Today i attended a Fermentation workshop hosted by Mr Tan Ding Jie, a research officer who is working at A* Star and his primary research is on Organic Synthesis and Biosynthesis of flavours. Fermentation is a biological process which is carried out by micro-organisms such as Yeast and Bacteria to transform raw materials into popular food products such as Beer, Yoghurt and Kombucha. Fermentation is a process which makes use of microbes (Yeast, Bacteria) to chemically break down substances unlike cooking which is a thermal method.
Fermentation Microbiology of Kombucha
For this workshop, we focused on the inoculated source of microbes which is refer to as SCOBY, short for symbiotic culture of bacteria and yeast which is commonly used in the production of several traditional foods and beverages such as Tempeh, Natto and Miso. There are many types of bacteria such as Lactic Acid Bacteria (LAB) and Acetic Acid Bacteria (AAB). The main bacteria that is used in the fermentation of Kombucha is Acetic Acid Bacteria (AAB), which are obligate aerobes that require oxygen to synthesise the cellulose layer. The other important component of SCOBY is Yeasts which are used in preference to Fungi & Moulds. Fungi and Moulds are avoided in the fermentation process as it is harmful to the human body. For fermentation of Kombucha, a Mixed-Culture is used of bacteria and yeast complemented with two-stage process which incorporates aerobic and anaerobic stages.
Factors that affect Fermentation
There are mainly 2 types of factors: Intrinsic and Extrinsic. Intrinsic factors are often adherent to the a certain batch of fermented product which is hard to predict. These factors include Acidity, Water activity, Nutrient content, Antimicrobial and Biological structures. Extrinsic factors would include Temperature, Relative Humidity, Gaseous Exchange and presence of microbes.
Steps of Kombucha fermentation
- Brewing of tea – This steps involves the brewing sweet tea that is used to mix with the starter culture. The tea consists of typically 1% by weight of tea, 7% by weight of sugar. The tea has to be cooled down after brewing so as to ensure that the culture will not get denatured due to high temperatures.
- Inoculate – Addition of starter culture to the brewed tea and the volume of starter to be added is around 10 – 20% by weight of total kombucha.
- Ferment – This step takes a few days (5 to 7) and it involves the aerobic fermentation of the kombucha. A material that is porous is used to cover the container containing the kombucha which allows for air to initiate the fermentation process but not any contaminants as this might lead to the formation of mould or fungi.
The picture above shows the initial appearance of the kombucha before primary fermentation. The taste of the kombucha was very sweet and it tasted like ordinary tea.
This photo was taken after 5 days and a white layer of cellulose can be seen on the surface of the tea. The tea retained its very strong aromatic flavour but it also had a a slightly effervescent texture. The layer of cellulose was hard to chew and had little flavour.
However comparing with the kombucha served in glass bottle, the one in the glass bottle had a much pleasant flavour which could be largely due to the juice that was added instead of brewed tea.
Health Benefits of Kombucha
Kombucha is traditionally a carbonated drink which is normally brewed with sugar, black or green tea and SCOBY. The drink has been promoted to be a supplement that helps to improve digestion and lower the chances of diabetes. Further research have shown that there are people who strongly advertise Kombucha as being probiotic but this has yet to be 100% scientifically proven. However one thing can be sure which is that the drink can tap into interest in the microbiome, this in turn affects the micobial communities in our gut which will affect our emotional and physical well-being. In conclusion i believe that Kmobucha has much potential into becoming a crucial component of maintaining a healthy body system in humans in the near future.