Kombucha as a Functional Beverage

KOMBUCHA AS A FUNCTIONAL BEVERAGE

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R. Jayabalan⁎, Viduranga Y. Waisundara† ⁎

Food Microbiology and Bioprocess Laboratory, Department of Life Science, National Institute of Technology, Rourkela, India, †Australian College of Business & Technology—Kandy Campus, Kandy, Sri Lanka

12.1  Introduction to Functional Foods and Beverages During the last two decades of the 20th century, there has been a tremendous rise in the understanding of the role of food in human health promotion. Various studies have given conclusions that food does not have only the role of being an energy source and contribute body building components, but also provide several bioactive components, which confer benefits to human health. By focusing on the bioactive constituents available in food products, a new category of food has been introduced which is called functional foods (Cencic and Chingwaru, 2010). In 1984, Japanese scientists explored the interactions among diet, fortification, sensory satisfaction, and inflection of physiological systems (Bigliardi and Galati, 2013), hence the coining of the term “functional food.” Subsequently, Japan launched >1700 functional foods during 1988 and 1998. Foods that improve the human health over and above the provision of basic nutrition are generally considered as functional foods. Japan has legally approved functional foods, regarding them as foods for specific health use (FOSHU), which however is not universally accepted (Stanton et al., 2005). Several organizations and researchers have proposed the definition for the functional foods in different ways which are given in the following: i. Foods that are same in appearance to a conventional food consumed as part of the usual diet, with established physiological benefits, and/or to reduce the risk of chronic disease beyond basic nutritional roles (Health Canada, 1998a,b). ii. Foods or ingredients of foods that provide an additional physiological benefit beyond their basic nutrition (International Life Sciences Institute, 1999). Functional and Medicinal Beverages. https://doi.org/10.1016/B978-0-12-816397-9.00012-1 © 2019 Elsevier Inc. All rights reserved.

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iii. Any modified food or food ingredients that may provide health benefits beyond that conferred by the traditional nutrients the food contains (Marriott, 2000). iv. Foods that can be reasonably proved to affect positively one or more target functions in the body, beyond adequate nutritional effects, in a way applicable to an improved state of health and well-being and/or lessening of risk of disease (Contor, 2001). Fruits and vegetables are considered the simplest form of functional foods as they are rich in antioxidant compounds such as polyphenols and carotenoids. Functional foods are always confused with nutraceuticals although they are related, but different in terms of concepts. Functional foods are foods consumed as part of everyday life, and they should be composed of natural components possibly available in unnatural concentrations or present in foods which would not normally supply them and must exert positive effects on target function(s) beyond their nutritive value and enhancing the well-being and quality of life, and/or decreasing the disease risk (El Sohaimy, 2012). In contrast, nutraceuticals are defined as a food (or part of food) that provides medical or health benefits, including the prevention and treatment of a disease. The term “nutraceutical” was first proposed in 1989 by Stephen DeFelice from the words “nutrition” and “pharmaceutical” (Brower, 1998). A nutraceutical is defined as a “product isolated or purified from foods that are sold in medicinal forms or associated with food, which provides medical or health benefits, including the prevention and/or treatment of chronic diseases” (HC, 1998b). Nutraceuticals differ from dietary supplements in the following aspects (Trottier et al., 2010): i. Nutraceuticals supplement dietary effect and help in the prevention and/or treatment of disease and/or disorder. ii. Nutraceuticals are used as conventional foods or as sole items of a meal or diet. The two concepts are different in their functions in which functional foods are mainly related to, especially in the aspect of reducing the risk of disease rather than preventing it, while nutraceuticals are consumed to promote well-being, through the prevention and/or treatment of diseases and/or disorders (Ghosh et al., 2014). The differences between functional food, nutraceuticals, and food supplements are provided in Table 12.1. The benefits of consuming functional food are provided in Table 12.2. Functional foods are being introduced in almost all food categories to fulfill the changing consumer preferences. Among the food categories, dairy, bakery, soft-drinks, confectionery, and baby-food categories are recorded as having more functional foods. Different classifications of functional foods exist. Sloan (2012), Kotilainen et al. (2006), and Spence (2006) have proposed the following product-based functional food classification:

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Table 12.1  General Similarities and Differences Between Functional Foods, Nutraceuticals, and Food Supplements Functional Foods

Nutraceuticals

Food Supplement

Definition

Foods or constituents of foods that provide an added physiological value beyond their basic nutrition

Have a feed function essentially, taking the form of medicines (pills or capsules)

Usual form of consumption

Consumed as conventional foods as per regular food pattern. Not consumed as pills or capsules and do not have any form of food supplement Daily as part of the diet

A product isolated or purified from foods that are sold in medicinal forms or related with food, which delivers medical or health benefits, including the prevention and/or treatment of chronic diseases Consumed as pills, tablets, capsules, syrup

Regular for a period when they are food constituents/extracts Exert pharmacological function and should not be confused with medicines which are administered in precise dose under medical supervision to treat or prevent a specific disease Food extract, single natural compound or nutrient and not necessarily a complete food (e.g., resveratrol, curcumin, vitamin E) which may be included in pharmaceutical form (pills, tablets, etc.) as dietary supplements and as part of a specific diet Promote beneficial effects through the prevention and/or treatment of diseases and/or disorders

Specific period

Frequency of consumption Pharmacological effect

Usually consumed on prophylaxis basis rather than therapeutic basis

Form of occurrence

Fortified foods with bioactive ingredients like vitamins, minerals, polyphenols, carotenoids, flavonoids, probiotics, prebiotics, etc.

Benefits

Positive health or physiological effect; improvement in state of health and well-being, and/or decreasing the disease risk

References

International Life Sciences Institute (1999), EU (2010), and International Food Information Council (2006)

Gupta et al. (2010), Sikora et al. (2010), and Silk and Smoliga (2014)

Not consumed as traditional food in the daily diet. Consumed as pills, tablets, capsules, syrup

Not considered as treating or preventing diseases

Concentrated form of the extracted ingredient packed as capsule or made into tablets

Ensuring the intake of certain ingredient(s), e.g., minerals, vitamins, amino acids, etc. May also help to reduce the risk of disease Howlett (2008)

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Table 12.2  Functional Foods and Their Potential Health Benefits (Abdel-Salam, 2010; Aluko, 2012) Functional Food

Potential Health Benefits

Whole foods Black and green tea

Decreases cancer risk, reduce development and severity of Alzheimer’s disease, Prevention of hypertension, cardiovascular damage, and endothelial dysfunction, beneficial effect on glucose metabolism, decrease bone mineralization Decrease cancer risk Decrease risk for heart related disease, diminishes cholesterol, and triglycerides Lessens risk of certain cancers and heart disease, decreases hypertension Decreases risk of heart disease and certain cancers, lessens cholesterol Decreases risk of cancers, and heart disease, controls blood glucose, reduces triglycerides Hypotensive effect and cholesterol-lowering effect

Broccoli Fish Fruits and vegetables Garlic Flaxseed Buckwheat Enriched foods with fibers Grains Fortified foods Juices with calcium Grains with folic acid Infant formulas with iron Grains with added fiber

Decreases risk of certain cancers, nutrient deficiencies, and heart disease Reduces risk of osteoporosis and hypertension Reduces problems related to heart and neural tube congenital disabilities Reduces risk of anemia Reduces cancer risk and heart-related problems, lowers cholesterol and constipation, and controls blood glucose Reduces osteomalacia and osteoporosis risk Decreases cancers risk and heart-related disease, reduces cholesterol, hypertension, and constipation

Milk with vitamin D Juices with added fiber Enhanced foods Dairy products with probiotics Fish oil with omega-3 fatty acids

Lessens colon cancer and candida vaginitis risks, controls inflammation, treats respiratory allergies, diarrheal disorders, and eczema Reduces risk of heart-related disease

i. Labeled fortified products: foods fortified with additional nutrients (e.g., fruit juices with zinc, calcium, folic acid, vitamin C and vitamin E). ii. Labeled enriched products: food with other novel nutrients or constituents not typically present in a particular food (e.g., probiotics or prebiotics). iii. Labeled altered products: food from which a harmful part has been removed, decreased or substituted by another with positive effects (e.g., fibers as fat releases in meat or ice cream).

