Ok, so you are someone that loves a good mug of loose leaf tea. Be it Green, Black, or some form of herbal tea. You have your favourite type and you know just how to brew it to get the taste you love but you have started to wonder what is involved in getting this amazing leaf from the field to your mug ready to be lovingly steeped.
I remember asking myself that question, followed by a considerable amount of time going down the google rabbit hole trying to find my answers. I then realised that other tea lovers might be interested in learning a little bit more about the world of tea processing, rather than leave you to find all the information for yourself, I decided to place everything I have learned from reading books and searching the internet into a single place. I really hope you enjoy it and that it answers all the questions you might have when it comes to tea processing.
The 10 steps to processing tea leaves
When processing tea there are 10 steps that need to be followed. We have listed all the steps below. Each type of tea has its own specific processing requirements that dictate the style of tea the producer is going for along with any specific taste they might be targeting. All styles of tea, however, will go through the first 2 steps.
Harvesting
This stage of the process is where the leaves are plucked from the plant itself. When harvesting the farmer will take great care to ensure that only the bud and the main leaves are picked from the Camellia Sinensis plant.
Tea is normally harvested by hand, it is done this way to prevent damage to the leaves. If the leaves are damaged this can start the oxidation process early, damage to the leaves will also reduce the overall grade of the tea. Machines can be used and some of the more modern machines can be used quite successfully when it comes to the preservation of the leaves but it is generally avoided when it comes to high quality tea as the producers do not want to risk the damage to the leaves.
Tea plants are normally harvested twice a year once in early spring and again in early summer. The first harvest of the year is commonly known as the “first slush” and as you might have already guessed the second harvest, the “second flush”
First Flush relates to the leaves that have been harvested at the start of the year, this harvest is believed to be of better quality for most types of tea as the leaves have had more time to grow. It is not the case however for all teas, for example, second flush Darjeeling is thought to be superior to first flush. The first flush is normally harvested in march.
Second flush relates to the second harvest in the year, the leaves from this harvest have not had as long to grow when compared to the harvest earlier in the year. However, they do grow faster due to the extra sunlight. This harvest normally takes place in late May into June.
In some areas, further, harvesting is done throughout the year. The time of year tea is harvested, impacts the way the tea is processed along with the way it tastes. The subject of harvesting deserves more detail than I can give it in this article so watch this space if you want to know more.
Wilting/Withering
This step is in place, to begin removing moisture from the leaves and normally takes around 14 hours. It is common for the leaves to be picked during the day and then left to wilt overnight. The moisture in the leaves will drop roughly 35% during this process. While the moisture is slowly reducing the leaves will also go through some slight oxidation.
Different situations can call for different levels in this process, you can have what is known as a soft wilt and the complete opposite, a hard wilt. Both of these are used to impact the flavour profile to reach the desired outcome.
This is done for a couple of reasons -
- Promotes the breakdown of proteins into amino acids
- Increases the availability of freed caffeine
- Impacts the flavour of the tea
Disruption
When the leaves get to this stage they need to go through some level of disruption. To put it plainly, the leaves are damaged to aid in aswell as speed up the oxidation process. To do this the leaves are torn or bruised, normally by either tossing the leaves in a tray or tumbling them in a basket.
Machinery can be used for this stage in the form of kneading, rolling, tossing, and crushing. This presents some benefits when it comes to processing large amounts of leaves and can be much faster than the more traditional methods.
Many producers and also consumers believe that this stage also has an impact on the taste of the tea which suggests that each method used can have a different impact on the end result.
Oxidation
Leaves are left in a controlled environment to allow oxidation. As the leaves oxidize they begin to darken. Sometimes this is aided by agitation using machinery.
Chlorophyll in the leaves is enzymatically broken down and tannins are released or transformed, the tannins are what create the interesting textures and flavours in the tea.
The oxidation process will be stopped based on the type of tea required. This is done by taking into account not only the amount of time the leaves have been breaking down but also the temperatures and the weather conditions. All this has an effect on the final taste.
Typical levels of oxidation in relation to the type of tea -
Light Oolong tea - 5-40% Oxidation
Dark Oolong tea - 60-70% Oxidation
Black tea - 100% Oxidation
What does the oxidation process affect when it comes to the end result?
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Taste
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Armoa
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Colour
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Strength
If the oxidation process ends too soon the taste of the tea will be effected along with the colour. You can also do the opposite and have fully Oxidized tea, like any of the black tea’s.
This is not to be mistaken for post-fermentation, that is something else entirely.
What is fermentation when it comes to tea leaves?
The tea of this description is known as post-fermentation tea. It has undergone microbial fermentation from months potentially up to multiple years.
Leaves are exposed to humidity and oxygen during a process called endo-oxidation.
What sort of effect does fermentation have on the tea?
- Changes the smell
- Mellows the taste
- Reduces astringency
- Reduces bitterness
- Improves mouth feel
- Better after taste
- May benefit health
The fermentation is carried out by moulds, originally thought to be Aspergillus niger but this has been challenged with other analysis pointing towards Aspergillus luchuensis.
