Food Technology
Reza Farahmandfar; Sahar Aboutalebzadeh; Hannaneh Moniri; Massoud Kaykhaii
Abstract
Black tea, which is obtained from the leaves of small tree Camellia sinensis, is a popular drink that has been consumed for centuries all around the world. In this study, a sample of Iranian black tea was brewed by two methods of microwave and traditional brewing and their extracts were then assessed ...
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Black tea, which is obtained from the leaves of small tree Camellia sinensis, is a popular drink that has been consumed for centuries all around the world. In this study, a sample of Iranian black tea was brewed by two methods of microwave and traditional brewing and their extracts were then assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays to determine their phenolic and flavonoid contents as well as heavy metal (HM) (copper, nickel, chromium, cadmium and lead) content. It was observed that there is a direct relationship between the antioxidant activity with their phenolic and flavonoid contents. The highest and lowest antioxidant activities were observed for samples brewed by microwave at 360 W for 2.5 min and 900 W for 7.5 min, respectively. As the brewing power and time increased, the antioxidant activity decreased. Brewing tea by microwave and traditional methods caused a significant reduction in the amount of heavy metals, which was lower than the allowable limit according to the Iranian national standards. These results demonstrate the importance of exposure time and radiation power when tea is prepared by microwave.
Reza Nassiri Rad; Mohammad Hossein Hadad Khodaparast; Amir Hossein Elhami Rad; Shiva Roufigari Haghighat
Abstract
Green Tea is prepared from the leaves of Camellia sinensis. Catechins of Green tea are well known as natural antioxidants and have effective beneficial on the body. One of the most important processes in the extraction of catechins and producing green tea beverage is brewing process. The object of this ...
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Green Tea is prepared from the leaves of Camellia sinensis. Catechins of Green tea are well known as natural antioxidants and have effective beneficial on the body. One of the most important processes in the extraction of catechins and producing green tea beverage is brewing process. The object of this study is to investigating the effect of brewing temperatures (60٫70 and 80˚c) and duration (5٫10 and 15 min) also the season effect of plucking on green tea that was produced in the Tea Research foundation of lahijan. results of total phenolic content on brewed green tea, is showed that plucking in summer and spring seasons samples have much total phenolic content are rather than plucking in autumn season samples also percent extraction of brewing green tea at 15 minuets has most highest total phenolic content than other seasons and brewing times .brewing temperature are not significant effected on the total phenolic content.
