Antioxidant power quantification of decoction and cold infusions of Hibiscus sabdariffa flowers

In this paper the overall antioxidant power, expressed as Briggs-Rauscher antioxidant index, of decoction or cold infusions of dried Hibiscus sabdariffa flowers was determined at 25 and 37 degrees C, to compare the scavenger ability of the beverages at either room or physiological temperature. Total polyphenol contents and the absorbance of anthocyanin pigments were also determined, and the trend with the overall antioxidant capability is considered. Combined photometric and pH-metric titrations were acquired to obtain information on the colour-total acidity relationship of the product. The results show that the decoction preparation protocol provides karkade with the highest nutritional value and that the polyphenol content can account for the antioxidant capability of H. sabdariffa-based beverages. Moreover, a quantitative relationship between acid-base and redox chemistry was found. The H. sabdariffa-based drinks can be considered as protective beverages and a regular consumption of karkade might be proposed to ensure protection against free radicals. (c) 2005 Elsevier Ltd. All. rights reserved.