Extract from our book :
Tales of the Tea Trade
One Oolong tea worth a special mention due to its unusual processing is GABA tea. This relatively new type of tea was first produced in 1987 in Japan by Dr Tsushida Tojiro while researching food preservation. GABA stands for gamma-aminobutyric acid, an amino acid that occurs naturally in the human body (as well as the tea plant) and is the main inhibitory neurotransmitter found in the nervous system.
The tea involves a unique processing method instead of the traditional ‘kill- green’ stage, which increases the levels of GABA in the tea – hence the name. Processing starts as normal and requires high-grade leaves, as these have the higher amount of natural glutamic acid needed for conversion into GABA . The tea plants are often shaded for about 10 days prior to being picked, as this has been found to increase levels of glutamic acid even further. The fresh leaf is placed in a stainless steel container and one of two methods is used. The first involves pumping in nitrogen to remove the oxygen and then exposing the tea to this anaerobic, nitrogen-rich atmosphere and a temperature of over 40°C for around 8 hours. The second involves sucking the air out to create a vacuum and leaving the leaves in this state for around 24 hours. These methods both result in the conversion of the glutamic acid in the leaves into GABA. This process can be performed in all types of tea, leading to GABA green, GABA oolong, and so on.
The benefits of the increased level of GABA are said to be mostly health related. In addition to all the healthy bene ts of tea drinking, it’s claimed by many that increased GABA decreases stress and anxiety, helps to improve memory and alertness, aids in weight loss and acts as a natural sleep aid.
With all health claims we like to err on the cautious side, and some experts disagree with these claims. Doctors at New York University’s Langone Medical Center have observed that ‘when GABA is taken orally, GABA levels in the brain do not increase, presumably because the substance itself cannot pass the blood-brain barrier and enter the central nervous system’.
What cannot be argued is that GABA teas have a distinctly different aroma and flavour profile from other teas made in the same style. The process raises the level of catechins, called gallate esters, in the leaves, which are responsible for the aroma of many fruits, spices and herbs. These unique GABA aromas and avours are what we think will help continue its success in the long term, rather than the reputed health benefits.
A Taiwanese producer, Mr Yu, makes one of the GABA teas we sell at Comins. At the time of writing we are selling a Spring GABA oolong from Mr Yu. We are also introducing a very unique GABA green tea using leaves from two family farms in Nantou. A combination of two cultivars and a unique processing that brings something very interesting in the cup. One for the explorers out there!