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iv. Labeled enhanced commodities: food in which one of the constituents has been naturally enriched (e.g., eggs with increased omega-3 content). Based on the aim of the functional foods, the following classification has been carried out by Makinen-Aakula (2006): i. Functional foods that add good to life or progress children’s life, such as prebiotics and probiotics ii. Functional foods that diminish a prevailing health risk problem such as high cholesterol or high blood pressure iii. Functional foods which make life easier, such as lactose-free or gluten-free products Recently, probiotics were found to be the dominant functional food of both Japanese and European consumer markets. Lactic acid ­bacteria (LAB) and bifidobacteria are the most studied and widely used probiotics (Ouwehand, 2007). According to Makinen-Aakula (2006), Croatia, Estonia, Scandinavia, Switzerland, and the Netherlands followed by Greece, France, and Spain are the leading and emerging markets of probiotics.

12.1.1 Bioactive Ingredients and Their Sources The functional molecule of a functional food is the biologically a­ ctive ingredient present in it. They may be present in very less concentration from microgram to milligrams, but they exert different benefits to the human body. They are basically bioactive phytochemicals like carotenoids (β-carotene, lutein, zeaxanthin, lycopene, etc.), polyphenols, and flavonoids (quercetin, epigallocatechin, kaempferol) present in whole fruits and vegetables, bioactive peptides (fermented bovine and soy milk products), bioactive fatty acids (monounsaturated and polyunsaturated fatty acids like omega 3 and 6 fatty acids) present in fish and fish products, dietary fibers (insoluble and soluble fibers like β-glucan) present in whole fruits and mushrooms, vitamins and minerals (fruits, vegetables, cereals, and pulses), and others. A list of bioactive ingredients with their sources and beneficial effects are given in Table 12.3. Although the bioactive components are present in decidedly fewer concentrations in foods, it is sufficient to exert the biological activities if they are absorbed in the right amount. Bioavailability of the bioactive ingredients is essential; else the ingredient will fail to show their beneficial effects on the host. Secoisolariciresinol diglucosdie (SDG) is reported to have an anticancer effect, but its bioavailability is very poor in the ranges of a few nanomoles to a few micromoles per liter of human plasma or urine. SDG’s anticancer effect is believed to be mediated through the production of its metabolites, enterolactone, and enterodiol via anaerobic fermentation by colon bacteria (Ayella et al., 2010). Bioavailability of tea catechins is also low due to

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Table 12.3  Bioactive Ingredients Present in Functional Foods and Their Beneficial Effects Food

Bioactive Ingredient

Beneficial Effects

Reference

Soybean

Proteins, estradiol (estrogen), genistein and daidzein (isoflavone)

Aukema et al. (2011) and Yang et al. (2011)

Fruits and vegetables

Polyphenol—ellagic acid, vitamin C, anthocyanins, (strawberry, raspberry, black currants, grapes), vitamin C, proanthocyanidins, hydroxycinnamic acids, folic acid, manganese, dietary fiber Casein and whey proteins (lactalbumins and lactoglobulins), minor proteins and peptides, lysozyme, transferrin, lactoferrin, hormones (insulin, somatostatin, adrenocorticotropin, prolactin, etc.), lactoperoxidase, enzymes, colostrum, immunoglobulins, oligosaccharides, gangliosides, N-acetylneuraminic acidcontaining components, mucin, epithelial growth factors, insulin-like growth factors, transforming growth factors, vascular endothelial growth factors, plateletderived growth factors Fish oil, proteins, minerals (copper, calcium, selenium, zinc, and magnesium), vitamin B1

Cholesterol-lowering effects, beneficial effect on cardiovascular disease, renal disease, cancer, bone health, menopause, nonalcoholic fatty liver disease Beneficial effects on cancer, cardiovascular health, inflammation, diabetes

Anticarcinogen, antimicrobial, strengthening immune system, beneficial effect on gastrointestinal tract

Ramachandran and Shah (2011) and Kuhara et al. (2012)

Beneficial effects on cardiovascular diseases, brain function, cancer, immune system, obesity, kidney disease, digestive tract system Beneficial effects on cancer, diabetes, kidney disease, hypertension

Peake et al. (2011) and Tsuduki et al. (2011)

Beneficial effects on cardiovascular diseases, hypercholesterol Beneficial effects on hypercholesterol, diabetes

Ros (2010)

Milk and milk products

Fish

Whole-grain cereals

Amaranth seeds Barley

Digestible carbohydrates, dietary fiber, proteins, vitamins (B group and vitamin E), minerals (zinc, phosphorous, selenium, and iron), phenolic compounds, phytoestrogens, antioxidants Dietary fiber, polyphenols (anthocyanins and flavonoids) Dietary fibers (beta-glucan, arabinoxylans, and cellulose)

Mari Kannan and Darlin Quine (2012) and Patel et al. (2011)

Flight and Clifton (2006)

Dongowski et al. (2002)

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Table 12.3  Bioactive Ingredients Present in Functional Foods and Their Beneficial Effects—cont’d Food

Bioactive Ingredient

Beneficial Effects

Reference

Wheat and triticale

Dietary fibers (arabinoxylans and hemicelluloses)

Adam et al. (2001)

Whole-grain flaxseed Buckwheat

Bioactive fatty acids and lignans (secoisolariciresinol diglucosdie, SDG) Proteins and flavonoids, 2′-hydroxynicotinamine (HNA), D-chiroinositol (D-CI) Epigallocatechin (ECG), and epigallocatechin gallate (EGCG), theanine

Beneficial effects on hypercholesterol, removal of toxins and carcinogens Inhibition of tumor development Beneficial effects on chronic diseases, cholesterol-lowering effect, antihyperglycemic effect Antimicrobial, antioxidant, anti-inflammatory, anticancer, increasing innate immune functions, reduce the development of Alzheimer’s disease, prevention of hypertension, cardiovascular damage and endothelial dysfunction, beneficial effect on obesity, hepatic injury, and osteoporosis, protective effects against tumor initiation, promotion, and progression Stimulatory effects on brain, protection against chronic diseases, diabetes, Parkinson’s, and Alzheimer’s disease

Kawa et al. (2003)

Tea (green and black)

Coffee

Caffeine, caffeic acid, chlorogenic acid, hydroxyhydroquinone

Plant nuts

Lipids with high contents of unsaturated fatty acids, high fiber, high protein contents, folic acid, Mg, Cu, flavonoids, phenolic compounds, isoflavones, sterols, etc. Polysaccharides with alpha-1,4; beta-1,3; beta-1,6; and beta-1,2 Nondigested oligosaccharides, fructose, vitamins, minerals, antioxidants Flavanols

Mushrooms Honey Cocoa and chocolate products

Improving cardiovascular functions, reducing visceral adiposity, improving insulin sensitivity

Ayella et al. (2010)

Antonello et al. (2007), Chen et al. (2011), and Harvey et al. (2011)

Butt and Sultan (2011), De Marco et al. (2011), and Matsudo et al. (2011) Ros (2010) and Relja et al. (2012)

Antitumor properties Regulation of body weight reduced hypertriglyceridemic effect Increase vascular relaxation, potential cardiovascular health benefits

Nemoseck et al. (2011) Grassi et al. (2010)

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their short in vivo half-life (maximum of about 5 h); hence, it is necessary to take a repeated dose in a day to keep the high concentration of plasma levels (Chen et al., 2011; Harvey et al., 2011).

