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Kefir – a complex probiotic Edward R. Farnworth Food Research and Development Centre, Agriculture and Agri-food Canada, St. Hyacinthe, Quebec, Canada J2S 8E3. Tel. 450-773-1105. Fax 450-8461. E-mail [email protected] Abstract Kefir is a fermented milk drink produced by the actions of bacteria and yeasts contained in kefir grains, and is reported to have a unique taste and unique properties. During fermentation, peptides and exopolysacchar- ides are formed that have been shown to have bioactive properties. Moreover, in vitro and animal trials have shown kefir and its constituents to have anticarcinogenic, antimutagenic, antiviral and antifungal properties. Although kefir has been produced and consumed in Eastern Europe for a long period of time, few clinical trials are found in the scientific literature to support the health claims attributed to kefir. The large number of microorganisms in kefir, the variety of possible bioactive compounds that could be formed during fermenta- tion, and the long list of reputed benefits of eating kefir make this fermented dairy product a complex probiotic. Keywords: kefir, probiotics, kefir grains, kefiran, human health, bioactive ingredients 1. Introduction Archaeological evidence has indicated that the process of fermentation in foods was discovered accidentally thou- sands of years ago. However, over time, it soon became apparent that many fermented foods had longer storage lives and improved nutritional values compared to their unfermented equivalents, making this form of food proces- sing a popular technique. It is not surprising, therefore, to find that many foods including vegetables, fruits, cereals, meat and fish have all been converted into desirable food products by fermentation and are still being consumed throughout the world today (Farnworth 2004). Certain bacteria, either alone or through the changes they bring about during fermentation, have been shown to have positive effects on health as well as resistance to dis- ease. Interest in such probiotic species has increased in recent years as more is learned about the microorganisms used in the fermentation process, and the possibility of adding beneficial bacteria to food products. Furthermore, consumers are increasingly looking to improve their health and increase their resistance to disease through dietary means. Fermented dairy products from milk from a variety of animals are perhaps the most common fermented foods worldwide. Yoghurt, which is known by many different names in different countries, is a fermented product which is familiar to consumers. Kefir, meanwhile, is less well known than yoghurt; however, an analysis of its composi- tion indicates that it may contain bioactive ingredients that give it unique health benefits, which means that kefir may be an important probiotic product (Farnworth 1999). 2. Origins of kefir Kefir is a viscous, slightly carbonated dairy beverage that contains small quantities of alcohol and, like yoghurt, is believed to have its origins in the Caucasian mountains of the former USSR. It is also manufactured under a variety of names including kephir, kiaphur, kefer, knapon, kepi and kippi (Koroleva 1988a), with artisanal production of kefir occurring in countries as widespread as Argentina, Taiwan, Portugal, Turkey and France (Thompson et al. 1990; Angulo et al. 1993; Lin et al. 1999; Garrote et al. 2001; Santos et al. 2003; Gulmez and Guven 2003). It is not clear whether all kefirs originate from a single original starter culture, since microbial analyses of kefir samples taken from different locations indicate microflora popula- tion differences. The FAO/WHO (2001) have proposed a definition of kefir based on the microbial composition of both kefir grains (the starter culture used to produce kefir) and the final kefir product (see Table 1). 3. Kefir manufacture Although commercial kefir is traditionally manufactured from cows’ milk, it has also been made from the milk of ewes, goats and buffalos. Moreover, kefir produced using soy milk has also been recently reported (Ismail et al. Food Science and Technology Bulletin: Functional Foods 2 (1) 1–17 DOI: 10.1616/1476-2137.13938. Published 4 April 2005 ISSN 1476-2137 # IFIS Publishing 2005. All Rights Reserved ......................................................................................................................................................................

