Week 4 – Kombucha Workshop

Introduction

It is claimed that fermented foods possess these potential health benefits which includes: Improving immune system and reduce metabolic diseases. This makes the workshop much more exciting to learn about Kombucha – fermented tea.

Prior to the workshop, i had a vague idea of what Kombucha is but I have never tried it before. So i went on YouTube to search about it and my first impression of the drink was: This looks like a dubious drink! i guess the reason why i had that thought was because of the ingredients used but i was very fascinated to understand the purpose of the “weird” ingredient in the drink.

 

 

Hands On

We were given a jar and a bottle, the bottle contains the 10-days fermented kombucha while the jar contains the mixed-culture – SCOBY (symbiotic culture of bacteria and yeasts). Upon opening up the bottle, i can hear a light “pop” as well as a light “fizz”, like opening a can of carbonated drink. It also produced a slight hint of alcohol and vinegar scent. Question that popped to my mind: Why does the Kombucha fizz, isn’t it just a sweetened fermented tea? Later, i understood that the fizz is created by the digestion of sugar by the yeast present in the SCOBY. Similar to the beer brewing, as the yeast digest the sugar in the tea, releasing carbon dioxide and effervescent is observed.

 

Afterwards, we were asked to fill half of the jar with brewed black tea.

As the tea has not been sweeten, we had to add a tablet of carbonation drops that is usually used in beer making. It just looks like a hard mint candy and it comprises of sugar and glucose. After adding the carbonation drop, it started to fizz and dissolve in the mixture.

 

Factors Affecting Fermentation Process

There are many factors affecting how our Kombucha is going to turn out. Here are some of the variables:

• Temperature – Every 10 degrees increase in temperature doubles the rate of fermentation
• PH – When the fermentation process begins, the Acetic acid bacteria (AAB) present in the SCOBY converts sugar to acetic acid, lowering the PH of the Kombucha. If our goal is to achieve a sweeter Kombucha, we can try to increase the PH, if we want a tarter Kombucha, we can let lengthen the fermentation process to decrease the PH. This can be tested by using a PH strip for the ideal PH level.
• Nutrient Content
• Humidity
• Presence of antimicrobial substances
• Composition of gas 

Fermentation Process

The SCOBY used in the fermentation process is an obligate aerobe which requires oxygen to grow. Through cellular expiration, the SCOBY needs oxygen to metabolise the sugar in the tea mixture. To allow oxygen to enter the jar while preventing ants or insects from crawling into the jar, i placed few layers of tissues over the opening of the jar and secured it with rubber bands. I left the jar away from direct sunlight and stored it in room temperature.

Over the course of fermenting, i observed a layer of “Whitish Foam” floating on the top of the Kombucha. The foam is called the Cellulose Pellicle and it is formed on the air-liquid barrier. It is actually the SCOBY ! Interestingly, the cellulose produced by the bacteria is similar to that of a plant cellulose! After a week of fermentation, the layer thickens and has a waxy texture to it. I was worried that it is a sign that my Kombucha turned bad and fungi have grown in the culture. But i went back to trace the notes in the workshop that unless i spot some “furry white/greenish” mould or yeast growing on the surface, i would then have to dispose the whole culture T_T! Thankfully, all is good.

Some precautionary measures to take before we start on the fermentation is that we must always have good hygiene practices – using clean tools and hands to prepare the culture. As my Kombucha is getting a little too fizzy, i experimented by putting the jar into the fridge as every 10 degrees increase in temperature doubles the speed of fermentation. Indeed, the Kombucha mixture became less fizzy and it didn’t pop as loud as the bottled Kombucha that is left to ferment at room temperature.

There is strong pungent smell as the Kombucha ferments, similar to vinegar yet reminding me of how a bottle of apple cider would taste like. Took a sip of the Kombucha, it tasted a little weird yet interesting. It has a sweet note and is very carbonated. I have not tried to mix in some fruit juice into the mixture but would try out some time later and i would definitely compare it to a store-bought one.

How cool to find out that with just a few simple ingredients – Tea, Sugar, Water and SCOBY, we can actually create something out of it and it is delicious! Another cool fact is that the SCOBY formed on the top layer can be removed and reuse for my next bottle of Kombucha fermentation. All in all, the workshop was very enriching and eye-opening, I would be keen in learning how to ferment kimchi by myself in the near future.