12.1.2  Functional Beverages The functional beverage sector is the fastest growing segment of the beverage industry. The consumption of functional beverages was 250 L per year per capita in 2006. However, the use of carbonated soft drinks during 2006–09 fell from 730 L to 190 per year per capita. These numbers illustrate the trend toward the healthier beverage choice among the US population. The same pattern is observed in other developed and developing nations. Functional beverages are becoming famous for the following reasons: i. easy for a person to choose to drink a healthier beverage than a food, ii. beverages are a better vehicle for the consumption of healthy ­supplement-like additives than foods. Functional beverages are divided into four types. They are: i. Hydration beverages contain defined concentrations of salts and minerals. Different vitamins and minerals are added to attract the consumers. ii. Energy or rejuvenation beverages contain stimulants like caffeine, guarana, taurine, and yerba matte. Fortification of energy drinks with B vitamins, ginseng, ginko biloba, creatine, and flavonoids is also becoming popular. iii. Health and wellness beverages are developed for the people concerned about their general health and wellness. Low-calorie beverages made with stevia (a natural low-calorie sweetener) and added with various vitamin combinations are becoming very popular. iv. Weight management beverages target the obese consumer due to their weight loss claims. These beverages are added to polyphenols, green tea, and green coffee extracts and are labeled with claims that they promote weight loss by increasing metabolism.

12.2  Introduction to Kombucha Tea Kombucha tea is a fermented beverage which has gained popularity recently due to its purported health benefits. As somewhat of a value-added form of tea—for which functional properties have already been established, the beverage itself has a history spanning several thousands of years in the East, while it soon became popular in the West as well owing to the comparatively acceptable taste, flavor, and ease of preparation (Mohammadshirazi and Kalhor, 2016). While the term “Kombucha” is the most commonly used name for

Chapter 12  Kombucha as a Functional Beverage   421

the beverage, it is also known by other names such as Chainii grib, Chainii kvass Champignon de longue vie, Ling zhi, kocha kinoko, and red tea fungus (Malbaša et al., 2011). Kombucha is produced by the fermentation of tea and sugar by a symbiotic association of bacteria and yeasts collectively forming a “tea fungus”—a name owing to the mushroom-like growth appearing in the fermented broth. Typically, black or green tea can be used as the medium of fermentation and the period of incubation may vary from a few days up to 2 weeks. Similar to green tea and black tea, kombucha tea can also be bottled for commercialization once the fermentation process is complete (Jayabalan et al., 2008). The fermented product is a slightly sweet and carbonated acidic beverage resulting from numerous compounds which are produced by the symbiotic metabolic activities of the bacterial and yeast culture (Fig. 12.1). While many bioactive compounds are produced as a result of the fermentation, the process also leads to the formation of cellulose pellicles due to the activity of some bacterial strains such as Gluconacetobacter xylinum (Johnsy et al., 2005; Kallel et al., 2012; Mohammadshirazi and Kalhor, 2016). The beverage possesses a similar flavor as apple cider, although it can be comparatively more acidic and alcoholic (Watawana et al., 2015a,b,c). The biofilm which is used to carry out the kombucha fermentations is directly produced by indigenous microorganisms existing in the sweetened tea, making the process quite similar to traditional vinegar production (Coton et al., 2017). Each fermentation leads to a new biofilm layer which appears in the shape and form of a mushroom, and can be used for future fermentations as a starter culture. The mushroom-like appearance was once the reason it was given the

Fig. 12.1  Kombucha prepared using black tea after 7 days of fermentation. The disc-shaped tea fungal mat is shown amidst the fermented broth.

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scientific name of Medusomyces gisevii by Lindau in 1965 (Jayabalan et al., 2014). Although the fermented broth is typically consumed in the form of a beverage, it can also be used for topical purposes. Variations in both chemical and microbial composition of the beverage can be observed owing to differences in tea varieties (black, green, and geographical origin), microbial culture conditions, process technologies, and duration of fermentation (Coton et  al., 2017; Mukadam et al., 2014). These variations also result in different types of compounds present in the fermented broth, thus, producing beverages of diverse functional properties. When it comes to the microbial composition of the tea fungal mat, species of Gluconacetobacter, including Gluconacetobacter xylinum as a characteristic species, and various yeasts, such as the genera of Brettanomyces, Zygosaccharomyces, Saccharomyces, and Pichia have been identified depending on the source (Chu and Chen, 2006). The most important of these species are those which produce bacterial cellulose, such as Komagataeibacter xylinus, which was recently reclassified from Gluconacetobacter xylinus (also previously known as Acetobacter xylinum) (Marsh et  al., 2014; Yamada et al., 2012). Under aerobic conditions, kombucha symbiosis is capable of converting a very simple substrate (sucrose and black or green tea), over a period of 7–10 days, into a slightly carbonated, mildly sour, and refreshing beverage. The methodology of preparing the beverage is shown in Fig. 12.2. This beverage is composed of sugars, ­gluconic, glucuronic, l-lactic, acetic, malic, tartaric, malonic,

Fig. 12.2  Typical preparation steps of kombucha. Exact quantities of ingredients may vary.

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citric, and oxalic acids, as well as ethanol, amino acids, ­water-soluble vitamins, antibiotically active matters, and some hydrolytic enzymes (Balentine et  al., 1997; Bauer-Petrovska and Petrushevska-Tozi, 2000; Chen and Liu, 2000; Hesseltine, 1965; Kappel and Anken, 1993; Malbaša et al., 2011; Pasha and Reddy, 2005). Most importantly, the acids produced during fermentation shield the symbiotic colony present in the tea fungal pellicle from contamination with unwanted foreign microorganisms which are essentially not part of the tea fungus (Sreeramulu et al., 2000). It has to be borne in mind though that majority of microbiology-­ orientated studies of kombucha to date have been culture based (Marsh et al., 2014). These are limited in that certain species can be difficult to isolate and the exclusive reliance on phenotypic traits can easily lead to misidentification (Raspor and Goranovic, 2008). However, the recent study by Marsh et al. (2014) which engaged the high-throughput amplicon sequencing performed on DNA extracts from cellulosic pellicles sourced from five distinct geographic locations, provided the most indepth analysis of the kombucha microflora to date. Marsh et al. (2014) reported that Zygosaccharomyces, Dekkera, and Kazachstania were the only genera detected across the various fermented tea samples, while several other genera were detected in the pellicle samples and were represented by only one species. Of these, Davidiella tassiana, Lachancea fermentati, Kluyveromyces marxianus, Naumovozyma castellii, and the Basidiomycota representatives, Wallemia sebi, and Leucosporidiella fragaria were not previously reported to have been found in kombucha. On the other hand, in comparison to the study by Marsh et al. (2014), the study by Chakravorty et al. (2016) indicated that a culture-dependent analysis might not be sufficient to describe the overall microbial community structure and to also depict the rare microbes of the systems. Nevertheless, the study by Marsh et al. (2014) concluded that a naturally low pH and ethanol content of the beverage which is generated under regular household brewing conditions, combined with other forms of competition involving the indigenous microbial population, is sufficient to limit contamination from undesirable populations. The type of sweetening agent used for the preparation of the tea which is subjected to the tea fungus also plays a role in the formulation of the final product. Rodrigues et al. (2006) for instance had used molasses from sugar beet for the fermentation process. However, many other low-cost sweeteners exist which are mostly used for indigenous culinary applications. Watawana et al. (2017) used the following sweetening agents for the preparation of Kombucha beverages: artificial sweetener—aspartame, bees’ honey, brown sugar, white sugar, glucose, kitul palm honey (Caryota urens), palmyrah jaggery (Borassus flabellifer), and sucrose—which was the control. The f­luctuations in