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Ker a complex probioticEdward R. FarnworthFood Research and Development Centre, Agriculture and Agri-food Canada, St. Hyacinthe, Quebec, Canada J2S 8E3. Tel. 450-773-1105. Fax 450-8461. E-mail [email protected] AbstractKer is a fermented milk drink produced by the actions of bacteria and yeasts contained in ker grains, and is reported to have a unique taste and unique properties. During fermentation, peptides and exopolysaccharides are formed that have been shown to have bioactive properties. Moreover, in vitro and animal trials have shown ker and its constituents to have anticarcinogenic, antimutagenic, antiviral and antifungal properties. Although ker has been produced and consumed in Eastern Europe for a long period of time, few clinical trials are found in the scientic literature to support the health claims attributed to ker. The large number of microorganisms in ker, the variety of possible bioactive compounds that could be formed during fermentation, and the long list of reputed benets of eating ker make this fermented dairy product a complex probiotic. Keywords: ker, probiotics, ker grains, keran, human health, bioactive ingredients

1. IntroductionArchaeological evidence has indicated that the process of fermentation in foods was discovered accidentally thousands of years ago. However, over time, it soon became apparent that many fermented foods had longer storage lives and improved nutritional values compared to their unfermented equivalents, making this form of food processing a popular technique. It is not surprising, therefore, to nd that many foods including vegetables, fruits, cereals, meat and sh have all been converted into desirable food products by fermentation and are still being consumed throughout the world today (Farnworth 2004). Certain bacteria, either alone or through the changes they bring about during fermentation, have been shown to have positive effects on health as well as resistance to disease. Interest in such probiotic species has increased in recent years as more is learned about the microorganisms used in the fermentation process, and the possibility of adding benecial bacteria to food products. Furthermore, consumers are increasingly looking to improve their health and increase their resistance to disease through dietary means. Fermented dairy products from milk from a variety of animals are perhaps the most common fermented foods worldwide. Yoghurt, which is known by many different names in different countries, is a fermented product which is familiar to consumers. Ker, meanwhile, is less wellFood Science and Technology Bulletin: Functional Foods 2 (1) 117 DOI: 10.1616/1476-2137.13938. Published 4 April 2005 ISSN 1476-2137 # IFIS Publishing 2005. All Rights Reserved

known than yoghurt; however, an analysis of its composition indicates that it may contain bioactive ingredients that give it unique health benets, which means that ker may be an important probiotic product (Farnworth 1999).

2. Origins of kerKer is a viscous, slightly carbonated dairy beverage that contains small quantities of alcohol and, like yoghurt, is believed to have its origins in the Caucasian mountains of the former USSR. It is also manufactured under a variety of names including kephir, kiaphur, kefer, knapon, kepi and kippi (Koroleva 1988a), with artisanal production of ker occurring in countries as widespread as Argentina, Taiwan, Portugal, Turkey and France (Thompson et al. 1990; Angulo et al. 1993; Lin et al. 1999; Garrote et al. 2001; Santos et al. 2003; Gulmez and Guven 2003). It is not clear whether all kers originate from a single original starter culture, since microbial analyses of ker samples taken from different locations indicate microora population differences. The FAO/WHO (2001) have proposed a denition of ker based on the microbial composition of both ker grains (the starter culture used to produce ker) and the nal ker product (see Table 1).

3. Ker manufactureAlthough commercial ker is traditionally manufactured from cows milk, it has also been made from the milk of ewes, goats and buffalos. Moreover, ker produced using soy milk has also been recently reported (Ismail et al.

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Ker a complex probiotic E.R. Farnworth

Table 1. Codex Alimentarius description of ker*Denition Starter culture prepared from ker grains, Lactobacillus keri, and species of the genera Leuconostoc, Lactococcus and Acetobacter growing in a strong specic relationship. Ker grains constitute both lactose-fermenting yeasts (Kluyveromyces marxianus) and non-lactose-fermenting yeasts (Saccharomyces unisporus, Saccharomyces cerevisiae and Saccharomyces exiguus). Composition Milk protein (% w/w) Milk fat (% m/m) Titratable acidity, expressed as % of lactic acid (% m/m) Ethanol (% vol./w) Sum of specic microorganisms constituting the starter culture (cfu/g, in total) Yeasts (cfu /g) min. 2.8