Food Research International 33 (2000) 409±421 www.elsevier.com/locate/foodres Tea, Kombucha, and health: a review C. Dufresne, E. Farnworth * Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Blvd. West, Saint-Hyacinthe, QC, Canada J2S 8E3 Received 21 June 1999; accepted 1 December 1999 Abstract Kombucha is a refreshing beverage obtained by the fermentation of sugared tea with a symbiotic culture of acetic bacteria and fungi, consumed for its bene®cial eects on human health. Research conducted in Russia at the beginning of the century and tes- timony indicate that Kombucha can improve resistance against cancer, prevent cardiovascular diseases, promote digestive func- tions, stimulate the immune system, reduce in¯ammatory problems, and can have many other bene®ts. In this paper, we report on studies that shed more light on the properties of some constituents of Kombucha. The intensive research about the eects of tea on health provide a good starting point and are summarized to get a better understanding of the complex mechanisms that could be implicated in the physiological activity of both beverages. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Tea; Kombucha; Health; Chemical composition; Bene®cial property; Adverse reactions; Review 1. Introduction known medicine. It was taken in China 5000 years ago for its stimulating and detoxifying properties in the A large amount of information has been published elimination of alcohol and toxins, to improve blood and concerning the eects of tea and its major constituents urine ¯ow, to relieve joint pains, and to improve resis- on human health. This beverage has been consumed in tance to diseases (Balentine, Wiseman & Bouwens, many countries for a very long time, and today interest 1997). Tea grew rapidly in importance and was incor- is growing because scienti®c reports indicate that tea porated into many social rituals notably in China, could bring bene®ts for health and may help prevent Japan and England. Today, tea is the second most chronic diseases. Tea was ®rst introduced into Eur- popular beverage in the world after water (Yang & opean countries from China by Portuguese and Dutch Wang, 1993). explorers as a medicinal herb (Hollman, Hertog & Another beverage known as Kombucha, is produced Katan, 1996). Over the years, tea consumption became by the fermentation of tea and sugar by a symbiotic associated with eating and living habits just like coee association of bacteria and yeasts forming a ``tea fun- or soft drinks without regards to its bene®ts. The aging gus''. It also originated in China where the ``Divine of the population and limitations of modern medicine Che'' was prized 220 BC during the Tsin Dynasty for its have caused many people to look for new ways to detoxifying and energizing properties (Roche, 1998). In improve their health. Doubts surrounding lifestyle and 414, Doctor Kombu brought the tea fungus to Japan diet along with the growing interest in functional foods from Korea to cure the digestive troubles of the and nutraceuticals have contributed to this trend. Emperor. ``Tea Kvass'' was introduced into Russia by When we study the development of civilization and oriental merchants and then into Eastern Europe and the role of food and folk medicine, we often discover Europe around the turn of this century. This refreshing that many foods and beverages were used for their beverage tasting like sparkling apple cider is often pro- assumed bene®cial eects on health. Tea is the oldest duced in the home by fermentation using a tea fungus passed from home to home. The composition and properties of tea are well docum- * Corresponding author. Fax: +1-450-773-8461. ented, but scarce scienti®c information is available con- E-mail address: [email protected] (E. Farnworth). cerning the composition and the eects of Kombucha 0963-9969/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0963-9969(00)00067-3 410 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 on health. Bene®ts have been reported by testimony of Black tea and white sugar are the best substrates for users in dierent conditions and with variable con- the preparation of Kombucha, although green tea can summation. The purpose of this review is to point out be used also (Reiss, 1994). Tea leaves are added to the biological activity of both beverages, the speci®c boiling water and allowed to infuse for about 10 min substances implicated in the biological activity, and to after which the leaves are removed. Sucrose (50 g/l) is try to establish a better understanding of Kombucha dissolved in the hot tea and the preparation is left to and its possible health bene®ts. A thorough knowledge cool. Tea is poured into a wide-mouthed clean vessel of