What is Black tea, everything you should know
It is said that tea is the most popular beverage, next to water. The two most common teas in the market are Black Tea and Green Tea. The fundamental difference between black tea and green tea is in the processing of the two. While the processing of black tea gives full rein to the enzyme Polyphenoloxidase, allowing the enzyme to ferment or oxidize the substrate- the Polyphenols present in the tea leaf, the first step in the processing of green tea is the total inactivation of this enzyme by heat, so that the polyphenols remain intact. In China the polyphenoloxidase inactivation is carried out by 'pan heating', the freshly picked green tea leaf being heated in a hot pan. In Japan the inactivation is by steaming. Apart from the fermented Black tea and the unfermented Green tea, there is also a third group of semi-fermented teas, called Oolong tea. Of these the most widely consumed are the black teas, followed by the green teas. Oolong tea is most popular in Taiwan. All these teas are known to have health benefits.
At one time it was thought that green tea had more health benefits than black tea. However, it has now been found that the product Theanine found in black tea, produced during fermentation, has more health benefits than the unoxidiced polyphenols in the green leaf. Presently it is known that both black and green tea have the same health benefits.
Black Tea Manufacture
A good leaf standard of tender 2-3 leaves and bud is considered ideal for black tea manufacture. Quantitative comparisons of some of the important constituents, viz. polyphenoloxidase, polyphenols, amino acids and caffeine, for black tea, are concentrated in the bud and the first two leaves and less in mature leaves. Hence the importance of a good leaf standard.
The first step in the manufacture of black tea is Withereing. It was thought at one time that withering is for the sole purpose of moisture loss and concentration of the substrate- polyphenols and the enzyme- polyphenoloxidase, to facilitate fermentation. The rate of chemical reactions being directly proportional to the concentration of the reactants. Now it is known that several biochemical changes take place during withering, most of which is completed in 6-10 hrs. The prolonging of the period of wither beyond this period, is mainly for the loss of moisture. During withering, there is the breakdown of proteins to amino acids. These amino acids play a vital role in the development of colour, flavour and the bouquet of tea liquors. At the same time the breakdown of the green Chlorophyll molecule to black Phaeophytins, by the loss of its magnesium atom and the conversion of same to brown Phaeophorbides by the enzyme Chlorophyllase commences during withering (completed during fermentation and drying of the made tea). Chlorophyllase is mostly present in coarse leaf, hence the importance of a good leaf standard. In terms of the appearance of made tea The colour of the made tea plays a role in the appearance of the made tea; black being preferred to brown tea. Also, there will be an increase in caffeine, conversion of carbohydrates to sugar, oxidation of carotenoids to yield products of great importance for flavour (playing a decisive role in the valuation of a tea) and there is an increase in permeability of cell membranes, which would help fermentation.
The next step in manufacture is to precondition fermentation, by breaking down the epidermal cells to release the enzyme polyphenoloxidase and breaking down the cells in the palisade layer below, to release the unoxidiced polyphenols (Catehins). There is also a mild rolling of the broken withered leaf during Preconditioning, to give a twist to the leaf particles, of importance in made tea appearance.
Next follows Rolling, which is the break down proper of the withered leaf into particles of different size, of importance in the grading of tea. In Orthodox Manufacture, common in Sri Lanka, orthodox rollers are employed, which helps a reduced break down of the leaf particles, when compared with CTC manufacture, employing CTC rollers, used to get a much reduced particle size, which increases colour and strength, at the expense of flavour present in Orthodox tea. Ceylon tea is now further reduced in particle size using the Rotorvane, which retains the flavour while reducing the particle size.
The rolled leaf is next spread in fermenting beds, 2 inches or so high, for Fermentation. The principal reaction which occur during fermentation is the oxidation of polyphenols by the enzyme polyphenoloxidase in the presence of oxygen (air).
The Theaflavins add flavour and health benefits to the made tea, they get polymerized to Thearubigins with the continuation of fermentation. giving colour and strength to the made tea.
Next the fermented tea (dhool) is Fired (dried), Graded and Packeted. Ceylon Black Tea is considered the "best in class" Orthodox Tea in the world, well known for its Flavour.
Black Tea is well known for its Health Benefits. It is a pleasant source of water, a minimum volume of which is needed for health and well-being. The antioxidant properties of tea are well established. Tea is comparable to red wine, as a pleasant source of antioxidants (of course red wine is more expensive!). It is known to reduce coronary heart disease, The first indication of the protective effect of a high consumption of black tea on ischaemic heart disease was given by the Boston Collaborative Surveillance Programme in 1972. Tea controls Diabetes. It is used in the treatment of Cancer, accelerating the immune systems in the body. 'Tea And Health' by Dr. W.D.Moder and Dr. A.M.T, Amarakoon of the Tea Research Institute of Sri Lanka, gives the health benefits of tea in great detail.