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Öğe A comparative study of black mulberry juice concentrates by thermal evaporation and osmotic distillation as influenced by storage(Elsevier Ltd, 2016) Dincer C.; Tontul I.; Topuz A.In the present study, black mulberry juice was concentrated using thermal evaporation and osmotic distillation after clarification and pasteurization. The main quality parameters of the concentrates were comparatively investigated after reconstitution with different storage times and temperatures. The parameters investigated were: color, turbidity, pH, titratable acidity, anthocyanin content, percent polymeric color, antioxidant activity, 5-hydroxymethylfurfural (HMF) content and volatile profile. The anthocyanin content, volatile content and turbidity values of osmotically distillated samples were found to be higher than those of the thermal concentrates. Neither HMF nor furfural was detected in the samples soon after the processing; however, levels of process contaminants were found to increase gradually throughout the storage period in both concentrates. Thermal evaporation resulted in markedly higher HMF and furfural formation in comparison to the osmotic distillation process. The anthocyanin content and antioxidant activity of the concentrates decreased, whereas polymeric color ratio and turbidity values increased within longer storage time and higher storage temperature. Industrial relevance Concentration is one of the key steps affects the chemical and physical properties of black mulberry juice since black mulberry phytochemicals, mainly anthocyanins, are labile to heat treatment and storage. Thermal evaporation has some drawbacks such as loss of fresh juice flavors, color degradation, reduction of nutritional value and formation of mutagenic compounds such as HMF and furfural. These drawbacks require alternative methods that involve minimal processing. Osmotic distillation can be recommended for black mulberry juice concentration in order to preserve its heat-sensitive components and to produce high-quality product. © 2016 Elsevier LtdÖğe 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.Öğe 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 (Öğe 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
