g), p-coumaric acid (6.97±5.80 μg/g) and protocatechuic acid (6.12±4.39 μg/g) were the major phenolic components, and quercetin was also detected in varying amounts in all samples. Potassium (2523±0.28 mg/kg), calcium (63.40±3.20 mg/kg) and magnesium (38.88±0.65 mg/kg) were the major minerals in the honeys. Conclusion Our results showed that physicochemical properties, phenolic compounds, antioxidant capacity, sugar and mineral contents successfully distinguish the geographical origins of oak honey. These findings will contribute to a more accurate evaluation of oak honey in the literature.
Aysegul Ozer, Sabriye Canakci, Gozde Gocmen, Ilhan Deniz, Huseyin Kirci, Onur Tolga Okan, and Ali Osman Belduz
Universidad del Bio Bio
In present study, single and consecutive applications of xylanase and lignin peroxidase were performed in an XOQP TCF sequence to bleach pine and eucalypts kraft pulp. The consecutive use of Geobacillus sp. strain 71 xylanase and Rhodococcus jostii RHA1 lignin peroxidase was more effective than the single uses. XyzGeo71 treatment (X) indicates a 9.76% and 28.52% reduction in kappa number for pine and eucalypts kraft pulps, respectively. LiPRHA1 treatment (X) showed a 7.88% and 20.9% reduction a in kappa number for pine and eucalypts kraft pulps, respectively. The consecutive treatment of XyzGeo71 and LiPRHA1 (X), however, indicated a 13.67% and 37.2% reduction in kappa number for pine and eucalypts kraft pulps, respectively. The results showed that delignification with the consecutive xylanase and lignin peroxidase treatment was very significant.
Onur Tolga OKAN, İlhan DENİZ, Nurettin YAYLI, İhsan Güngör ŞAT, Mehmet ÖZ, and Gönül HATİPOĞLU SERDAR
University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca
Commercial blueberry production has been a viable industry throughout the world for 95 years; because of blueberry is a good source of antioxidant. Blueberries are especially rich in anthocyanin, a flavonoid with potent antioxidant capacity. The aim of this study was to compare the phenolic quantities, antioxidant activities, anthocyanin, sugar and phenolic compounds of blueberries produced in Turkey with those of similar blueberry varieties produced around the world. As a result of the conducted analysis, the total phenolic content (TPC) amount found in the berries was 77.26-215.12 mg GAE/100 g, the total flavonoid content (TFC) was 30.44-91.69 mg QE/100 g and the total anthocyanin content (TAC) was 43.03-295.06 mg c3-GE/100 g. Examining the antioxidant activities of the berries, DPPH between 1.10-5.65 mg/ml, FRAP between 454.93-36832.96 µmol troloks/100 g, β-Carotene between 40.66-86.48%. It was determined that the natural berries contained much more phenolic compounds and higher antioxidant activity than that of the cultivars The result of HPLC analysis, chlorogenic acid is determined to be the dominant compound in all berries. Furthermore, fructose and glucose are found in all fruits in different quantities while sucrose is found in certain varieties of berries as well. At the end of the performed study the data indicate that wild and cultivars of blueberries are rich sources of antioxidants for local as well international industries importing this fruit for food processing and enormous products.
Ilhan DENiZ, Onur Tolga OKAN, Bedri SERDAR, and Halil İbrahim ŞAHiN
Lukasiewicz Research Network - Poznan Technology Institute
Mehmet Öz, İlhan Deniz, Onur Tolga Okan, and M. Said Fidan
Faculty of Forestry, University of Zagreb
Onur Tolga Okan, Ilhan Deniz, and Sebahattin Tiryaki
Universidad del Bio Bio
The purpose of this study was to develop artificial neural network (ANN) models for predicting the effects of wood species, sodium perborate tetrahydrate (SPBTH) ratio, time, and beating degree on tensile index and brightness in bleaching pulp. Unbleached kraft-AQ bamboo and poplar pulps were exposed to first stage oxygen delignification for bleaching under 0,5 MPa, 3% NaOH and 12% consistency conditions. SPBTH bleaching was then carried out as the final stage. SPBTH bleached pulp was next beaten using two different degrees (55 SR° and 65 SR°). Tensile index and brightness data for training, validation and testing of the models were elicited from these experimental investigations. The models were established using the resulting data. The lowest R2 value was 0,98 among training, testing and validation data sets in the prediction of both tensile index and brightness. The networks therefore explain at least 98% of the experimental data for all data sets. The results indicate that ANN is a useful and effective tool for predicting tensile index and brightness. This study thus describes a novel and alternative approach to predicting tensile index and brightness in bleaching pulp compared to the literature.