China is the main producer of this style of tea but you can find it in other areas like Korea and Japan. In the UK you will mostly see this style of tea in the form of a cake or a ball.
Fixation
In this step of the process, the tea leaves are “fixed” once the leaves are within the producers’ parameters for the type of tea being produced. The “fixing” of the leaves is done to stop any further oxidation. If the leaves were left to continue oxidizing the taste profile would be affected and the tea would not taste the way the producer was targeting.
This is done using heat, we touched on this earlier in a previous step. When the leaves are heated, the oxidative enzymes are deactivated therefore preventing the oxidation from continuing. It is also used to remove unwanted scents from the tea.
This step is traditionally done by panning the leaves in a wok or steaming them however more recently a machine called a panning drum is used as it can process larger quantities in a shorter amount of time.
Sweltering
This step of the process is used exclusively for yellow tea. The leaves will be stored in some form of container to keep them warm but also damp. This changes the colour of the leaves from green to yellow.
The ideal temperature for this step in the process is around 37℃, the leaves will be left in these conditions for between 6 & 8 hours resulting in a brisk and mellow taste.
Rolling/Shaping
In this step, the leaves are rolled, into strips. This can be done in the more traditional way, by hand but also using a rolling machine. The rolling of the leaves removes some of the essential oils, along with some of the sap still in the leaves improving the overall taste of the tea.
Tea consumption is rather high across the globe. We don’t do too bad ourselves here in the UK either. As I am sure you can imagine, this means a lot of leaves need to be rolled to keep us all going while sat on the sofa with a brew. The traditional method of hand rolling has limitations when compared to the use of rolling machines. A rolling machine is capable of processing 25kg of leaves in a single operation, so it goes without saying, rolling machines are pretty common.
The rolling machines are made up of a set of grooved rollers, pressed against each other. This only leaves space for the leaves to pass through the small groves, in turn rolling the leaves into strips while at the same time squeezing out the unwanted oils and sap.
Once the leaves have been rolled either by hand or by machine they are then ready to either be left as they are or made into other shapes. The shapes you are likely to see when it comes to tea are -
- Pellets
- Balls/pearls
- Bricks
- Cones
- Half spheres
Drying
The drying stage is used to prepare the tea for sale and can be done in a variety of different ways. The leaves can either be dried through panning, leaving out in the sun, air drying or baking.
Baking is the most common method for this stage, though care has to be taken as the leaves can suffer from overbaking. Overbaked leaves are not suitable for sale as the flavour profile of the tea will be greatly effected.
The impact this step has on flavour is considerable across all types of tea. It does however affect green tea the most, it is a very important part of the process.
Ageing
This step of the process is reserved for post-fermentation teas, some of which require aging to get to their full potential. This ageing process can be anything from a couple of months running upto years.
If you look at green tea Puerh as an example of how the aging process affects the way the tea will taste. Prior to aging, the green Puerh has a bitter and harsh flavour profile before it has been cured into a post-fermentation tea. The curing results in giving the tea a sweet and mellow taste.
Oolong tea is another example of a tea that benefits well from some curing time but this is normally done over charcoal.
It would be hard to do this topic justice within this article, it should really have an article dedicated to all the intricacies involved. Maybe one for the future, I guess you can let me know if it’s something you want to know more about in the comments.
Sorting
This process is pretty self explanatory, as a consumer, all you really want, when buying loose leaf tea is the leaves. You don’t want to open your package and find half of it is full of seeds and stems.
The flavour comes from the leaves, anything else is just taking up space that could have been more leaves. It goes without saying then, that all the stems and seeds need removing. This step does exactly that.
This process is commonly done with machinery especially when it comes to black tea. Some machines are even clever enough to separate the leaves based on the colour to ensure grading is accurate. The more traditional way to work through this process is by hand sifting and picking out the unwanted bits.
How the process dictates each style of tea
When you are buying tea, you will need to pick from a selection of different types. These types are distinguished by the level of oxidation that they have been exposed to. Each tea type has a specific set of parameters in relation to oxidation and we will cover them below
Black tea
Black tea is one of, if not the most commonly consumed styles of tea in the uk. With the uk population consuming 71400 metric tons in 2022, and the 2023 estimations to be almost 76000 metric tons. If your drinking an everyday tea in the form of a teabag from any of the major brands then there is a good chance that it’s black tea of some description. These everyday teas are most commonly made with a blend of Assam and Ceylon “leaves”. I use the word leaves loosely when it comes to tea bags, if you want to know a little more about why check out this post.
The withering process for black tea will remove upto 75% of the moisture content in the leaves before moving on to the disruption step of the process where the leaves will be either bruised or torn. This disruption of the leaves, promotes the oxidation process and speeds it up.
