Kombucha is a fermented tea drink with a slight fizziness due to carbonation. It is stated by officionados to quite categorically have a flavour similar to cider and champagne. That flavour depends very much on the type of tea used and its taste is far removed from what we would think a fermented tea would be expected to taste like. Why harp on about its flavour ? Probably because adherents to its nutritional properties have absolute belief in its restorative powers even though claims for its efficacy are not yet firmly cast.
Konbucha is thought to have originated in China and has been consumed there for over 2000 years. The first records come from 221 BC where it was known as ‘The Tea of Immortality’. The history relating to its benefits come mainly from anecdotal evidence as is often the case with many traditional products. It is also known by various other names inlcuding haipao, kocha kinoko, homgo, suancha or takezutsu-sancha.
Kombucha has certainly achieved popularity amongst many for its health benefits resulting from regular consumption. It should be thought of as a probiotic drink to rival yogurts and smoothies.
The beverage is said to stimulate digestion, the immune system, to improve liver function, provide detoxification and even reduce obesity and help with weight management. It is also believed to be a treatment for various chronic and acute conditions like arthritis to cancer, osteoporosis, for treating high blood pressure, neurotoxicological complaints and so on (Dufresne and Farnworth, 2000). A large Russian study claimed in the early 50s claimed that daily consumption of kombucha was correlated with a high tolerance to cancer although this remains to be proven by other studies. Unfortunately, definitive clinical studies are needed to demonstrate many of the putative health benefits.
Production & Fermentation Microbiology
Generally, kombucha is prepared by fermenting black tea which has been sweetened with sugar. In the process which can be performed at home as well as industrially, black tea leaves are infused with boiling water that is sweetened with sugar such as sucrose at a concentration between 50 and 150g/L. The whole brew is left to infuse for at least 10 minutes.
After removing the tea leaves, the brewed tea is poured into a wide-mouthed sterilized and clean vessel. it is then acidified by adding vinegar or the so called tea fungus.
The tea fungus contains a variety of highly beneficial yeasts and bacteria and molds. This starter culture is often known as a SCOBY (symbiotic colony of bacteria and yeast). The SCOBY can be viewed as a form of probiotic culture although this is a misnomer. The manufacture of kombucha relies on bathing black or in some cases, green tea with a culture of SCOBY which looks like a rubbery disc or “mushroom”. That rubbery disc is in fact a floating cellulose mat or cellulose pellicle. It is formed from the yeast and bacteria from a previous fermentation.
The equipment used in the home consists of a highly sterilized glass jar for the fermentation and a coffee filter or weave cloth to filter out the bacteria. The jar is carfully covred with a clean cloth. The tea is fermented in the jar in a warm place for up to about a month although it is often ready between 10 and 12 days. The kombucha needs to be tasted at various stages to check flavour and sweetness. Some of the SCOBY should be retained for use in the next batch.
The SCOBY cultures can be used over a number of times. The fermentation medium can also include various types of water but usually spring water, cane sugar with distilled white vinegar to reduce the pH.
The products produced by fermentation include a variety of food acids including acetic acid (vinegar), vitamins, minerals, tea compounds and gluconic acid. The beverage is also slightly carbonated as the yeasts ferment the sugar as in a wine fermentation. Caffeine is retained in the brewing mix. The cider flavour is probably due to the presence of gluconic acid with other yeast based compounds mixed in.
The product really lends itself well to product development with a variety of flavours now available. We discuss the brands later on.
A powerful symbiotic relationship is created between the yeast and the acetic acid loving bacteria. This combination effectively inhibits the growth of any other micro-organisms including the growth of contaminating bacteria. The bacteria is mostly Lactobacillus with Acetobacter and the changes they produce are now well understood (Teoh et al., 2004; Jayabalan et al., 2007). Acetobacter xylinum was found to be the predominant bacterium in the mat. It produces both acetic and gluconic acids although a mix of bacterial species are found which all contribute their own unique flavour. You can understand why it is important to look after your SCOBY as it may be unique to you and your product. The A. xylinum also synthesizes the floating cellulosic network which is essential for the close relationship to form between it and the yeasts.
The yeasts incidentally are many and varied. We see Zygosaccharomyces kombuchaensis, Z. bailii, Z. bisporus, Z. microellipsoides, Brettanomyces, various Saccharomyes, Schizosaccharomyces pombe, Torulaspora delbrueckii, Rhodotorula mucilaginosa, Candida stellata and Brettanomyces bruxellensis. This range of yeasts have all been isolated from different SCOBY.
The latest market research from Technavio shows the global kombucha market will grow by almost 15% (CAGR) from 2017 to 2021. Much of this growth is in the USA in trendy markets where it is projected to reach $1.8 billion globally by 2020. The current market is $1.2 billion worldwide. The market can be split into two product types, organic and non-organic. In 2016, the organic kombucha segment accounted for 95% of the market. The Chinese are the largest consumers of the drink in the East but this may be due to the development of the drink from this country.
