engleski

Ultrasound assisted extraction of green tea (Camellia sinensis)

Products derived from processed tea leaves (Camellia sinensis) have gained a lot of popularity, due to their sensory properties and well documented health promoting and stimulant effects, which stem from the polyphenols present in tea.1 Catechines are the most important group of tea polyphenols (8-15% of dry leaf weight)2. Because of the wide possibility for application of tea catechines in food and cosmetic products, it is very important to devise an efficient extraction technique for these compounds, therefore, different combinations of solvents and high temperature have already been employed. Due to the demand for high throughput, environmentally friendly techniques, other procedures like ultrasonically assisted extraction (UAE), are currently being studied. During extraction, mechanical effect of ultrasound is believed to accelerate the release of organic compounds contained within the plant due to cell wall disruption, mass transfer intensification and easier access of the solvent to the cell content.3 In tissues where prehydration is necessary to achieve extraction and when desired components are located within cells, like in tea leaves (mesophyll cell vacuoles)4, ultrasound treatment is critical for achieving rapid and complete extraction5, 6. Therefore, this study employs different conditions of UAE for water extraction of bioactive compounds from tea. Six different levels of ultrasound power have been applied and compared with control sample, extracted in the same device and under same conditions without application of ultrasound. During each extraction (90 minutes) samples have been taken each 5 minutes and scanned at three different wavelengths (figure 1) to find the optimum extraction time. Extracts obtained at optimum time were also tested for total phenolic content as well as their antioxidant capacity. All samples obtained by UAE showed higher values than control sample in all applied assays.

green tea; catechin; extraction; ultrasound

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