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the antioxidant and starch hydrolase inhibitory activities were observed in this study during a fermentation period of 7 days. Brown sugar, white sugar, glucose, and sucrose were the most effective in producing high antioxidant and starch hydrolase inhibitory activities in this study, while usage of bees’ honey, C. urens honey, and palmyrah jaggery had not necessarily deterred the fermentation.

12.3  Kombucha Tea as a Functional Beverage The US Food and Drug Administration and Kappa Laboratories, Miami, Florida, have carried out microbiological and biochemical tests and reported that Kombucha is safe for human consumption (Vina et al., 2014). There have been numerous health-promoting virtues reported about kombucha and due to the straightforward and safe preparation, this beverage has gained widespread popularity among consumers all around the world. It has been proven experimentally that kombucha broth has the four main potencies necessary for numerous biological activities: A detoxifying property, protection against free-radical damage, energizing capabilities, and promotion of immunity (Vina et al., 2014). Primarily, the beverage has been intensively consumed worldwide for a very long time, owing to its prophylactic and therapeutic properties (Battikh et  al., 2013; Durfesne and Farnworth, 2000; Morshedi and Dashti-Rahmatabadi, 2010; Yang et al., 2009). Systematic investigations of the antimicrobial activity of kombucha by Sreeramulu et al. (2001), the antimicrobial compounds other than organic acids or proteins (enzymes) produced during fermentation as well as tannins are originally present in the tea broth. In the study by Battikh et  al. (2013), kombucha exhibited its strongest antimicrobial effect against Staphylococcus epidermidis, Micrococcus luteus, Listeria monocytogenes, and Pseudomonas aeruginosa. The study investigated variations in the antimicrobial effects between green and black tea-based kombucha beverages. It was demonstrated that the behavior of the same strain was different in terms of the green fermented tea, where the activity was improved by tea acidification and such activity remained constant after heat treatment (Battikh et  al., 2013). This finding means that the antibacterial activity observed is not exclusively due to acetic acid or other organic acids; other components that are biologically active, such as bacteriocins, proteins, enzymes, and tea-derived phenolic compounds, may also be involved (Battikh et  al., 2013). The progression of the antibacterial activity of the polyphenolic fraction of Kombucha against enteric bacteria was investigated by Bhattacharya et al. (2016). It was demonstrated in this study that little difference exists in the susceptibility of Gram-negative

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enteric bacteria and Gram-positive Staphylococcus aureus (which was used in the study as a reference strain) toward 14-day fermented kombucha, its solvent extracts and the polyphenolic fraction (Bhattacharya et al., 2016). Kombucha beverage is reported to have demonstrated anticancer properties as well. According to a report by the Central Oncological Research Unit in Russia and the Russian Academy of Sciences in Moscow as revealed by population studies, daily consumption of kombucha broth appears to have a correlation with an extremely high resistance to cancer (Durfesne and Farnworth, 2000). The secondary metabolites in tea as well as the polyphenol compounds resulting from the fermentation has identified the responsible faction for this health benefit (Durfesne and Farnworth, 2000; Jayabalan et al., 2011). The enzymes, bacterial acids, and other secondary metabolites produced by the microbes during the fermentation process done in the preparation of Kombucha tea have displayed the ability to detoxify body (Greenwalt et  al., 2000; Watawana et  al., 2015a,b,c). Kabiri et  al. (2013) demonstrated that kombucha tea and silimarin effects drugs and other chemicals on the liver, where the fermented beverage seemed to offer comparatively higher protection and maintain the structural integrity of hepatic cells. Bhattacharya et  al. (2011) investigated the protective effects of kombucha tea against tertiary butyl hydroperoxide-induced cytotoxicity and cell death in murine hepatocytes. The fermented beverage was observed to be more effective than the unfermented black tea in reducing the cytotoxicity effects (Bhattacharya et  al., 2011). Jayabalan et  al. (2007) has hypothesized that this ability is mainly due to the capacity of glucuronic acid to bind with toxic molecules which enter the body and also the ability to increase excretion of these molecules from the physiology by the help of kidneys and intestines. In the study by Srihari et al. (2013a), lyophilized kombucha tea extract was shown to significantly decreased the survival of prostate cancer cells by downregulating the expression of angiogenesis stimulators such as matrix metalloproteinase, cyclooxygenase-2, i­nterleukin-8, endothelial growth factor, and human inducible factor-1α. It was also demonstrated in this study that kombucha was potent in inhibiting angiogenesis through alterations in the expression of angiogenic stimulators. Srihari et al. (2013b) was also able to demonstrate the antihyperglycemic effects of Kombucha in streptozotocin-induced diabetic Wistar rats. Gamboa-Gómez et al. (2016) investigated the angiotensin-converting enzyme (ACE) inhibitory activity of Eucalyptus camaldulensis and Litsea glaucescens infusions fermented with kombucha consortium. Although Camellia sinesis was not used as the substrate of fermentation in this instance, the ACE inhibitory activity was observed to have increased in

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both infusions, although it was lower in terms of its IC50 than positive control captopril. The study demonstrated that the kombucha-based fermentation has an influence on the concentration of phenolics and their potential bioactivity, thus resulting in the increased ACE inhibitory properties.

12.4  Compounds of Interest in Kombucha The bioactive compounds in kombucha exist due to their presence in the unfermented tea as well as the fermentation process, which is able to bio-transform polyphenol compounds. As stated previously, the bacteria and yeast also produce a number of other metabolites, including vitamins C, B1, B2, B3, B6, and B12, folic acid; organic acids, including gluconic, l-lactic, and glucoronic acids, and various enzymes (Miranda et al., 2016). Kumar et al. (2008) quantitative determined the presence of anions-fluoride, chloride, bromide, iodide, nitrate, phosphate and sulfate, in the kombucha broth using anion exchange chromatography with conductometric detection. The study also revealed that black and kombucha tea differ significantly in their anionic mineral composition. The various compounds—both bioactive as well as having the potential to impart health benefits (such as fiber) are discussed in detail herein.

