Antioxidant and antimicrobial activities of tea infusions M. Pilar Almajano a , Rosa Carbo ´ a , J. Angel Lo ´pez Jime ´nez b , Michael H. Gordon c, * a Chemical Engineering Department, The Technical University of Catalonia, Av. Diagonal 649, 08034, Barcelona, Spain b Physiology Department, Faculty of Biology, University of Murcia, 30100 Murcia, Spain c Hugh Sinclair Unit of Human Nutrition, Department of Food Biosciences, University of Reading, Whiteknights, P.O. Box 226, Reading RG6 6AP, UK Received 15 February 2007; received in revised form 23 September 2007; accepted 11 October 2007 Abstract Tea polyphenols, especially the catechins, are potent antimicrobial and antioxidant agents, with positive effects on human health. White tea is one of the less studied teas but the flavour is more accepted than that of green tea in Europe. The concentrations of various catechins in 13 different kinds of infusion were determined by capillary electrophoresis. The total polyphenol content (Folin–Ciocalteu method), the trolox equivalent antioxidant capacity (TEAC value determined with the 2,2 0 -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation) and the inhibitory effects of infusions on the growth of some microorganisms were determined. Five different infu- sions (black, white, green and red teas and rooibos infusion) were added to a model food system, comprising a sunflower oil-in-water emulsion containing 0% or 0.2% bovine serum albumin (BSA), and the oxidative stability was studied during storage at 37 °C. Oxidation of the oil was monitored by determination of the peroxide value. The highest radical-scavenging activity observed was for the green and white teas. Emulsions containing these extracts from these teas were much more stable during storage when BSA was present than when it was not present, even though BSA itself did not provide an antioxidant effect (at 0.2% concentration). Rooibos infusion did not show the same synergy with BSA. Green tea and white tea showed similar inhibitions of several microorganisms and the magnitude of this was comparable to that of the commercial infusion 2 (C.I.2), ‘‘te ´ de la belleza”. This tea also had an antioxidant activity comparable to green tea. Ó 2007 Published by Elsevier Ltd. Keywords: Antioxidant activity; Antimicrobial; Bovine serum albumin; Emulsions; Polyphenols; Tea 1. Introduction 1.1. General The importance of diet for the prevention of some dis- eases is well recognized (Sur, Chandhuri, Vedasiromoni, Gomes, & Ganguly, 2001; Wongkham et al., 2001; Yao, Tan, Zhang, Su, & Wei, 1998) Antioxidant components are most important in foods because of their ability to reduce free radical-mediated degradation of cells and tis- sues in an organism (Jin, Hakamata, Takahashi, Kotani, & Kusu, 2004; Wongkham et al., 2001). Vegetables, legumes and whole-grain cereals (Karakaya & Kavas, 1999; Nihal, Ahmad, Mukhtar, & Wood, 2005) are good sources of antioxidants but there are many other food sources. Herbal infusions (specially tea) are also important sources (Marongiu et al., 2004; Wu, Ng, & Lin, 2004). The average estimated consumption of tea in the United King- dom is 1 l/person/day (Karakaya & Kavas, 1999; Yana- gimoto, Ochi, Lee, & Shibamoto, 2003). Black tea is the most popular drink in the West, and the consumption of green tea is less (18–20%). Less than 2% of tea consumed corresponds to oolong tea, which is very common in China and Taiwan (Karakaya & Kavas, 1999; Wheeler & Wheeler, 2004; Yao et al., 1998; Yen & Chen, 1995). Many investigators have studied tea properties, especially their health-related properties, including antimicrobial and 0308-8146/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.foodchem.2007.10.040 * Corresponding author. E-mail address: m.h.gordon@reading.ac.uk (M.H. Gordon). www.elsevier.com/locate/foodchem Available online at www.sciencedirect.com Food Chemistry 108 (2008) 55–63 Food Chemistry