The oxidation process for black tea will last anywhere from 45 minutes to 3 hours. Throughout this process the humidity of the area will be high and the temperature will be controlled to keep it between 20℃ and 30℃.
When talking about black tea processing you need to understand that there is more than one way to process it. Orthodox processed black tea is the traditional way of processing the tea leaves but you can also get black tea that has been processed using the CTC (Cut, tear, curl) method.
When black tea has been processed using traditional orthodox methods it will follow the same grading system as the teas above. This system is known as the pekoe system. Black tea that has been procesed using the CTC method will normally not be graded.
Green tea
Green tea is wonderful, there are so many different options when it comes to green tea, all of which have been through the steps above with varying parameters but share a common theme.
When processing green tea it does not spend very long in the oxidation step, the aim is to keep the leaves as fresh as possible. This is done by heating the leaves very early on after harvesting. If the leaves have been farmed in Japan then the preferred method for this step is to steam the leaves. In China, however, leaves are roasted or cooked in hot pans.
The leaves can then be left to dry separately or rolled. If you’re opting for the rolled leaves it is likely that you’re getting what is commonly known as gunpowder green tea. This is a slow process, you tend to find that because of this it is reserved to the higher quality pekoes.
The entire process for preparing green tea takes no longer than 2 days after the leaves have been harvested. Because of this, the bulk of the chemical composition of the leaves can be preserved. This is part of the reason why green tea has so many positive benefits when consumed.
If you are looking for a rich complex taste then you are better opting for a green tea that has been roasted. If you want a bright vivid green coloured tea then you need to be looking for leaves that have been steamed. When starting out with green tea, expect to put some work into finding your preferred taste.
The steeping process can also be a little more involved with a considerable amount of experimentation. There are different methods of brewing with multiple types of “teapot” all resulting in slightly different flavour profiles.
Oolong tea
The term Oolong, is used to cover any tea would be considered as semi-oxidised. This style of tea is commonplace in the south of China with the most common method of preparation is known as gongfu style, which translates to “making tea with skill”. If you frequent any tea related content online you will undoubtedly come across this Fujian method of brewing. It is heavily used by those of us that enjoy high quality tea, as it gives you a lot of control.
This brewing style differs greatly from the western style of brewing tea. Smaller vessels are used along with a much higher leaf to water ratio and shorter steeping times but more of them. A tea pet is a common part of the Fujian brewing method too. All this combined is what is known as a tea ceremony.
The whole process from withering to drying lasts around 3 days for Oolong tea. Oolong can vary massively, with the producers putting a lot of effort into cultivating strains of the Camellia Sinensis plant to achieve very specific tastes. This tea can be anywhere from 5% - 70% of the way through the oxidation process, so I am sure you can imagine with a range like that you can find many different flavour profiles.
With that said, many producers try and keep the oxidation as low as possible when it comes to Oolong as it is thought that the shorter the oxidation process the better. Some consumers however can find that they suffer from stomach issues when drinking some of the Oolong teas that are at the very bottom end of this scale.
White tea
White tea is processed using young leaves, these leaves go through the oxidation process but this is limited through a very specific withering process. The preferred method for withering is done through drying the leaves naturally with sunlight and then baking them.
The optimal conditions for withering white tea are very specific, with humidity playing a considerable part. Producers aim for 30℃@65% relative humidity over the span of 26 hours.
When producing other styles of tea, the leaves will go through some form of disruption but when producing white tea, the leaves are protected form bruising/tearing. This is done to retain as many of the white hairs as possible on the leaves.
Yellow tea
Yellow tea is processed in the same way as green tea the only difference being, it is stacked and gently heated in humid conditions. The humid conditions are what bring out the yellow colour in the leaves with the ideal temperature for this being around 37℃, this is what gives the leaves their distinctive flavour profile.
Fermented tea
Fermented teas undergo a second oxidation after the fixation of the initial oxidation process. These teas are commonly known as Pu-erh, Liubao and Liu’an. As we mentioned earlier, this is done sometimes over the space of years and involves microbial fermentation as mentioned earlier when going through the oxidation phase in step 5.
This style of tea is a niche all of its own, so I will cover this section of the tea industry in a separate article.
So, that pretty much sums up the process your wonderful leaves have to go through before they get to you ready for brewing. Crazy right, who knew it was such a vast and variable process.
Just goes to show, it’s not just us tea drinkers that like to experiment with different timings and temperatures to get it exactly how we like it.
Wrapping it up
So you should, by now have a good understanding of not only why the teas you enjoy drinking are the way they are but also how the taste and colour are achieved through the use of different steps, temperatures, and time variants. Not to mention the fact that some of the producers also put a great deal of effort into cultivating specific strains of the Camellia Sinensis plant to achieve some of the more specialised teas that you can get your hands on.
Hopefully, I have been able to answer some of the questions you might have had with regard to the processing of tea, if you think I have missed anything or have something that you believe is worth adding please let us know, either by email on info@bertysbrews.co.uk or through the comments section.
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