Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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Author: search.filters.author.Köseoğlu, OyaLanguage: search.filters.language.en

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 2
    Citation - Scopus: 4
    Identification of Turkish Extra Virgin Olive Oils Produced in Different Regions by Using Nmr (h-1 and C-13) and Irms (c-13/C-12)
    (Wiley, 2023) Sevim, Didar; Köseoğlu, Oya; Ertaş, Hasan; Özdemir, Durmuş; Ulaş, Mehmet; Günnaz, Salih; Çelenk, Veysel Umut
    Isotope ratio mass spectroscopy (IRMS) and nuclear magnetic resonance (NMR) spectroscopy techniques are two of the analytical methods that are used to characterize food products. The aim of this study is to classify extra virgin olive oil (EVOO) samples collected from different regions of Turkey based on H-1 and C-13 NMR spectra along with IRMS d(13)C carbon isotope ratio data by using chemometrics multivariate data analysis methods. A total of 175 EVOO samples were analyzed in 2014/15 and 2015/16 harvest seasons. Multivariate classification and clustering models were used to identify geographical and botanical origins of the EVOOs. IRMS results showed that there was no significant difference in terms of d(13)C values between the years in terms of harvest year (p > 0.05), only extraction phase and variety were statistically significant factors (p < 0.05). The interactions of the factors showed that the harvest year x variety interaction is important. The outcomes of this research clearly indicated that considering the partial least squares discriminant analysis result with NMR spectra, the percent success of the model in the South Marmara, North Aegean, and South Aegean region samples were 95%, 95.7%, and 96.4% in the model set, respectively. The results showed that by using classification and clustering models, geographic marking and labeling of these oils can be carried out regardless of differences in year and production systems (2 and 3 phase extraction system) according the NMR analysis.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 12
    Determination of the Quality and Purity Characteristics of Olive Oils Obtained From Different Regions of Turkey, Depending on Climatic Changes
    (Wiley, 2022) Sevim, Didar; Köseoğlu, Oya; Özdemir, Durmuş; Hakan, Mehmet; Büyükgök, Elif B.; Uslu, Hatice; Dursun, Özgür
    Virgin olive oils (VOOs) obtained from olives grown in different regions of Turkey under changing climatic conditions sometimes show different sensory and chemical properties. This study was planned to determine whether these deviations are due to climatic changes or not. For this purpose, five different olive varieties (Ayvalik, Memecik, Gemlik, Nizip Yaglik, Kilis Yaglik) of commercial importance were harvested from the provinces/districts (four different region) where cultivation is intense during the 2017/2018-2020/2021 harvest years. Every year, olive samples were collected from 3 orchards from 13 provinces/districts. One hundred and fifty-six samples were subjected to the purity, quality and sensory analysis. Basic climatic values (average, minimum and maximum temperature, humidity and precipitation) were examined for four consecutive years. All of the examined olive oil samples were determined within the legal limits in terms of fatty acid composition and fatty acid ethyl ester values. However, delta-7-stigmastenol value from the sterol composition was found to be above 0.5% in some samples in all the years studied (total 21 samples). Delta-7-stigmastenol values of olive oil samples varied between 0.16% and 1.14%. Multiple linear regression analysis was applied using a genetic algorithm-based inverse least squares method to determine whether there is a relationship between climate data and delta-7-stigmastenol values. According to this result, it has been determined that the delta-7-stigmastenol value is high when the annual average relative humidity is low and the annual average temperature is high. There is an urgent need to make forward-looking plans due to climate change.
  • Article
    Determination of Triacylglycerol Composition of Ayvalık and Memecik Olive Oils During Storage by Chemometric Methods
    (Sakarya Üniversitesi, 2017) Köseoğlu, Oya; Sevim, Didar; Özdemir, Durmuş
    The aim of present investigation is to discriminate two important Turkish olive cultivars (Ayvalık and Memecik) by studying their triacylglycerol (TAG) compositions during storage (15 months) taken from different orchard in Ayvalık and Aydın region which have a significant potential for olive oil production in Turkey, during 2009 and 2010 harvest years. Olives were harvested by hand at 2 different maturation indices and processed by an Abencor system. The olive oil samples were stored at room temperature and they were divided into two groups including exposed to diffused daylight and dark for a period of 15 months. Multivariate classification and clustering were done by the application of unsupervised chemometrics methods such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) based on the TAG profiles of the olive oil samples. PCA and HCA analysis of olive oils showed significant differences according to harvest years and cultivars. PCA scores plot showed that the samples were classified into two main groups with respect to harvest years based on the first principal component (PC1). In terms of storage effect, there was no significant change in TAG compositions among the samples from beginning of storage to 15 months of storage regardless of storage conditions (either in dark or in daylight). In addition, PCA scores plot indicated that the samples were also successfully clustered into two sub-groups according to cultivars in both years based on the second principal component (PC2).
  • Article
    Determination of Bitterness Index (k225) and Total Fenol Content of Olive Oils Obtained With Different Regions, Varieties and Processing Systems
    (Ege Üniversitesi, 2018) Köseoğlu, Oya; Sevim, Didar; Dural, Mehmet Ulaş; Özdemir, Durmuş
    In this work the effect of different growing areas on olive (Ayvalık, Memecik, Gemlik, Beylik, Edincik Su, Girit, Kilis Yağlık, Sarı Ulak, Tavşan Yüreği, Topak Aşı) oil bitterness index (K225) were studied at the South Marmara, South and North Aegean, West and East Mediterranean  Regions at two, two and a half (2.5), and three phase extraction system, during 2014/2015 crop season. A total of 41 virgin olive oils samples were collected from these Regions. Total phenol content and bitternes index (K225) were analyzed in the research. A Solid-Phase Extraction procedure were carried out for extraction of the bitter compounds. The results of total phenol content and K225 values showed that the Beylik olive oil was determined with the highest total phenol conent and bitterness index (K225) with 330.26 mg CAE kg-1 oil  and 1.21 at 2.5 phase extraction system from Manavgat at the West Mediterranean Region, respectively. After the Beylik  variety, the highest total phenol content was determined Ayvalık and Edincik Su olive oil with 291.03 and 270.62 mg CAE kg-1 oil, respectively. The Memecik and Ayvalık olive oil bitterness index (K225) was determined 0.86 and 0.85 at two phase extraction system from Muğla and Burhaniye at the South and North Aegean, respectively.