12.4.1 Antioxidants An antioxidant is any substance, when present at low concentrations compared with that of an oxidizable substrate, which is able to significantly delay or inhibits oxidation of a particular substrate (Shebis et al., 2013). Tea on its own is known to possess antioxidant properties. Thus, during the kombucha fermentation, many compounds with radical scavenging properties are released from the tea leaves themselves (Greenwalt et al., 2000; Watawana et al., 2015a,b,c). Polyphenols and catechins are the main group of compounds which are found in tea belonging to the flavanol group, and are also known to thus exist in the kombucha beverage (Battikh et al., 2013; Malbaša et  al., 2011). Kombucha tea when prepared using green tea, black tea, and tea waste material has shown to possess a high radical scavenging activity (Jayabalan et  al., 2008). The concentrations of total polyphenols and flavonoids are also known to increase progressively with fermentation time in kombucha tea (Chakravorty et  al., 2016). Although the free-radical scavenging properties of the kombucha beverage shows time-dependent profiles, prolonged fermentation is generally not recommended because of the accumulation of organic acids (Jayabalan et  al., 2014). It is possible that these acids might reach harmful levels which would render the beverage unacceptable

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for direct consumption. As a future direction, the identification of extracellular key enzymes responsible for the structural modification of components during the kombucha fermentation and the identification of resulting potent metabolites responsible for the free-radical scavenging abilities are necessary to elucidate the metabolic pathway (Jayabalan et al., 2014).

12.4.2 Organic Acids The fermentation process of kombucha results in the production of organic acids, which increase with the exposure of the tea to the microbial cultures (Chen and Liu, 2000). The low pH of the beverage is also attributed to the production of various organic acids during fermentation (Chakravorty et al., 2016). The initial increase in reducing sugar content which was observed by Jayabalan et al. (2010b) may be attributed to the hydrolysis of sucrose to glucose and fructose by yeast. With the progression of the fermentation, the yeast utilizes the sugar anaerobically to produce ethanol (Chakravorty et al., 2016). In the course of metabolic activities which are ongoing during the fermentation process, yeast and bacteria in the tea fungus make use of substrates by different and complementary ways (Goh et  al., 2012; Srihari and Satyanarayana, 2012). Yeast cells hydrolyze sucrose into glucose and fructose by the enzyme invertase, and produce ethanol via glycolysis (Srihari and Satyanarayana, 2012). On the other hand, the acetic acid bacteria utilize glucose to produce gluconic acid and ethanol to produce acetic acid (Srihari and Satyanarayana, 2012). Other acids that have been previously reported were glucuronic acid and lactic acid (Jayabalan et al., 2007). However, in the system utilized by Chakravorty et al. (2016), neither of these two acids has been detected. It was hypothesized by Chakravorty et al. (2016) that this difference in the composition of this particular kombucha tea variety may have been due to the overall distinction in the microbial community and/or the varying lengths of fermentations for that particular kombucha brew. The composition of the organic acids present in the liquid broth eventually determines the flavor and taste of tea fungus products (Chen and Liu, 2000). In addition to the concentrations of residual sugars and carbon dioxide, organic acids—especially the ratio of acetic acid to gluconic acid imparts a tart taste to the beverage (Chen and Liu, 2000). Volatile acetic acid produces an astringent and acidic flavor, while the flavor produced by gluconic acid is mild (Reiss, 1994).

12.4.3 Fiber Cellulose is the primary form of fiber present in the kombucha tea fungal mat. In the food industry, bacteria-based cellulose is used as food matrices, thickeners, dietary fibers, stabilizes, and binders

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(Watawana et  al., 2015a,b,c). In addition, for industrial applications, this bacterial cellulose is preferred in instances where plant-based cellulose cannot be used (Watawana et al., 2015a,b,c). The primary producer of cellulose in the kombucha consortium is Gluconacetobacter xylinum (Teoh et al., 2004). The pellicular formation observed during the kombucha fermentation process is the mass of cellulose produced by G. xylinum and also contains comparatively lesser amounts of hemi-cellulose as well (Jayabalan et al., 2010a). Glucose liberated from sucrose is metabolized for the synthesis of cellulose and gluconic acid by Gluconacetobacter strains (Sreeramulu et al., 2000). Cellulose prepared from pellicles of G. xylinum has a unique characteristic in terms of its chemical stability, molecular structure, and mechanical strength (Czaja et al., 2006; Jayabalan et al., 2014). It has been reported that the caffeine and related xanthines found in tea have the ability to stimulate the synthesis of this cellulose production by the bacteria (Durfesne and Farnworth, 2000).

12.4.4  Determination of Bioactivity As mentioned previously, kombucha has been consumed in many countries for a very long time and thus has a lengthy history in terms of usage and consumption. Many benefits for health have been reported based on personal observation and testimonials while studies on the bioactivity of the beverage have only started to commence recently. It has been reported that many therapeutic effects of kombucha tea may be due to the presence of substantial amounts of glucuronic acid, usnic acid, and lactic acid—in particular glucuronic acid (Pauline et  al., 2001). Glucuronic acid is well known in an important process for detoxification and excretion of exogenous chemicals called glucuronidation (Nguyen et  al., 2014). In the study by Nguyen et  al. (2014), the presence of Lactobacillus casei and Lactobacillus plantarum were observed to have improved and increased the production of glucuronic acid in kombucha tea. Other than the organic acids, the presence of tea catechins also makes the kombucha beverage a noteworthy functional food. Overall, many of the plants consumed by humans contain thousands of phenolic compounds. Basically, tea from Camellia sinensis is considered as a functional food and is the most widely consumed beverage in the world, second only to water (Chen and Sang, 2014). Other than the typical preventive properties of hindering the biochemical processes leading to noncommunicable diseases such as diabetes, cardiovascular disease, and cancer, polyphenols existing in teas have been identified to exhibit starch hydrolase inhibitory activities (Chaudhry et al., 2014). The most important and characteristic tea polyphenols which are present in Kombucha are the flavanols of which catechins (flavan3-ols) are predominant. Other major tea polyphenols are picatechin

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(EC), epicatechin gallate (ECG), epigallocatechin (EGC), epigallocatechin gallate (EGCG), catechin (C), and gallocatechin (GC) (Durfesne and Farnworth, 2000). Tea contains also contains flavonols, mainly quercetin, kaempferol, myricetin, and their glycosides (Durfesne and Farnworth, 2000). In a recent report by Kovacevic et  al. (2014), it was shown that kombucha tea has potential to revert the CCl4-induced hepatic toxicity. This further confirmed the findings of the study by Murugesan et  al. (2009). It was hypothesized in this study that the antioxidant molecules produced during the kombucha fermentation period could be the reason for the efficient hepatic protective and curative properties against CCl4-induced hepatic toxicity (Kovacevic et  al., 2014). However, if the beverage is used in excess, it was also suggested that it may result in an overdose and induce toxicity on its own.

12.5  Application of the “Tea Fungus” for the Production of Other Types of Functional Foods and Beverages The kombucha tea fungal mat has been recently used for the fermentation of various beverages which are not necessarily C. sinesis based. The fermentation process itself leads to several modifications of the final drink composition with biotransformation, secretion, and/ or degradation of many components (Battikh et al., 2013). Thus, the resulting kombucha beverage has a metabolic composition which is different yet related to the original substrate. Based on this reasoning, Watawana et  al. (2015a,b,c) used the tea fungal mat to ferment coffee. This study was innovative since coffee is a beverage which has a commercial value throughout the world, and is second only to tea in terms of consumption. Similar to C. sinesis-based sweetened tea which is typically used for the fermented preparation of kombucha, in this study as well, fermentation with tea fungus would have been able to convert the added sugar in the sweetened coffee into organic acids and ethanol. Similar to tea, coffee would have also been able to provide necessary nitrogen sources for the tea fungus culture (Watawana et al., 2015a,b,c). The fermentation of sweetened oak herbal infusions (Quercus resinosa) with the kombucha consortium was explored by Vázquez-Cabral et  al. (2014). The study demonstrated that the metabolic consumption of flavan-3-ols and hydroxybenzoic acid derivatives, as well as the production of organic acids (succinic acid) has decreased the astringency and bitterness of the substrate, improving the product’s quality and acceptability. A higher sugar content was also observed, which had further improved the sensory properties of the fermented product.

