Phd Degree / Doktora

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Effect of Harvest Time, Malaxation Tempetature and Olive Variety on the Chemical Characteristics of Olive Oils
(Izmir Institute of Technology, 2016) Jolayemi, Olusola Samuel; Tokatlı, Figen; Özen, Fatma Banu
Changes in chemical and quality characteristics of olive oils were evaluated with respect to pre and post-harvest factors such as: olive type, harvest time, malaxation temperature, and storage at room temperature. Additionally, discriminative and predictive capacities of UV-vis, near infrared (NIR), mid infrared (MIR) spectra and electronic nose data on olive oils by using multivariate statistical tools were studied. Varietal and harvest time differences were the most significant factors influencing the quality and chemical properties of Ayvalik and Memecik olive oils. Malaxation temperature was significant on a number of phenolic compounds such as tyrosol, hydroxytyrosol and pinoresinol, and peroxide value. Olive oils of early and mid-harvest were higher in phenolic alcohols, and pigments content, whereas peroxide values, linoleic and stearic acids characterized late harvest oils. Storage for 15 months at room temperature in dark facilitated evolution of some important phenols, while increasing the content of ethyl and methyl esters at varying degrees among varieties. There were no significant changes in fatty acids and acidity contents of the oils. However, total phenol content and oxidative stability declined and a significant depletion of colors and pigments contents occurred. Multivariate regression analysis indicated that lipid-based variables are the most consistent contributors (positive or negative) to olive oil oxidative stability. UV-vis, MIR, NIR spectroscopies and e-nose data were excellent varietal and harvest season discriminating tools. Pigments were well predicted by UV-vis, while MIR performs better in the prediction of fatty acids, alkyl esters, oxidative stability and free fatty acid.
Characterization and Classification of Wines From Grape Varieties Grovn in Turkey
(Izmir Institute of Technology, 2014) Şen, İlknur; Tokatlı, Figen
The wines of Turkish grapes from four vintages (2006-2009) were classified according to variety, geographical origin and vintage based on their chemical composition (element, polyphenol, color, acid, sugar, alcohol, pH, total phenol and brix) by using multivariate statistical techniques. In the varietal classification of red wines, the partial least square-discriminant analysis (PLS-DA) demonstrated the discrimination of Boğazkere-Öküzgözü, Kalecik Karası, Syrah and Cabernet Sauvignon varieties from each other as the significant element, polyphenol, organic acid, sugar and alcohol parameters were combined in the model. Boğazkere and Öküzgözü wines of East Anatolia were characterized with their high coumaroylated anthocyanin derivatives, while Syrah wines of West Anatolia were rich in anthocyanins and flavonols. Kalecik Karası wines were the poorest in terms of total phenol content. In the classification of white wines, Emir wines of Kapadokya region were characterized with their high Li, Sr and resveratrol contents. Sultaniye wines were the lowest in polyphenol content and Muscat wines were the richest in hydroxycinnamic acids. The regional discrimination of red and white wines was achieved with the significant element and polyphenol compositions. The western region wines were characterized with their higher Pb content which may be due to the industrialization of West Anatolia. Moreover, red wines of Tekirdağ region were recognized with their low flavonol-glycoside contents. 2009 vintage red wines were characterized with their high anthocyanin and flavonol contents. In the same way, 2009 vintage white wines had higher flavonols, flavonol-glycosides, phenolic acids and flavan-3-ols.

Phd Degree / Doktora

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