Browsing by Subject "WATER EXTRACTION"

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    Optimisation of microwave effect on bioactives contents and colour attributes of aqueous green tea extracts by central composite design
    (SPRINGER) Taskin, B; Özbek, ZA
    The aim of the present study was to investigate the effects of microwave-assisted extraction parameters on total phenolic content (TPC), total flavonoid content (TFC), condensed tannins content (CTC), DPPH-scavenging activity, and colour attributes of aqueous green tea extracts and to optimise the microwaving conditions using response surface methodology. Microwave power (120-360-600 W) and irradiation time (1-3-5 min) were selected as independent variables. Statistical analysis revealed that all responses were significantly affected by extraction parameters. The optimum microwave-assisted extraction conditions were 350.65 W microwave power and 5 min irradiation time to maximise TPC, TFC, CTC, DPPH-scavenging activity, and L* values and to minimise a* and b* values of aqueous green tea extracts. The predicted TPC was 116.58 mg gallic acid equivalents/g (GAE/g), TFC was 49.33 mg catechin equivalents/g (CE/g), CTC was 9.89 mg catechin equivalents/g (CE/g), DPPH-scavenging activity (IC50) was 294.46 mu g/mL, L* value was 12.31, a* value was 2.61 and b* value was 7.02 under optimum microwave-assisted extraction conditions. This study revealed that microwave extraction conditions should be controlled to obtain aqueous green tea extracts with both high bioactivity and acceptable colour quality.
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    Multi-walled carbon nanotube modified glassy carbon electrode as curcumin sensor
    (SPRINGER WIEN) Cittan, M; Altuntas, E; Çelik, A
    A facile and efficient voltammetric sensing platform was described for curcumin analysis based on the adsorptive stripping voltammetry using multi-walled carbon nanotube modified glassy carbon electrode. As a result of the open-circuit accumulation of curcumin on the fabricated electrode surface, the described analytical procedure was shown to be a sensitive technique for curcumin analysis by increasing the sensitivity of the glassy carbon electrode. A good linear calibration curve in the range of 0.010-5.000 mu M (R-2 = 0.9967) was obtained. The repeatability of the methodology was quite satisfactory. The detection and quantification limits were found as 0.005 and 0.014 mu M, respectively. The methodology was successfully applied to determine the curcumin equivalent in a turmeric extract following the ultrasound-assisted extraction of a turmeric powder. The ultrasound-assisted extraction had a good recovery value between 103.5 and 106.0%. The described methodology would be a facile, sensitive, and cheap alternative to the current methods for curcumin analysis. [GRAPHICS] .