Welcome back to our blog! This is the first of a series of blogs based on topics that we are covering at our Tea House Masterclasses. Tonight we welcomed lots of lovely people to our Bath Tea House to discuss and taste green tea. This blog covers some of the detail behind our discussions and looks to answer some commonly asked questions.
GREEN TEA OVERVIEW
Like white, oolong, and black teas, green tea is a product of the Camellia Sinensis plant. The defining characteristic of green tea is that it is made up of leaves that are prevented from oxidizing.
Strictly speaking green teas are not totally un-oxidized. This is because tea leaves begin to slowly oxidize as soon as they are picked. As actual processing may start a couple of hours after this a very slight amount will have occurred. What we therefore mean when we say 'un-oxidized' is that oxidation is not promoted in any way, but just stopped as early as possible.
Oxidation is halted by heating the leaves shortly after picking [Please note that there are some green teas that are allowed to wither for a short time before this occurs] Heating is key because it denatures the enzyme that is part of the chemical reaction of the oxidation. This process is commonly called 'kill-green' after the Mandarin 'shaqing' which means 'killing the green'. Quite simply it changes the enzyme so it doesn't work anymore. This stops the browning and means the leaf remains a green colour.
This heating can be done in a variety of ways depending on what is traditional or what tea is required. The main methods are pan firing and steaming.
Pan firing is the preferred method in China and is when the leaves are pressed or tossed in a dry, hot wok for 1-2 minutes. Examples of teas processed this way are Gunpowder and Long Jing (Dragonwell)
Steaming is more prevalent in Japan and entails the leaves moved through a rolling, steaming tunnel for 60 seconds or less. Sencha, Gyokuro and Matcha are examples of teas produced this way.
Other methods are the use of an oven, a bamboo basket over charcoal (eg. Mao Feng) and even sun-drying (rare).
ROLLING AND DRYING
After heating the leaf is rolled and dried. How this is done varies by region and producer preference. Variation in these steps can produce very different tea flavors and textures.
Rolling is undertaken by hand or machine. The leaves are simply rolled into needle-like shapes (i.e. Japanese Sencha) or balls (i.e. Gunpowder).
Finally, the tea leaves are placed in a drying room or an oven to drop their moisture content to around 3-6%. This stops any further chemical reaction and stabilizes the tea. However, oxidation can never truly be stopped, hence why tea can become stale after a period of time (usually a few years with most greens).
HEALTH & GREEN TEA
When it comes to how good tea is for you there are a myriad of claims and counter claims. This is a topic that needs a blog to itself, so in the meantime I will focus on just a few key areas of interest.
The type of processing discussed above retains the maximum amounts of polyphenols and volatile organic compounds in the processed tea. As stated this controls aroma and taste but also has health implications too.
One such compound is the antioxidant compound EGCG (epigallocatechin gallate), a type of catechin which may also hold cancer-fighting properties. EGCG is fairly simple to extract and use for pharmaceutical purposes and are continually being researched and refined [read more on green tea for health here]
Green teas have also been said to be linked with weight loss, in that they boost metabolism [read more on green tea for health here] They are also are a diuretic. We would encourage you to read more widely, check all the information available for yourself & seek expert opinion if tea & health is a particular area of interest for you.
In most instances green tea should be brewed at 80°C for 1-2 minutes; however, depending on the cut of the leaf and the level of processing, the brew time may be longer. There are some teas that require a lower temperature, such as Gyokuro, a Japanese shade grown tea.
The following references have been used in writing this article :-