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Watawana et al. (2015a,b,c) used the kombucha tea fungal mat to ferment king coconut water. Recent evidence suggested that king coconut water possesses functional properties which are associated with many health benefits. For instance, Leong and Shui (2002) highlighted that the water of the fruit C. nucifera L. arecaceae had demonstrated antioxidant properties. The study demonstrated an enhancement of the antioxidant and starch hydrolase inhibitory properties of king coconut water as a result of the kombucha-based fermentation. Essawet et al. (2015) analyzed samples of Kombucha-based fermentation broths enriched with CoffeeBerry extract. Among the bioactive compounds present in investigated samples by Essawet et  al. (2015) chlorogenic acid was the predominant. Velicanski et al. (2013) tested the possibility of obtaining kombucha pellicle-based fermented beverages from medicinal herbs belonging to Lamiaceae family: Lemon balm, thyme, peppermint, and sage. In the case of lemon balm and peppermint tea, the study demonstrated that the fermentation process had to be shortened for 1 or 2 days compared with a traditional substrate made of C. sinesis. Acetic acid was observed to be the dominant organic acid present in all beverages obtained from the study (Velicanski et al., 2013). The study by Liamkaew et al. (2016) investigated on the use of apple juice together with black tea as substrates to produce kombucha beverage in order to improve the quality of the beverage and assess foodborne pathogens for commercial production development. The results of this particular study demonstrated that using apple juice as the culture substrate together with black tea improved total phenols content when exposed to the kombucha tea fungal consortium. Liamkaew et al. (2016) observed this new beverage as a novelty since there is no kombucha product which has been developed to date using fruit juice combined with black tea. Akbarirad et  al. (2017) obtained kombucha vinegar by fermentation of the kombucha broth layer on sweetened pasteurized fruit juices (pomegranate, red grape, sour cherry, and apple). The study demonstrated that as the fermentation continues, the actual concentration of acids, pH value, fructose content, and biomass yield statistically significantly increased (P < 0.01), although the alcohol and residual sucrose content decreased in all the juices. The study displayed the versatility of the kombucha vinegar in that it could be used even to ferment fruit juices. Dairy products have also been the substrate of fermentation incorporated with the kombucha consortium. Hrnjez et al. (2014) investigated the chemical quality and protein profile of new fermented dairy products obtained by kombucha starter culture at different fermentation temperatures. Results from this study indicated that fermented dairy products produced by kombucha at 37°C and 42°C could be less allergenic than milk and more suitable for special allergenic nutrition

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and thus, these products could be proposed for special nutrition for consumers with proteins allergies (Hrnjez et al., 2014). In the study by Gamboa-Gómez et al. (2016), physicochemical properties, consumer acceptance, antioxidant, and ACE-inhibitory activities of infusions and fermented beverages produced from the incorporation of kombucha microbial consortium of E. camaldulensis and L. glaucescens were compared. The fermented products had enhanced antioxidant and ACE-inhibitory activities and E. camaldulensis as well as L. glaucescens can be considered as natural substrates containing biocompounds to be used for fermentation with the kombucha tea fungal mat. The safety of the fermented beverages needs to be borne in mind when it comes to the product development aspects. According to Ernst (2003), consumption of kombucha tea alone has been associated with serious adverse effects. However, it is mentioned in this review that these are isolated reports which cannot form the basis for any generalizations (Ernst, 2003). The evidence is based on case reports and case series none of which were reported in sufficient detail to allow firm conclusions about a cause–effect relationship (Ernst, 2003). Overall, it would seem apparent that depending on the method of preparation and standards of hygiene, kombucha teas may be entirely innocent of any toxicological effects, while others carry the risk of contamination and infection—all of which are eventually based on the preparation methods being followed. Additionally, the characteristics of tea fungus-based beverages are entirely based on the fermentation time. Although increased fermentation time appears to produce many bioactive compounds of interest in all analyzed beverages to date, it is imperative to assess the presence of toxic compounds and their amounts in order to ensure complete deprivation from adverse effects of consuming the fermented product.

12.6  Kombucha as a Symbiotic Functional Food Kombucha beverage is also called as symbiotic culture of bacteria and yeast (SCOBY). As previously mentioned, kombucha is produced by the symbiotic culture of yeast and bacteria which makes “tea fungus” (M. gisevii Lindau). Osmophilic yeasts and acetic acid producing bacteria live together symbiotically to convert the tea to kombucha tea through fermentation. Yeasts in particular, convert added sugar in tea to organic acids and ethanol, and acetic acid bacteria uses ethanol to produce cellulose fiber during the fermentation period. Over the period of fermentation time, the cellulose fibers bundle together to form a jellyfish-like zoogleal mat in which the yeast and bacterial cells are attached. Kombucha is being used by humans as a probiotic

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drink for healing and health prophylaxis effects (Kozyrovska et  al., 2012). The word symbiotic is sometimes confused with the word synbiotic through both words means quite similar concepts. The word “symbiotic” is derived from the symbiosis which means “the existence together based on mutual cooperation.” The word “synbiotic” means the “the existence of both probiotic microbes and prebiotic molecules together in food systems.” Both words apply to kombucha as there is symbiosis existing between yeast and bacteria as well as the presence of both probiotics and prebiotic molecules in kombucha. Symbiotic and synbiotic foods are gaining popularity among health-conscious consumers due to their various beneficial effects on lipid metabolism, and other yet to be proved clinical effects. Synbiotic foods are defined as “a mixture of prebiotics and probiotics that beneficially effects the host by improving the survival and implantation of live microbial dietary supplements in the gastrointestinal tract by selectively stimulating the growth and/or by activating the metabolism of one or a limited number of health-promoting bacteria, and thus improving the health of the host” (Gibson and Roberfroid, 1995). There are no clear studies explaining the probiotic characteristics of microbes fermenting tea to produce kombucha. However, there are some claims to prove that the kombucha microbes might be probiotics also. Symbiotic and synbiotic components of kombucha tea are given in Fig. 12.3. Yeasts and acetic acid bacteria are fermenting the tea to produce kombucha are tolerant toward acidic pH which is the main criteria for microbes to be called as probiotics. pH of kombucha during fermentation is reduced from 4.0 to 2.0 (Jayabalan et al., 2016a,b). Microbes producing kombucha tea are expected to be resistant toward bile and reach the colon and grow there. Ultramicroscopic cellulose fibrils (microcellulose) might be available in the kombucha beverage. This is claimed that the thick cellulose film is formed by the action of acetic acid bacteria during kombucha fermentation. Cellulose is the waste product of acetic acid bacteria and is produced as microcellulose which is bundled to make the think cellulose film. Microcellulose available in the kombucha

Fig. 12.3  Kombucha as functional symbiotic/synbiotic beverage.

