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    Effects of Filtration on the Quality Properties of Extra Virgin Olive Oils during Storage
    (Wiley, 2019) Koseoglu, Oya; Sevim, Didar; Kadiroglu, Pinar
    In this study, the effects of filtration on quality parameters, chemical characteristics, antioxidant activity, and oxidative stability (OS) of Turkish olive oils during the storage period of 12 months were investigated. The olive oil free acidity (% oleic acid per 100 g of olive oil) (free fatty acidity, FFA), peroxide values (PV) (meq O-2 kg(-1) oil), and UV spectrophotometric indices (K-232 and K-270 measurements) were used for evaluating the quality parameters of olive oils. alpha-tocopherol analysis, total phenolic content (TPC), total chlorophyll and carotenoid analyses, and 2,2-diphenyl-1-picrylhydrazyl (DPPH center dot) radical-scavenging activity (RSA) assays were carried out. Chromatographic methods were applied to determine the fatty-acid and triacylglycerol (TAG) composition, the content of methyl and ethyl esters (FAEE and FAME), and the content of fatty acids of olive oils. Univariate and multivariate statistical methods were performed to evaluate results. Univariate data analysis results showed that filtration of Ayvalik, Memecik, and Domat olive oils had no considerable influence on quality parameters, antioxidant compounds, FAEE and FAME, antioxidant activity, and OS, except TPC (P < 0.05). A significant difference between the samples was determined regarding storage times of the olive oils. Principal component analysis (PCA) analysis revealed that olive oils were grouped according to storage periods of the olive oils regarding fatty-acid and triacylglycerol (TAG) composition while there was no clear separation among the samples according to the filtration process. However, qualitative and quantitative changes took place on minor and major components of olive oils during the storage period.
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    Oxidative stability of olive oils with supercritical carbon dioxide extracts of olive leaf
    (Innovhub Ssi-Area Ssog, 2022) Sevim, Didar; Koseoglu, Oya; Pazir, Fikret; Ova, Gulden; Kadiroglu, Pinar; Alper, Yuksel
    In this study, quality parameters and oxidative stability of olive oils added with olive leaf (OL), an agricultural by-product extracted by the supercritical carbon dioxide (SCD) method, were evaluated. The SCD OL extraction method was applied at 100 degrees C, 100 bar and 80 minutes. Extracts containing phenolic substances obtained from olive leaves were added to refined olive oil (ROO) (E) at concentrations of 350 (A), 200 (B), 150 (C) and 60 mg CAE/kg oil (D). Olive oil samples were stored in clear glass bottles for 12 months under light (L) and dark (D) conditions. Samples were analysed at 0, 3, 6, 9 and 12 months of storage period. The results of the analyses revealed that the amount of free fatty acid values (FFAV), peroxide value (POV), total phenolic content (TPC), chlorophyll (TChl) and carotenoid (TCar) content and oxidative stability index (OSI) increased as the olive leaf extract (OLE) addition ratio increased. When the effect of OLE concentration on the amount of a- tocopherol was examined, it was determined that the amount of a- tocopherol was higher in ROO (E) and this amount decreased with the addition of OLE. In the samples which OLE was added, odours like alcohol, henna and dried herbs were detected as a result of sensory analysis. Principal component analyses (PCA) indicated that olive oils were discriminated clearly based on the concentrations of OLEs. As a result, it was determined that the TPC, TChl and TCar content and OSI values were the highest in the A sample, which was stored in the dark and had the highest OLE content. Sample A, which is rich in antioxidant components, can be said to be the best example enriched with OLE, apart from sensory properties. In terms of the content of AT, which is equivalent to vitamin E, we can say that the E sample stored in the dark has the best properties except for the sensory properties.
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    Öğe
    Quality characteristics and antioxidant properties of Turkish monovarietal olive oils regarding stages of olive ripening
    (Elsevier Sci Ltd, 2016) Koseoglu, Oya; Sevim, Didar; Kadiroglu, Pinar
    The aim of this study was to discriminate the extra virgin olive oils (EVOO) based on quality characteristics, chemical composition and antioxidant activity according to ripening stages of olives. Two different olive varieties (Memecik and Gemlik) were obtained at different stages of ripening based on skin color (green, purple and black). Quality properties of olive oils; free fatty acidity, peroxide value, K-232 and K-270, purity properties; fatty acid and triacylglycerol (TAG) composition and antioxidant compounds like total phenol, carotenoid and chlorophyll content and antioxidant activity (oxidative stability, ABTS radical scavenging activity) analyses were performed. Higher amount of oleic, linoleic and palmitic acids were observed in olive oils. Oleic acid amount of olive oils decreased, linoleic acid increased with ripening. The most abundant TAG of olive oils were ECN 48, OOO, SLO + POO, ECN 46 and LOO/PLO. Olive oils were clearly classified by principal component analysis based on fatty acid and TAG composition. (C) 2016 Elsevier Ltd. All rights reserved.