Yat's Tea



Use of Wild Yeast in Beverages
This post concerns fermentation using yeast, sugar and tea to produce a beverage. Yeast plays an important role in the development of taste of many fermented products such as beer, wines and some types of food. Yeast naturally breaks down sugars and other chemical compounds that have a discernible influence on taste. Traditionally, brewers of wine and beer have been highly selective when deciding which yeast they use.

Here in Hong Kong, there are not many chose of commercial grape wine and beer yeasts as in USA and Europe, the most common product is a ball of yeast used in the production of rice wine. Instead of always having the same taste, due to repeatedly using the only commercial yeast on the market, it is interesting and adventurous to capture some wild yeast. As many brewers know, capturing and using wild yeast is not a simple task but the potential benefits of getting a unique and appealing tea beverage makes using wild yeast worth the effort.


Where can Wild Yeast be Found
Research tells us that yeast occurs naturally in some fruits and in the air, which surrounds us. When environmental conditions are correct wild yeast multiply on their own and convert sugars into alcohol. As an enthusiast of tea beverages I want to see if dry tea leaves have any wild yeast.

When tea leaves are freshly picked, there should be yeast present but processing of fresh tea leaves into dry leaves may be too harsh for any yeast to survive. That means our exercise is to determine if any wild yeast survived the processing from fresh tea leaf to dry tea leaf. To make that determination I selected assorted dried tea leaves for an experiment. I also chose two fruits for comparison.


Preparation and Capture of Wild Yeast
A solution is prepared that is 20 percent white sugar. Jars to be used in the experiment are pasteurized to eliminate any contaminants. The tea leaves selected for this part of the experiment are placed in the jars with the sugar solution. The jars are closed but the lid is loose, in order to allow the air to enter the jars and each jar is shaken once or twice daily to supply it with fresh air. The room temperature is maintained between 16 and 20 degrees Celsius.

ExperimentResults
Of five tea leaves used in the experiment three contain yeast. As a result of different runs of the experiment, there are now five different yeast cultures. Two are from fruits and three are from dried tea leaves. It is unknown, at this time, if these five yeast strains are the same. It is likely the majority of them will be the same but if they aredifferent, how will five different yeast cultures affect the taste of a beverage?

Tea:

Organic White Down Silver Needle (Fuding) -> Yeast

Premium White Peony – > Yeast

Green Pu-erh (Shui Huang Jin)  -> Yeast, Mold

Black Pu-erh -> Mold

Wuyi Oolong (Heavily Roasted) – > No visually sign of mold and yeast

Fruit:

Kiwi-> Yeast

Mandarine-> Yeast

Experimental Observations

Total lenght of the experimet was 8 days. Two days after the experiment started, the White Down Silver Needle dried tea leaves and fruits showed signs of yeast. First there was a pungent sweet smell and signs of bubbling as a result of the chemical reaction where sugar and yeast combine and result in the formation of alcohol and Co2 ( the bubbles). Three days later the White Peony, followed by the Green Pue-rh dried tea leaves followed suit. The rest of my dried tea leaf and sugar concoctions showed no signs of reactions indicating the formation of alcohol or Co2. Some dried tea leaf and sugar combinations that were non reactive for alcohol did have mold under the jar lid.


Hypothesis Based on Experimental Observations

There may be a good reason the dried White Tea leaves worked best in the experiment. White Down Silver Needle and White Peony Tea are both teas that have a minimal amount of processing from fresh picked tea leaf to dry tea leaf. In fact, the process they undergo is totally natural, wilting and drying in the sun. Apparently, the natural wild yeast present in their environment remains somewhat active.

I consider my experiment a success. The wild yeast obtained from White Tea is strong and active, as noted by the fierce bubbling action. My next experiment will be to make alcohol with this white tea wild yeast. In the end, obtaining wild yeast was much easier than I thought. If you have access to dried White Tea leaves perhaps, you can try to duplicate my experiment. It would be interesting to get information on the results that you get.

White-Down-Silver-Needle-Day1

White Down SIlver Needle Yeast Culture day8

Sugar Solution with Yeast from White Down Silver Needle

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Next experiment, Tea Wine?