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beverage acts as a prebiotic component. Cellulose being an insoluble dietary fiber helps in digestion by trapping water in the colon. The trapped water keeps the stool soft and bulky which promotes the regularity and prevents constipation. However, cellulose is partially or less-well fermented by the bacteria living in the colon (Tungland and Meyer, 2002). Kombucha tea and the tea fungus mat can be a promising probiotic and prebiotic formulation for the following reasons (Kozyrovska and Foing, 2010): i. Kombucha is a source of both probiotic (bacteria and yeast) and prebiotic (microcellulose) and can be called as synbiotic. ii. Kombucha provides short-chain fatty acids (SCFAs) and other metabolites which boost the immunity. iii. Kombucha starter is practically immortal and can be activated when required. iv. Kombucha is reported for its multiple healing effects and as an energizer. Kombucha can be called as a functional food due to the following reasons: i. presence of tea polyphenols, ii. presence of very less concentration of ethanol which is <0.5%, iii. production of bioactive compounds (yet to be identified) through the fermentation process, iv. presence of many other bioactive compounds in flavored kombucha due to the addition of spices and herbs, fruit and flower extracts, etc., and v. presence of thin cellulose fibers in the drinkable part of kombucha (not the thick tea fungus) which can act as prebiotics for the bacteria living in the colon (yet to be explored). Being a symbiotic and synbiotic functional food, kombucha is believed to exert several biological effects in human body. Kozyrovska and Foing (2010) and Kozyrovska et al. (2012) have reported that kombucha tea and tea fungus can be a promising formulation of a probiotic and prebiotic for extreme expeditions like space travel of astronauts due to its symbiotic and synbiotic nature.

12.7  Upscaling the Kombucha Fermentation Process Kombucha is produced through a fermentation process which has been followed in many countries—mostly of Asian origin, for centuries. Most of the fermented products are manufactured through large-scale production in food industries. However, kombucha production involves homely fermentation where there is no need of any specialized fermenter or bioreactors. Production of kombucha needs merely a large vessel with a cover and provision to withdraw samples

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to taste during the fermentation period. Kombucha fermentation is static hence it does not require the impeller for mixing. Kombucha fermentation is aerobic, but sparging the air through sparger does not allow the formation of cellulosic pellicle; thus, the sparger is also not required. Kombucha fermentation mostly happens between 20°C and 25°C, which needs a temperature controller. The temperature of the fermentation room can be controlled well by using an air conditioner so that the temperature controller is not fixed with the fermentation vessel. The fermentation vessel can be of any volume with large surface area to promote the growth of the cellulosic pellicle which will be used to start the next batch of fermentation. A fermentation vessel made of glass is highly desired due to the leaching of metals and plastics owing to the acidity produced during fermentation.

12.8  Global Market of Functional Foods and Beverages Despite the difficulties in defining the term functional food and the limitations on its possible health-related effects, consumers have found functional food products interesting and useful. Functional foods are considered as foods consumed by only upper-class people, especially those who have a high disposable income. Revenues generated from the food and beverages market worldwide reached 7.8 trillion USD in 2013. Due to the increase in aged populations and awareness about healthy foods, the production of functional foods and beverages is kept increasing. Functional foods and beverage market are one of the fastest growing sectors in the food industry with annual growth rates of 6%–10%. The global functional foods and beverage market was estimated to be 32 billion USD in 1999 (New Nutrition, 2002) and projected to be 130 million USD by 2015 with the market for functional food and ingredients estimated to reach 2.5 billion USD by 2020 (Corbo et al., 2014; Nutraceuticals World, 2015). Among the functional foods, functional beverages are the most popular functional foods due to their convenience of handling, ease of distribution and storage, and opportunity to incorporate desirable nutrients and bioactive compounds (Stones, 2015). The modern perspectives of consumers in the developed world are the driving factors for the market of functional foods and beverages. They are listed as follows: i. foods with novel proteins which are sustainably produced, ii. less processed and more natural foods and drinks, iii. concern about the environment, iv. recognition that diets influence the way consumer look and feel, and v. sports nutrition.

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To satisfy the demands of the health-conscious consumers, the leading world’s top 61 food and drink companies have collectively invested 10.8 billion USD only in research and development to innovate the new foods and beverages in 2012 (Sloan, 2012). Research and development in the functional food sector mainly involves know-how and process improvements to the existing ingredients rather than innovating new ingredients. This is due to the remarkable higher regulatory cost involved in getting approval and functional claims permitted for a novel food. Research on traditional foods has also been increased recently due to their safety and efficacy of the ingredients available in them as a source of leads for bioactive compounds. A few large companies have started to focus on environmental and social sustainability as “green” and “local” are becoming more important to consumers (European Commission, 2013–2014). Japan is considered to be the world’s major market of functional foods, trailed by the United States. European markets still appear to be less established. The total sales from these three leading markets contribute to over 90%. The UK, Germany, France, and Italy are the major markets of the European Union in this aspect. The European market is considered to be a heterogeneous market, categorized by huge regional variations in use and acceptance of functional foods. As for Italy, 4% of the whole Italian sector is covered only by “health yogurt” which has a growth rate of 6.3% per year and attaining 560 million euros of sales. Functional Food market of Poland, Russia, and Hungary are still emerging, and numerous novel functional foods are launched in the last few years. It is possible to reduce the risk of some diseases and attain energy balance and a healthy weight by following this recommendation and avoiding sedentary lifestyle. The global market for functional food keeps increasing due to the extensive coverage by media about the diet-related diseases and their influence on health and well-being of communities. Functional food is being developed throughout the world to fulfill the demand from consumers for healthful food. Due to the consumer drivers, the food industries are reformulating the food products to increase the physiological functionality of inherent nutrients or by adding bioactive with largely clinically proven physiological function (Vincentini et al., 2016).

12.8.1 Global Market of Kombucha and Its Future Directions The demand for kombucha is high in developed markets, particularly in the United States and other countries in Europe. North America is the most significant market for Kombucha. In North America, US contributed the largest share of the kombucha market. The Americas accounted roughly 51.16% of its entire sales worldwide in 2016.

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Commercially bottled ready-to-drink kombucha became readily available in the United States during the late 1990s. Kombucha was ranked as the top-selling fermented drinks in the United States and is fastest growing food trends with revenue of 180 million USD in 2015 (Kombucha-Statistics and Facts, 2015). The global market for kombucha is estimated to reach about 1.8 billion USD by 2020 at a CAGR of 25.0% from 2015 to 2020 (Kombucha Market Research Report, 2016). The global market for kombucha was valued at around 1062 million USD in 2016 and is expected to reach approximately 2457 billion USD by 2022, growing at a compound annual growth rate (CAGR) of about 25% between 2017 and 2022 (Zion Market Research, 2017). Zion Market Research (2017) has estimated that the global kombucha market will grow at a CAGR of 14.57% during the period 2017–21. According to Technavio Market Research Analyst (2017), global kombucha market is expected to grow steadily at a CAGR of above 14% by 2021. Markets and Markets (2017) estimated that the worldwide kombucha market is to increase from 0.6 billion USD in 2015 to 1.8 billion USD by 2020, at a CAGR of 25% from 2015 to 2020. The rising population in Asia-Pacific and as an originator of kombucha drink, the region is expected to be the fastest-growing in the global market for kombucha. The demand for usage of kombucha is expected to grow at a decent pace in Germany and Japan, whereas the high growth of kombucha market is experienced in India and other Asia-Pacific countries. Latin America is expected to show moderate growth in coming years. Strong demand for kombucha drinks coupled with considerable economic growth in countries such as Brazil, Venezuela, and Argentina is anticipated to boost demand in the region in the years to come (Zion Market Research, 2017). The demand for the beverage is ever increasing, with the rising awareness among the consumers about the benefits of the drink. Following are the factors driving the global market of kombucha: i. ease of manufacturing, ii. changing lifestyle, iii. increasing disposable income, iv. growing health concerns, v. trend of maintaining healthy diet, vi. rising incidences of chronic diseases (cardiovascular diseases, diabetes, high blood pressure, etc.), vii. increasing awareness about probiotics, prebiotics, and synbiotics, viii. increased acceptance levels for fermented beverages and its use as an alternative to soda, ix. increasing demand for the probiotics and functional beverages, x. availability of different flavors (herbs and spices, citrus, apple, coconut, mango, flowers, etc.) of kombucha,

