Talking of Tea: Part Two
Continuing our series on the art of tea, in this instalment we turn our attention to different methods of processing and look at how these methods produce characteristic taste profiles.
Similarly to coffee, different processing methods produce different taste profiles. All tea leaves arrive at the factory in the same condition; it is the method of processing the leaves that produces the unique characteristics of each tea. Processing is carried out at the earliest opportunity after harvest and nearly always on the estate.
The process of tea manufacture involves inducing physical and/or chemical changes in the leaf. Typically there are four stages of processing; withering, rolling, fermentation and firing. The extent of processing will be dependent on the type of tea desired; for example traditional black tea will go through all four stages of processing whereas white tea will only go through two stages.
The withering stage involves spreading newly plucked leaves over trays and directing fresh or heated air over them for up to 24 hours. This weakens the cell structure of the leaves so they can be easily rolled. They will lose approx. 40 percent of their weight during this stage.
After withering the leaves are rolled either by hand or machine. This process bruises and crushes the leaves, breaking the cell structure, releasing essential oils and enzymes and flavours locked inside. Rolling can take up to one hour. During this process, whole leaf tea receives its characteristic twist.
The next stage of the manufacture process is fermentation. The process of fermentation oxidises the leaves and changes their chemistry. The extent to which this process is carried out will depend on the type of finished tea desired. In white tea manufacture, no fermentation takes place, the leaves are hand rolled and dried in the sun or baked. In green tea manufacture, fermentation is prevented, the leaves are rolled and the characteristics of the natural leaf are mostly preserved. In oolong tea manufacture the leaves are fermented for a short time until they are partially oxidised. In black tea manufacture the leaves are fully fermented. When undertaking the fermenting process, the leaves are layered in a special automatic turning oxidising machine or spread thinly on a glass or tile floor and left for several hours until they turn a bright copper colour. The full process of oxidation, in a humid atmosphere, can take hours. This oxidation is largely responsible for the flavour, strength, body and colour of the finished tea.
The final stage of tea manufacture is firing. This process involves exposing the leaves to a blast of hot, dry air. Firing stops the fermentation process and prepares the tea for storage and transportation.
There are two main types of processing, Orthodox and Cut Tear Curl (CTC). Both of these methods encompasses the four stages discussed above. The traditional orthodox method produces whole leaf and broken leaf grade tea. The CTC method is an efficient mechanized process and produces only broken leaf grades. Broadly speaking, orthodox manufactured tea will typically demand a higher price due to the labour intensive process used during production. CTC manufactured tea is cheaper to produce and consequently used primarily in tea bags as it produces a coloury liquor with strong taste.
In the next post we will focus on tea grading – unscrambling the SFTGFOP riddle! If you missed the first instalment of our tea series catch up here.