Product Development Opportunities With Kombucha
Kombucha lends itself very well to the addition of juices. There has been plenty of activity in the market place with the launch of various drinks that combine kombucha with certain fruit juices that have various health properties. Suja Life LLC (Oceanside, California) now offer organic Kombucha which expands its range of beverages in this market. Their four products could be seen on the shelves in 15.2-ounce bottles. The Suja Life products are non-GMO and non alcoholic. They also use high pressure processing to pasteurise the product which extends shelf-life.
The business claims the drinks contain 5 billion colony-forming units of probiotics with several functional adaptogens. Looking at The main health claim is ‘supports immune health’.
The lineup is offered in six varieties:
- Mixed Berries Kombucha, which includes the adaptogen schizandra
- Peach Ginger Kombucha, which features the adaptogen reishi;
- Ginger lemon Kombucha, which is made with the adaptogen, ashwagandha;
- Super Green Kombucha, which contains the adaptogen moringa
- Pineapple Passionfruit Kombucha, with turmeric
- Green Apple Kombucha with amla.
The Green Apple Kombucha for example has a simple ingredient list of water, kombucha, apple juice, cane sugar, lemon juice and amla. The bacteria is inactivated Bacillus coagulans and the probiotic Lactobacillus rhamnosus. The Ginger lemon flavour appears to have a good balance between the two – a sharpness of lime citrus overlaying the cider-like notes. It seems clean and refreshing.
In Portland, Oregon in the summer of 2018, I was perusing the retail shelves and noticed quite a variety of products. Revive from Sonoma County in California have an extensive range too. There flavours include ginger and lime, an original cola, the hibiscus refresher and a turmeric, ginger and citrus flavoured kombucha. Mind you they also offer yerba mate with ginger, a mocha java coffee, a cucumber mint with lemon, a valencia orange & cayenne, a lemon refresher and last but not least a toasty green tea. That’s quite a collection.
Mind you if you think that isn’t big enough then try GT’s Living Foods trio of flavours from each of these four groups, Enlightened Kombucha, Enlightened Synergy, Classic Kombucha and Classic Kombucha. There are a total of 12 flavours on current standing and these really have made full use of herbs, spices, vegetable juices and much more. GT’s Living Foods is based in Beverly Hills, California.
I like Health-Ade who make the claim that there branded products are the slowest to ferment. Presumably this adds to the unique flavour in their products. they too have a flavoursome product range. I noticed a Christmas product, Holiday Cheers which a is a brew blending ginger, allspice, chocolate and more. Two other leading brands from Oregon are Brew Dr which also has a large selection to choose from and is based in Tualatin. We also have Lion Heart which is brewed in Portland, Oregon. Given the microbrewery scene over there it is not surprising they could put their fermentation skills to good use preparing this product.
In the United Kingdom we now have Go! kombucha. These products have a sophisticated appeal in screw-top wine bottles (750ml) and emphasize the type of tea fermented. They currently have Green Secha, Red Pu-Erh, China White, Yunnan Gold and Darjeeling Black. That’s also quite a clever play on colours too. The sugar content is about 4g/100ml and the energy content is between 16 and 17 cals/100ml.
I apologise to anyone I’ve missed and I would welcome the opportunity
to include you in the list. In due course I intend to do a more thorough review of the brands because of the great range of flavours on offer.
- Do not consume if pregnant or breastfeeding.
- If you have a compromised immune system.
Few clinical studies are known which have actually demonstrated its safety, efficacy or indeed health benefits. Various stomach complains such as nausea, dizziness and stomach ache have been reported so care is needed especially with over-consumption. Keeping the fermentation going for too long can lead to a build up of organic acids in the brew. However, it is likely that this will produce too acidic tasting a product for consumption. Dilute the product if it tastes too acidic.
Always see your GP if you are concerned about introducing kombucha into your diet, or if you have any adverse side effects after consuming it.
Product Technology For Making Kombucha At Home
SCOBY discs can be purchased from Happy Kombucha to produce about a litre of fermented tea and is certified to be organic.
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Dufresne, C., & Farnworth, E. (2000). Tea, Kombucha, and health: a review. Food Research Int., 33(6), pp. 409-421
Jayabalan, R., Marimuthu, S., & Swaminathan, K. (2007). Changes in content of organic acids and tea polyphenols during kombucha tea fermentation. Food Chemistry, 102(1), pp. 392-398.
Teoh, A. L., Heard, G., & Cox, J. (2004). Yeast ecology of Kombucha fermentation. International Journal of Food Microbiology, 95(2), pp. 119-126.