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xi. increasing consumer awareness of the negative impacts of synthetic products on health and the environment, and xii. competition among the leading kombucha manufacturers. Carbon dioxide produced during kombucha fermentation produces fizzy bubbles and makes the kombucha beverage as a “naturally carbonated fizzy drink.” The fizzy nature of kombucha attracts the consumers to use it as a healthy alternative to soda (Technavio Market Research Analyst, 2017). The primary factor hindering the growth of kombucha market is the issues related to the alcohol content of kombucha. US Alcohol and Tobacco Tax and Trade Bureau has recently started to scrutinize the alcohol content in commercial kombucha due to its increasing popularity (Research and Markets, 2017). Following are some of the other hindering factors for the kombucha market: i. rapidly changing consumer demands and preferences, ii. rapidly changing consumer spending pattern, iii. consumer tastes, iv. regional, national, and local economic condition, and v. demographic trends. Kombucha market is segmented by the following (Transparency Market Research, 2017): i. type of microorganisms used (yeast, bacteria, mold, and others), ii. flavors (citrus, herbs and spices, berries, coconut and mangoes, apple, flowers, and others), and iii. geography (North America, Europe, Asia pacific, and Rest of the World). There are numerous new domestic and international companies manufacturing kombucha. It is manufactured and sold commercially mainly by GT’s Kombucha Company, Reed’s Inc., Live Soda Kombucha, Kombucha Wonder Drink, Kombucha Kamp, Millennium Products, Health-ade, Kosmic Kombucha, Makana Beverages Inc., NessAlla Kombucha, Red Bull GmbH., Buchi Kombucha, Celestial Seasonings, KeVita, Inc., American Brewing Company, Equinox Kombucha, healthy Brands Collective, MOCU Health, OREGONIC TONIC, Love Kombucha, Revive Kombucha, Tonica Kombucha, WILD TONIC, and others (Zion Market Research, 2017). Several established beverage brands are also trying to enter into this market. Due to the presence of several established and local kombucha manufacturers, the global kombucha market is highly fragmented. There is a huge competition among the manufacturers based on the price, quality, innovation, reputation, and distribution. Some of the major companies have now started to expand to new geographical regions and segments for more adaptability regarding new technologies and to increase their customer bases (Research and Markets, 2017). Because of its health benefits, governments in several countries are taking initiatives for

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manufacturing, marketing, and regulating the production and consumption of kombucha. Manufacturers launch different exotic flavors of kombucha regularly to keep the kombucha market active. The flavored kombucha market recorded the most substantial demand in 2015 and is expected to grow the fastest by 2024. Among the flavors available, herbs and spices, and coconut held the highest share of the total market regarding the revenue in 2016. The citrus flavor is also one of the top-selling drink. Kombucha is now available in almost 30 different flavors and is expected to have kombucha flavored with turmeric and ashwagandha. Kombucha is also sold in two main categories namely, organic, and nonorganic. Organic kombucha dominated the kombucha market during 2016 and accounted for a major part of the overall market share (Technavio Market Research Analyst, 2017). Kombucha beverage is available in retail stores, supermarkets, organic stores, and in health stores. Retailers sign an agreement with brewers for the distribution of kombucha drinks. Sales of kombucha in online stores are expected to grow shortly. Kombucha is also considered as the 21st-century yogurt which will be booming as multi-billion-dollar industry in the future like the general yogurt industry. Stringent regulations will be developed by several governments around the world to monitor the kombucha market. It is evident that kombucha market is going to be very strong with the introduction of the online market, new laws to control the market and fresh exotic flavors and kombucha beers (Troitino, 2017).

12.9 Conclusions Kombucha is sometimes claimed as a miracle drink by the people those who consume it regularly. Drinking kombucha may give health benefits when the consumer has some illness, while consuming the beverage targeting the disease may not provide any health benefits to the consumer who is already healthy. Regular kombucha drinkers may overhype the benefits that they are observing to promote their neighbors, friends, and relatives to the consumer it. Recently kombucha is being taken by cancer patients who are undergoing chemotherapy, and it is found to be improving the chemotherapy results. Despite the fact that there are no precise human clinical studies to prove the beneficial effects of kombucha, it has gained the popularity as a refreshing, functional, and synbiotic beverage. Tea polyphenols, organic acids and the yet to explore compounds produced during the fermentation period are the bioactive components of kombucha beverage and the reason for the kombucha to be called as a functional food. Kombucha is being prepared mainly in home-scale manufacturers without using

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any specialized equipment like fermentor or bioreactor and is mostly sold in retail and organic stores. In recent days, kombucha is available in several flavors which are prepared from spices/herbs, fruit and flower extracts. Culture or SCOBY of kombucha is sold online which helps the people to start the kombucha fermentation. It is expected that kombucha will gain market as yogurt throughout the world soon and will be available in online stores. The detailed research will produce new market and renaissance which will help to use kombucha as a pharmacological drink. Through post-genomics it will be possible in future to engineer the kombucha microbiota to interact with the individual gut microbiota and system to catabolize cholesterol and to produce the valuable biological in the human gut. Based on the knowledge provided by kombucha, mutually cooperating robust synthetic ecosystems composed of yeast and bacterial strains, like CoSMO (for cooperation that is synthetic and mutually obligatory) may be constructed for healing purposes.

Acknowledgments Author R. Jayabalan acknowledges the support given by DST (SR/FT/LS68/2012) (SERB/F/5150/2012-13), and Department of Biotechnology (BT/PR6486/ GBD/27/433/2012), Ministry of Science and Technology, Government of India for the financial support.

Conflicts of Interest The authors declare no conflicts of interest, financial or otherwise.

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446  Chapter 12  Kombucha as a Functional Beverage

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Further Reading American Dietetic Association (ADA), 1999. Functional foods-position of the ADA. J. Am. Diet. Assoc. 99, 1278–1285. Food Drink Europe, Data and Trends in the European Food and Drink Industry, 2013–2014. http://issuu.com/fooddrinkeurope/docs/data_trends_of_the_european_food_/11?e=0. Jayabalan, R., Swaminathan, K., 2016. Biochemical and Therapeutic Properties of Kombucha Tea. Lambert Academic Publishing, Germany, ISBN: 978-3-659-95358-3. Mazza, G., 1998. Functional Food, Biochemical and Processing Aspects. Technomic Publishing, Lancaster, PA, p. 437. Wildman, R.E., 2001. Handbook of Nutraceuticals and Functional Foods. CRC Press, Boca Raton.