tea, its composition and eects on metabolism and and is acidi®ed by the addition of vinegar or already health provides a starting point to understanding the prepared Kombucha. The tea fungus is laid on the tea potential of Kombucha. surface, and the jar is carefully covered with a clean cloth and fastened properly. The preparation is allowed to incubate at room temperature (between 20 and 2. From tea to Kombucha: the fermentation process 30C) for 1±8 weeks. During fermentation, a daughter tea fungus is formed at the tea surface. The tea fungus is Tea plants belong to the Theaceae family and come removed from the surface and kept in a small volume of from two main varieties: Camellia sinensis var. sinensis fermented tea. The beverage is passed through cheese- and Camellia sinensis var. assamica (Hara, Luo, Wick- cloth and stored in capped bottles at 4C. The taste of remashinghe & Yamanishi, 1995a). The ®rst apical the Kombucha changes during fermentation from a leaves are picked from the evergreen shrub and can be pleasant fruit sour-like lightly sparkling ¯avour after a processed by dierent methods. Green tea is readily few days, to a mild vinegar-like taste with prolonged dried with or without a ®xation step to inactivate incubation (Blanc, 1996; Reiss, 1994; Sievers, Lanini, enzymes (Hara, Luo, Wickremashinghe & Yamanishi, Weber, Schuler-Schmid & Teuber, 1995). 1995b). Black tea, the most popular form around the The microbiological composition of the tea fungus world, is the result of the oxidation of leaf polyphenols has been investigated. Bacteria and fungus present in through a multi-stage enzymatic process (Hara, Luo, Kombucha form a powerful symbiosis able to inhibit Wickremashinghe & Yamanishi, 1995d). New poly- the growth of potential contaminating bacteria (Balen- phenol molecule complexes are formed during the pro- tine, 1997; Liu, Hsu, Lee & Liao, 1996). The main acetic cessing of black tea (Fig. 1) acid bacteria found in the tea fungus are: Acetobacter xylinum (Balentine, 1997), A. xylinoides, Bacterium glu- conicum (Reiss, 1994), A. aceti, A. pasteurianus (Liu et al., 1996). Yeasts identi®ed as Schizosaccharomyces pombe, Saccharomycodes ludwigii, Kloeckera apiculata, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Brettanomyces bruxellensis, B. lambicus, B. custersii, Candida and Pichia species (Balentine, 1997; Liu et al., 1996; Mayser, Fromme, Leitzmann & GruÈ nder, 1995) have been isolated from tea fungus. Aspects of the close association between micro-organisms that make up the fungus and their interaction with the substrates sup- porting fermentation have been studied (Balentine, 1997; Sievers et al., 1995; Yurkevich & Kutyshenko, 1998). Acetobacter xylinum has the ability to synthesize a ¯oating cellulose network which enhances the association formed between bacteria and fungi (Balentine et al., 1997). The yeast cells convert sucrose into fructose and glucose and produce ethanol (Reiss, 1994; Sievers et al., 1995). Acetic acid bacteria convert glucose to gluconic acid and fructose into acetic acid. Caeine and related xanthines of the tea infusion stimulate the cellulose synthesis by the bacteria, (Balentine et al., 1997). Acetic acid stimulates the yeast to produce ethanol and ethanol in turn can be helpful to acetic acid bacteria to grow and produce acetic acid (Liu et al., 1996). Both ethanol and acetic acid have been reported to have antimicrobial activity against pathogenic bacteria thereby providing protection against contamination of Fig. 1. Chemical structure of some tea constituents. the tea fungus (Liu et al., 1996). C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 411 3. Tea and its biological activity animals, and in vitro studies lead to the conclusion that tea has potentially protective eects for a wide variety 3.1. Chemical composition of health conditions. However, the evidence is not always clear cut. The chemical composition of tea leaves has been thoroughly studied. The main constituents of green 3.2.1. Epidemiologic studies tea leaves belong to the polyphenol group accounting Epidemiologic studies have investigated the role of for 25±35% on a dry weight basis (Balentine et al., 1997; green tea (Bushman, 1998; Imai, Suga & Nakachi, Hara, Luo, Wickremashinghe & Yamanishi, 1995c). 1997), black tea (Blot, McLaughlin & Chow, 1997) or Important and characteristic tea polyphenols are both in cancer prevention often without conclusive the ¯avanols of which catechins (¯avan-3-ols) are pre- results (Yang & Wang, 1993; Yokozawa, Dong, Naka- dominant and the major ones are: ()-epicatechin (EC), gawa, Takeuchi et al., 1998). To make sense of data ()-epicatechin gallate (ECG), ()-epigallocatechin generated by epidemiologic