Wednesday, 20 November 2013

A nice cup of tea

Women harvesting tea leaves
in Assam region of India
Tea has enjoyed a long tradition over the centuries and it really is the original herbal drink. The health benefits of tea (Camellia sinensis) are numerous and well established with a vast array of studies to support our reasons for drinking it. But of course, it remains a stalwart in the beverages world despite it being discovered by accident by a Chinese Emperor when a leaf from a nearby tree dropped into his hot water and so taken was he by its wonderful aroma, he proclaimed it good for health & well-being. From this humble beginning, tea is now enjoyed in almost every country across the globe and only just eclipsed by water as the most widely consumed drink. Ostensibly, there are 3 types of tea but they all originate from the same plant species (Camellia sinensis). It is the manner in which the leaves are prepared as well as to some extent the region in which the species is grown and cultivated that gives rise to various flavours dictated by our taste. Many tea specialists prefer the tips of the young shoots as they believe this provides the best flavours...... but as with many things to do with palate, much is dependent on taste.

On arrival at the factory, the freshly plucked leaves are laid out to wither/dry a little. This allows for some of the water to evaporate from them to the extent they can be flexible. They then undergo one of 3 processes depending on the preparation:

1. black tea
2. green tea
3. oolong tea

Black Tea
This is the dried form that is most popularly consumed and widely available. After drying, the leaves are passed through a series of oversized mincing machines which cuts, tears and curls the leaves. This process ruptures the cells (by cutting through the cell walls to release the flavours), therefore the immediately start to oxidise and quickly turn colour (initially to a coppery brown, rather like a half eaten apple would turn colour). The batch is left uncovered and the process lasts about an hour or so. In this time, the leaves undergo further oxidation so that by the time they leave the factory, the leaves are now black (hence the name).

Green Tea 
The fresh leaves of the Camellia sinensis are steamed  at very high temperature instead of dried. This means that the enzymes responsible for oxidisation are inactivated and therefore the constituents which are thought to confer the health benefits of tea (such as the polyphenols) remain intact. The polyphenols are better known as flavonoids or catechins. One of the main catechins on geen tea is a rich antioxidant called epigallocatechin-3-gattate (EGCG) which is 100 times more effective than vitamin C and 25 times more effective than vitamin E at protecting cells and genetic material) from free radical damage that is linked to many disease states. EGCG also has twice the benefits of resveratrol, a polyphenol found in red wine (and known to limit the negative effects of smoking and a fatty diet). Although many people believe green tea is better for you than black tea, there is only a marginal difference in the levels of antioxidants between the two (black tea has slightly less). The lack of oxidisation in green tea simply means that it has a more delicate flavour compared to black tea. However, many people don't like the taste of green tea preferring the raw and gutsy flavours of black tea instead. In this regard, it really is a question of taste!

Oolong Tea
Workers in a tea plantation in China
heating the tea leaves by hand

This is another variation of the preparation of the leaf. Here, the leaves are rolled and shaped into long thin strands. They are partially oxidised because after they are picked, they are allowed to dry in a similar manner to the preparation for black tea and allows them to be oxidised. However, the time for this oxidation is limited and the processed is stopped when the leaves are heated. They are shaped one last time after the heating. Many people believe that semi-oxidation produces floral note that characterise oolongs and have, over time, become synonymous with this type of tea. Some oolongs are roasted instead which produces darker aromas and flavours (many believe these flavours resemble ripe fruits, nuts, roasted grains, caramel, coffee or chocolate). The range in oxidation, shaping and roasting/heating makes oolong tea a broad category with an enormous span of flavours and aromas. Most oolongs hail from China and other countries of the far east such as Japan and Taiwan, where the hand-rolled leaves are much sought after. However, other countries such as India and Sri Lanka have now started to make oolong tea invariably on a large scale in a factory setting. Whether this is a good or bad thing remains to be seen as much of this is dictated by demand in those regions and in other parts of the world.

Tea Blending

Many of the tea specialists across the world have their own unique blends. What this means is that in different regions, the leaf of the world, Camellia sinensis acquires different chemical constituents lending itself to different flavours and textures when it is dried and roasted. The art of tea blending has been perfected over many years and many traders are passionate about their recipes and guard it as a closely kept secret. Equally, different cultures have different ways of drinking tea. It can be drunk as a brew on its own (black tea) or as many would in the West, drink it with milk. The addition of sugar also enhances the flavour. In India, tea is an incredibly popular drink, however, the classic, traditional way of making Indian tea is  to brew the leaves with hot milk and rather less water (if at all).... almost like a tea equivalent of a latte!

Health Benefits of Tea
Given the abundance and variety of biochemicals in tea, it is unsurprising that it has been closely aligned to health effects. Chemicals such as flavonoids (antioxidant properties), amino acids, vitamins, caffeine and several polysaccharides easily lend themselves to health benefits which have been extensively investigated. It has been suggested that green and black tea confer some protection against cancer though the catechins found in green tea are thought to be more effective in protecting against preventing certain obesity-related cancers such as liver and colorectal cancer. Both green tea and black teas protect against cardiovascular disease. Recent epidemiological data have been conducted to investigate the effects of green tea consumption on the incidence of human cancers. These studies suggest significant protective effects of green tea against oral, pharyngeal, oesophageal, prostate, digestive, urinary tract, pancreatic, bladder, skin, lung, colon, breast, and liver cancers, and lower risk for cancer metastasis and recurrence. A recent study found a 50% greater risk of prostate cancer amongst men who drank more than seven cups of tea per day, compared to those with moderate or lower tea intake. Preliminary lab studies show that "a wide variety of commercial teas appear to either inactivate or kill viruses,". Several types of green and black teas, regular and iced, were tested on animal tissues infected with such viruses as herpes simplex 1 and 2 and the T1 (bacterial) virus. found that "iced tea or regular tea does destroy or inactivate the [herpes] virus within a few minutes." Similar results were obtained with the T1 virus.

Green Tea vs Black Tea
There is no definite answer when it comes to deciding. Black tea has been around for centuries and continues to enjoy popularity and appeal across a wide sector of the general populations across the world. However, as with all things, much depends on individual taste and if consuming it is for a particular health benefit. The research is extensive but the conclusions suggest that what ever form tea is consumed, there is always a health benefit. On a cautionary note and paradoxically, I should warn that excessive consumption of black tea has been linked to oral cancers, mainly because of the tannins in them. However, adding milk may counteract this although there is no clinical evidence to suggest the cancer risk of excessive consumption of black tea. Further, excessive and timing of consumption may impact on iron absorption

Other Teas eg. rooibush, yerbe mate etc....??
There is now a wide selection of herbal teas but despite their popularity, the vast majority cannot do without this household essential. It has had a bit of a chequered history with regards to trade but there is no question that it remains one of the all time favourite beverages in numerous countries across the world. We all love a nice cup of tea! Enjoy.......

For more information about green tea, a good review article can be found here: 
For everything to do with tea, you can visit this site - it's all about tea and would you believe it, there is a UK Council on the subject!