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    Comparative study on volatile compounds in Turkish green tea powder: Impact of tea clone, shading level and shooting period
    (2013) Tontul I.; Torun M.; Dincer C.; Sahin-Nadeem H.; Topuz A.; Turna T.; Ozdemir F.
    The objective of this study was to determine volatile compounds in green tea powders produced from a clone of two different teas (Camellia sinensis (L.) O. Kuntze) grown under different shade levels and harvested in two consecutive shooting periods. Both hydrodistillation and solid phase microextraction (SPME) methods were comparatively performed to identify maximum number and amount of volatile compounds. SPME method enables the identification of the greatest number of volatile compounds which principally comprise limonene, ?-terpineol and heptanal. A few specific volatile compounds were identified for differentiation of green tea samples depending on the treatments, such as, heptanal in 1st shooting period, ethyl benzene, xylene and benzenacetal for 2nd shooting period, and phytol and tridecane for shading treatments. The treatments were significantly clustered either as tea clones or shooting period by the volatile compounds i.e. linalool, ?-terpineol, 3-methylbutanal, 2-methylbutanal and p-cresol, 2,6-di-tert-buthyl determined in hydrodistillation method and tridecane, heptanal, linalool, nonanal, hexanal, ?-terpineol, 1-pentanol, pentanal, dimethylsulfide, 2,2,4-trimethylhexane, limonene and 1-hexanol in SPME method as shown by principal component analysis (PCA). © 2012 Elsevier Ltd.
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    Influence of microwave, the combined microwave/hot air and only hot air roasting on the formation of heat-induced contaminants of carob powders
    (Taylor and Francis Ltd., 2018) Gunel Z.; Tontul İ.; Dincer C.; Topuz A.; Sahin-Nadeem H.
    This study aims to investigate the effects of microwave, combined microwave/hot air treatment and hot air-only roasting on the formation of heat-induced contaminants of carob powders. Moisture content, water activity and pH values of the product decreased with the increasing roasting time and microwave power, while browning index (BI) and ultraviolet absorbance (UV-A) values were increased. While L and b values of carob powders decreased with increasing the roasting time and microwave power, a and ?E values were increased. Varying roasting conditions also significantly affected the content of Maillard reaction products (MRPs): 5-hydroxymethylfurfural (HMF) (0.69–28.32 mg/kg dry matter), furfural (
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    Phenolic composition and antioxidant activity of Sideritis lycia and Sideritis libanotica subsp. linearis: Effects of cultivation, year and storage
    (Elsevier GmbH, 2017) Dincer C.; Torun M.; Tontul I.; Topuz A.; Sahin-Nadeem H.; Gokturk R.S.; Tugrul-Ay S.
    Flowered verticillasters of Sideritis lycia Boiss. & Heldr. and Sideritis libanotica Labill. subsp. linearis (Benth.) Bornm. are used as herbal tea. In the present study, these plants were tried to be cultivated and phenolic composition and antioxidant activity of the wild and cultivated plants were compared. Total phenolics, flavonoids and antioxidant activity of S. lycia and S. libanotica subsp. linearis were found in the range of 16.05–18.04 and 9.16–10.49 g gallic acid equivalent/kg dw, 9.70–14.30 and 5.41–9.68 g catechin equivalent/kg dw and 6.57–8.71 and 13.88–19.04 g dw/g DPPH, respectively. Total flavonoid content and antioxidant activity of the wild plants were determined to be higher than cultivated samples. Major phenolic acids were p-coumaric, caffeic and ferulic acids, while the main flavonoids were quercetin, morin and apigenin. Consecutive harvesting year and storage period did not cause remarkable differences on the analysed parameters, in general. Phenolic compounds of the both plants were decreased during storage, in general. © 2016 Elsevier GmbH