Optimization of ultrasound assisted extraction of functional ingredients from Stevia rebaudiana Bertoni leaves
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Faculty of Agriculture, University of Zagreb, Svetošimunska cesta 25, Zagreb, Croatia
Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, Croatia
Publication date: 2015-03-30
Int. Agrophys. 2015, 29(2): 231-237
The aim of the present study was to reveal an effective extraction procedure for maximization of the yield of steviol glycosides and total phenolic compounds as well as anti­oxidant activity in stevia extracts. Ultrasound assisted extraction was compared with conventional solvent extraction. The examined solvents were water (100°C/24 h) and 70% ethanol (at 70°C for 30 min). Qualitative and quantitative analyses of steviol glycosides in the extracts obtained were performed using high performance liquid chromatography. Total phenolic compounds, flavonoids, and radical scavenging capacity by 2, 2-azino-di-3-ethylbenzothi­alozine-sulphonic acid) assay were also determined. The highest content of steviol glycosides, total phenolic compounds, and fla­vonoids in stevia extracts were obtained when ultrasound assisted extraction was used. The antioxidant activity of the extracts was correlated with the total amount of phenolic compounds. The results indicated that the examined sonication parameters repre­sented as the probe diameter (7 and 22 mm) and treatment time (2, 4, 6, 8, and 10 min) significantly contributed to the yield of steviol glycosides, total phenolic compounds, and flavonoids. The optimum conditions for the maximum yield of steviol glycosides, total phenolic compounds, and flavonoids were as follows: extrac­tion time 10 min, probe diameter 22 mm, and temperature 81.2°C.
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