Saim ATEŞ, İlhan DENİZ, Hüseyin KIRCI, Celil ATİK, and Onur Tolga OKAN
The Scientific and Technological Research Council of Turkey (TUBITAK-ULAKBIM) - DIGITAL COMMONS JOURNALS
The present study determines the characteristics of bleaching and beating of annual plants and agricultural waste, which constitute important raw material potential for the pulp and paper industry in Turkey. It also examines the effects of this process on several paper properties. Firstly, chemical contents are determined for each raw material and then evaluated for use in the pulp and paper industry. All raw materials studied are found to be suitable for use in the pulp and paper industry, according to the determined chemical content. Secondly, pulp with different properties is obtained and subsequently pretreated with the enzyme xylanase. It is then bleached using the elementary chlorine-free (ECF) method, utilizing the DEpD bleaching sequence, which is both easy to apply and highly effective. The bleaching behavior of each material is then determined. The highest ISO brightness value of 98.3% is obtained using soda-AQ pulps deriving from rye straw. This is followed by wheat straw (92.0%), reed (88.6%), corn stalks (87.6%), and rice straw (87.5%). Each unbleached pulp sample is beaten at a constant 3000 revolutions PFI (9000 rev. for hemp), and changes in freeness properties are determined. The hardest material to beat is hemp fibers, followed by reed, rye, corn, and cotton stalks. The best beatable pulps are rice straw, tobacco, wheat, sunflower, and barley stalks. Paper sheets from both unbleached and bleached pulps are tested.
Ozlem Ozgenc, Onur Tolga Okan, Umit C. Yildiz, and Ilhan Deniz
BioResources
Effects of UV-light irradiation and water spray on the mechanical strength and surface characteristics of untreated and pretreated Scots pine sapwood samples were studied. The specimens were treated with parsley seed oil, pomegranate seed oil, linseed seed oil, nigella seed oil, canola oil, sesame seed oil, and soybean oil. The compositional changes and surface properties of the weathered samples were characterized by Fourier transform infrared (FTIR-ATR) spectroscopy and color and surface roughness measurements. The results showed that all vegetable oils provided lower color changes than the control group after 600 h of exposure in a weathering test cycle. The least color change was found on the Scots pine surface pretreated with pomegranate seed oil. The vegetable oil treatment retarded the surface lignin degradation during weathering, indicating that the surface roughness values of pine wood treated with vegetable oils decreased with irradiation over time compared with those of control samples. The effect of artificial weathering on mechanical strength was determined with a compression strength test. It was observed that the compression strength values of Scots pine samples treated with vegetable oils was higher than that of untreated samples after 600 h of weathering exposure.
Onur Tolga Okan, İlhan Deniz, and İbrahim Yildirim
BioResources
The most prominent environmental problems facing the paper industry are those due to bleaching processes that use chlorine compounds. In this study, totally chlorine free (TCF) bleaching sequences were applied to Phyllostachys bambusoides bamboo unbleached kraft anthraquinone (AQ) pulp, using different conditions with Oxygen (O) delignification and Sodium Perborate Tetrahydrate (SPBTH) stages. The effects of oxygen pressure, SPBTH ratio, and bleaching time were studied to maximize the brightness gain at the lowest viscosity loss. Unbleached kraft-AQ bamboo pulp was applied to first stage oxygen delignification for bleaching with under 5 bar, 3% NaOH, and 12% concentration conditions. Following the chelated bleaching, Sodium Perborate Tetrahydrate (SPBTH) bleaching was carried out as the final stage. The optimum bamboo kraft pulp bleaching conditions were SPBTH level: 4%, MgSO4: 0.5%, Na2SiO3: 3%, bleaching time: 80 min., reaction temperature: 70°C, and concentration: 12%. An overall increase in the physical properties of paper was evident up to an SPBTH level of 4%. When the SPBTH level and bleaching time increased, the kappa number, viscosity, opacity, and yellowness were decreased, but the brightness was increased. Oxygen delignification with chelatation and SPBTH as a bleaching sequence was shown to be a promising alternative to produce high-quality pulp from bamboo for cleaner paper.