The latest buzz word is Kombucha. Do you know what it is, and is it really that good for you?
It is made from fermenting black or green tea using a culture of bacteria and yeast, and is consumed for its functional purported probiotic health benefits. It is believed to have originated in Northeastern China. It can be brewed at home or bought commercially, but due to the alcohol content which will vary in the drink, it can be regulated in some countries.
SCOBY is an acronym for ‘Symbiotic Culture Of Bacteria and Yeast’. It is the product of the bacteria in the brew, which create strands of cellulose that weave together. This mat of bacterial cellulose is safe for all living things and even edible. It may sink or float and may end up anywhere in the brew, depending on how much CO2 gas is trapped between the layers. The new Kombucha SCOBY will form across the top of the brew at the air and liquid interface. The symbiotic culture of yeast and bacteria involves anaerobic ethanol fermentation from the yeast (the yeast converts the sucrose into glucose and fructose and produces ethanol) (1), and anaerobic organic fermentation and aerobic ethanol oxidation to acetate by the bacteria (2). This symbiotic relationship of yeast and bacteria inhibits the growth of any potentially contaminating mould or bacteria (1). The fashion design department at Queensland University of Technology is even trialing vegan leather garments made out of SCOBYs (4).
The culture is put into sugared tea, and then the sucrose is converted into different the acids by the yeast. The pH of the drink is usually less than 3, and if it is over-fermented it can be too acidic like vinegar. The main microbiota of the fermented drink are AAB (acetic acid bacteria) and yeast, and sometimes LAB (lactic acid bacteria). The microbiota of the SCOBY will differ depending on the origin of the culture, the fermentation time, and the temperature of the tea. Different raw materials (black or green tea) will create different bioactive components in the final product.
There is a lack of research in health benefits in human trials, however the beneficial effects of the tea are attributed largely to tea polyphenols, gluconic acid, glucuronic acid, lactic acid, vitamins, amino acids, antibiotics and micronutrients (1-3). Various studies have looked at the Vitamin C content of the tea, antimicrobial activity, antioxidant, and glucuronic acid (detoxifier) and glucaric acid (cholesterol lowering effect). More research is required to determine the different cultures that can be used in relation to the health benefits. One study has claimed that for Kombucha to be a healthy beverage in view of its antimicrobial activity against a range of pathogenic bacteria to promote immunity and general wellbeing, it is recommended that 33 g/L total acid, and 7 g/L acetic acid are the desired acid levels (3).
Black and green tea and white sugar are the basic ingredients, water should be boiled for 10 minutes to remove chlorine and contaminants. Tea leaves or bags are added to boiling water and allowed to infuse. After 10 minutes the leaves are removed and 50 g/L of sucrose (sugar) is added and mixed until dissolved. Once dissolved the tea preparation is left to cool. The tea is then acidified by either adding either vinegar or starter tea/ Kombucha. Then tea fungus or an old SCOBY is added, and the jar is carefully covered with a clean cloth and fastened properly. The preparation is allowed to incubate at room temperature (around 24°C or 75°F) from 5 – 15 days. During fermentation, a daughter SCOBY is formed on the tea surface. The tea fungus is removed from the surface and kept in a small volume of fermented tea. The beverage is passed through cheesecloth and stored in capped bottles at 4°C. The taste of the Kombucha changes during fermentation from a pleasant fruity sour-like lightly sparkling flavour after a few days, to a mild vinegar-like taste with prolonged incubation (5).
So why not give Kombucha a try today?