A patient recently gave me a kombucha starter culture (thanks Neil!) and I have just cracked open my first brew. I was surprised how delicious it was – tasting, to me, of prunes of all things!!!
In case you don’t know about kombucha, it is a fermented beverage made from sweetened tea. The photo opposite shows my simple brewing vessel – a 1.8 litre plastic lock-lid container, with the finished product in. What you can see in the top is the kombucha ‘fungus’ or SCOBY (symbiotic colony of bacteria and yeast). At first sight it looks a bit disgusting, but I can assure you it is sweet-smelling, clean and pleasant to work with. Well, OK it’s a bit slimy!
This is my recipe based on 1.5 litre:
- Make a strong sweet tea: 5 teabags organic black tea to 1.5 litres filtered water plus 100g sugar
- Leave to steep until cooled to room temperature
- Poor into sterilised container and add SCOBY which will float on top
- Fit lid to keep out airborne germs, but not too tight so as to allow gas to escape
- Place in warm room, out of direct sunlight, for 7-10 days
- When done it will taste fruity, not too sweet and lightly sparkling
- Pour off most of the brew into bottles and either:
- Drink all or some immediately, or
- Place bottles in fridge to prevent further fermentation, or
- Place bottles in a warm room to continue fermenting for a few days before transferring to the fridge
- Retain enough liquid to keep the SCOBY covered, and use this to start the next brew. Keep the lid on to prevent dust and germs getting in.
Hygiene is important throughout, as cases of poisoning have been reported where cultures become contaminated with molds including penicillin. The brewing process leads to a significant drop in pH (acidification) as the yeast convert the sugar to alcohol and the bacteria then convert the alcohol in to a range of organic acids, predominately acetic acid. With a pH typically as low as 3.5 few pathogenic organisms can survive, hence the brewing process is essentially self-sterilising. The vulnerable time is when a new brew is started as the tea will have a pH closer to 6, so make sure you don’t leave the cooling tea uncovered or lying around for too long. BTW the bacterial conversion of the alcohol means that it rarely rises above 1%, so is essentially non-alcoholic.
Here is the finished product being bottled. I have back-lit it to show off its lovely golden colour, and you can see the fizz. This batch was quite sweet to my low-carb pallet, so the bottle will be stoppered and left in a warm room so that the yeasts and bacteria can continue breaking down the sugars to create a drier brew.
Bottled kombucha will keep for quite a long time, apparently, although I expect to finish mine before the next batch is ready.
There is some evidence that Kombucha was brewed in China 2300 years ago. Like kefir – another symbiotic bacteria + yeast colony, but used to ferment milk in that case – it is not known how it came about – there is no wild equivalent. These symbiotic cultures seem to exist only alongside the human cultures that propagate them from generation to generation. The health claims for kombucha go back centuries too – it was originally a prized drink in northern China before spreading across asia, Russia and finally to Europe. Historically it was considered an elixir of eternal youth. Modern day research has so far failed to confirm this (lol)…
Although considered a probiotic the micro-organisms in Kombucha are not native to the human gut, and unlike those found in yoghurt, it is not clear if they survive the digestive process or colonise the digestive tract.
However, the organic acids produced by the organisms do have potent probiotic effects in that they appear to suppress many pathogenic bacteria and encourage beneficial species. Generally speaking, our ‘good’ gut flora flourish in an acidic environment, whilst pathogenic bacteria like E. coli are suppressed. Although much of kombucha’s probiotic benefit may be attributed simply to its acidic nature, it has been found that it has the ability to suppress a range of pathogenic bacteria (including for example, Listeria) even when the acid components are removed, ie. it contains anti-pathogenic compounds (ref). Well, you didn’t think it was going to be straight forward did you?
Personally, I wouldn’t recommend you start drinking kombucha willy-nilly in large quantities. Firstly, it contains sugar and low levels of alcohol – these can feed pathogenic flora such as candida (thrush). Secondly, you need to find out how it sits with you – sudden probiotic challenges can cause gastrointestinal upset, and exacerbation of associated symptoms. So take it slowly and start with a little at a time: A small glass every day or two is more likely to be beneficial in the long run, allowing your gut flora to adjust gradually rather than forcing sudden and dramatic bacterial population shifts.
There is some interesting research, albeit in animals, showing a range of beneficial protective effects. Only time will tell if these intriguing results translate into therapeutic uses supported by proper studies in humans.
|Diabetic rats||Improved glucose control; protective effects on pancreas, liver and kidney.|
Reduced LDL raised HDL.
|Aloulou A (2012)|
|Mice, liver protection||Improved anti-oxidant capacity compared to black tea||Bhattacharya (2011)|
|Mice, gastric ulcer healing||4 day brewed Kombucha equally effective as omeprazole||Banerjee (2010)|
|Mice, nephrotoxicity (kidney)||“Kombucha may repair damage caused by… pollutants and may be beneficial to patient suffering from renal impairment”||Gharib (2009)|
|Mice, long term Kombucha consumption||Increased life-span. Sex differentiated increase in exploration, curiosity and voluntary exercise.||Hartmann (2000)|