Original article Thermal kinetic degradation of anthocyanins in a roselle (Hibiscus sabdariffa L. cv. ‘Criollo’) infusion Domı´nguez-Lo ´ pez Aurelio, 1 * Remondetto Gabriel Edgardo 2 & Salvador Navarro-Galindo 3 1 Facultad de Ciencias Agrı´colas, Universidad Auto´ noma del Estado de Me´xico, Campus Universitario ‘‘El Cerrillo’’ A. P. 435, Toluca, Estado de Me´xico, C. P. 50200, Mexico 2 Agropur Coope´rative, Division Fromages et Produits fonctionnels, 510, rue Principale Granby, Que´bec, Canada J2G 7G2 3 Campo Experimental Chilpancingo, Delegacio´n Estatal SAGARPA, Guerrero, Av. Ruffo Figueroa s/n, Col. Buro´cratas, Chilpancingo, Gro, Mexico (Received 4 May 2006; Accepted in revised form 6 September 2006) Summary The degradation kinetics of anthocyanins in a Roselle infusion (Hibiscus sabdariffa L.), as assessed by visible absorption spectroscopy (absorbance at 520 nm), was verified (60–100 °C). The rate constants for absorbance retention were obtained from first-order reaction kinetic plots. Based on an Arrhenius-type model, the experimental data showed an energy of activation of 15.83 kcal mol )1 (66.22 kJ mol )1 ) and a Q 10 value of 1.01. The obtained pattern allows to predict the retention of these antioxidant compounds as a function of temperature and time of thermal treatment. Keywords Anthocyanins, antioxidant properties, beverages, degradation kinetics, Hibiscus sabdariffa L., Karkade´, kinetics, roselle, thermal stability, visible absorption spectroscopy. Introduction Roselle also called Karkade´ or Jamaica flower (Hibiscus sabdariffa L.), is an annual shrub (family: Malvaceae) that grows in regions where dry tropical weather prevails; countries like Sudan, Thailand, China, Mexico, Egypt, Senegal and Tanzania with this type of natural environment are among the main producers of this plant. Cultivating roselle has diverse purposes in the world. In some countries, its shrubbery is used for decorative purposes; in others, seeds and petals are used for human consumption. Nevertheless, in most cases, it is cultivated with the purpose of using the calyx of their flowers to produce infusions that are consumed like tea. A roselle infusion, commonly mixed with some sweet- ener, is an intense red transparent liquid that shows a very low pH and an astringent flavour. In accordance with Wong et al. (2002) and Nnam & Onyeke (2003), the dehydrated roselle calyx are rich in organic acids (2.42 g of malic acid/100 g of fresh calyx), b-carotene (1.88 mg/100 g), Iron (833 mg/100 g), and ascorbic acid (141.1 g/100 g). However, its importance resides mainly in its anthocyanin content (2.52 g/100 g, according to Wong et al., 2002). An infusion of the red calyx cultivars of this plant contain mainly two antho- cyanins: delphinidin-3-xylosylglucoside and cyanidin-3- xylosylglucoside (Fig. 1) and in a small quantity the glucosides of these two molecules: delphinidin-3-glucos- ide and cyanidin-3 glucoside (Du & Francis, 1973). To date, the antioxidant properties of the anthocya- nins and anthocyanidins have been extensively evalu- ated. Ka¨hko¨nen & Heinonen (2003) found that the six anthocyanidins common in vegetables (pelargonidin, cyanidin, delphinidin, peonidin, petunidin and malvidin) and their derived glucosides produce a strong in vitro antioxidant activity. Robards et al. (1999) reported the effect of the phenolic compounds including anthocya- nins on the antioxidant properties of diverse fruits. These properties have been evaluated in roselle infusions by several groups of researchers (Duh & Yen, 1997; Tee et al., 2002; Tsai et al., 2002; Chen et al., 2004; Pale et al., 2004; Prenesti et al., 2007). The high-antioxidant properties of roselle infusions suggest that the daily consumption of these drinks can be beneficial to the human health. In fact, based on animal models (mainly rodents), it has been suggested that an infusion from the dried calyx of roselle can be used to inhibit the oxidation of low-density lipoproteins and to prevent various types of hyperlipidaemia (Chen et al., 2004; Hirunpanich et al., 2006). It also exhibits antihypertensive and cardio-protective effects (Odigie *Correspondent: Fax: +52-722-296-5518; e-mail: adl@uaemex.mx International Journal of Food Science and Technology 2008, 43, 322–325 322 doi:10.1111/j.1365-2621.2006.01439.x Ó 2007 The Authors. Journal compilation Ó 2007 Institute of Food Science and Technology Trust Fund