Saturday, November 24, 2012

Tea Processing and Brewing

A recent trip to a tea shop made me realize that I no longer have a firm grasp on all of the distinctions between tea processing methods, due to my focus on coffee. Obviously this is unacceptable.

I will limit my discussion here to the five most common types of tea, leaving aside such rarities as yellow tea. I will also avoid discussion of non-tea 'tea', i.e., steeped plant matter that is often called tea but not made from Camellia sinensis (e.g., herbal blends, rooibos, honeybush, yerba mate). The types of tea I'll discuss are: black, green, oolong, and white. All four types are made from the same species of plant, which has two main varieties. Most Chinese, Taiwanese, and Japanese teas are made from the variety Camellia sinensis sinensis, which has a low yield but a smooth, sweet flavor. Most Indian and Ceylon (Sri Lankan) teas are made from Camellia sinensis assamica, or a hybrid of the two varieties. Assamica is higher yielding and stronger in flavor.


Black tea has the longest tradition of consumption in the western world. The major producers of black tea are India (Assam, Darjeeling, Nilgiri), Sri Lanka (Ceylon), and China (Keemun, Yunnan, Lapsang Souchong). Black tea processing consists of four stages. After picking, the fresh tea leaves are left out in the sun to dry (though not completely), a process known as withering which lasts 8-24 hours. Then the leaves are sent through heavy metal rollers which bruise the leaves, rupturing the cell walls of the tea and exposing its innards to the air. The bruised leaves are left until fully oxidized. The leaves are then fired in a heated drying chamber, which removes the remaining moisture. Ready to drink.

Green tea production and consumption is centered in China and Japan. Some famous Chinese green teas include Long Jin (Dragon Well), Huang Shan Mao Feng, and Bi Luo Chun. Sencha dominates Japanese tea production. Green tea differs from black tea in that green tea is unoxidized. After picking, the leaves are immediately exposed to heat in order to deactivate oxidative enzymes. In China, this is typically accomplished through pan frying or baking, while the Japanese use steam. After de-enzyming, the leaves are rolled into the desired shape, often by hand. The shape of a green tea leaf may identify the variety of tea; Bi Luo Chun, for instance, is rolled into a distinctive spiral. Finally, the shaped leaves are fired to remove the remaining moisture.

Oolong's flavor lies between green and black tea, because oolongs are partially oxidized, with levels of oxidation ranging from 8%-85%. Oolong is mainly produced in China and Taiwan (AKA Formosa). Some famous dark oolongs include Da Hong Pao (Red Robe) and Dongfang Meiren (Oriental Beauty). Some famous green oolongs include Tieguanyin (Iron Goddess) and Dongding. Oolong processing is quite involved. Oolong leaves are allowed to grow larger and more mature before picking, which makes for slower oxidation, allowing the processor a greater degree of control. After picking, the leaves are withered for no more than a few hours. They are then carefully and gently bruised through hand-tossing in baskets. The bruised leaves are left until the desired level of oxidation is achieved, then pan-fried to halt the oxidation process. The leaves are rolled into shape and then fired. Many oolongs are then roasted over low heat for hours or even days, which adds roast flavor, further reduces moisture and improves the tea's longevity.

White tea is produced mainly in China. There are three traditional Chinese varieties: Baihao Yinzhen (Silver Needle), Bai Mudan (White Peony), and Shou Mei, listed here in order of price and prestige. White tea is processed in much the same way that natural processed coffee is: it's picked and then left in the sun until dry (mechanical driers are also sometimes used). A modicum of oxidation occurs during drying. The result is a mellow, sweet, and nutty cup of tea.

Pu-erh is a unique form of tea produced in the Chinese province of Yunnan from assamica plants. Pu-erh comes in two forms: raw and ripe. Raw pu-erh is essentially a green tea that is sun-dried rather than kilned after rolling, resulting in a modicum of oxidation. It tends to taste pretty rough when fresh, so it's usually aged for long periods of time before consumption, which slowly darkens the tea and smooths out the flavor, as well as adding complex, earthy aromas. Ripe pu-erh is a more recent invention, intended to mimic the flavor of aged raw pu-erh. Ripe pu-erh is made from raw pu-erh which is moistened and piled in heaps, then monitored and turned regularly for 6 - 12 months. The damp, warm environment increases microbial activity. Raw and ripe pu-erh are available in both loose leaf and compressed form; pressed pu-erh ages more gracefully.


Different types of tea require different brewing techniques. Though all tea should be steeped in hot water, the temperature of the water, the ratio of tea to water, and the length of the steep all vary by the type of tea. To a certain extent brewing practices are culture-dependent—in China, for example, even black tea is generally steeped for a shorter period of time with more tea (compared to Western practice)—so it's worth experimenting with tea/water ratios and steep times, but these traditional methods are a good starting point.

Black tea should be steeped in water of at least 200˚ for about four minutes, though you may want to steep longer if you wish to add milk. About 2 tsp of tea per 8 oz of water should be used; use more if the tea leaves are particularly large, less if they're broken or small. You can steep black tea up to two times.

Green tea should be steeped in ~180˚F water for 2-3 minutes. About 3g / 150ml (2 tsp / 5 oz) should be used. Green tea yields 2-4 infusions.

White tea should also be steeped at ~180˚F, but the steep should be closer to five minutes. About 3g / 150ml (2 tsp / 5 oz) should be used. White tea also yields 2-4 infusions.

Because the processing of pu-erh breaks down most of its tannins, it's near impossible to over-steep. However, it is generally prepared gongfu (see below). In any case, it should be given a quick rinse with hot water before brewing, which removes any impurities on the tea.

Oolong tea can be brewed in the same manner as green tea, but traditionally brewing oolong involves a more complex protocol, known as gongfucha. Water between 180˚ and 200˚F should be used, depending on how oxidized the oolong is. The bare bones of gongfucha are as follows:

1. Pre-heat the tea equipment with hot water.
2. Fill small teapot (3-8 oz) 1/4 – 1/3 full of tea, or 5 – 8 grams / 4 oz. Traditionally, an Yixing clay pot dedicated to brewing oolong is used.
3. Rinse the tea leaves: fill the teapot halfway with hot water, then discard immediately.
4. Fill the teapot full of hot water.
5. Steep for 30 seconds. Pour into a serving vessel, then into several small cups. (This isn't the kind of thing you do alone.) 5 - 8 infusions should be performed in close succession. Increase steep time by ~10 seconds for each subsequent infusion.


Thursday, November 22, 2012

Coffee Processing Revisited

One of the first aspects of coffee to catch my attention was coffee processing, the steps involved in extracting the coffee seed (bean) from the fruit. I noticed that all of the coffees that I liked most at Peet's were either natural processed or wet-hulled. As I started drinking lighter roasts, my tastes turned to classically washed coffees. So clearly my original conception that the flavor of a coffee is just a result of how the coffee was grown and roasted was misguided.

However, I didn't have a good understanding of what the specific differences between different processing methods were, in large part due to ignorance about the steps involved and the plethora of synonymous terms used for processing methods. So I did some research and made a chart. Since then, I've discovered some finer-grained distinctions in processing methods, so at this point I think the information will probably be better presented in prose. All this information is available elsewhere, but I haven't found anywhere online where all of the details that I'm interested in have been collected in a concise and readable manner. If you're already familiar with the basics of coffee processing, you can skip this next bit.

Understanding the differences between processing methods requires understanding the steps involved in processing, which in turn requires understanding the anatomy of the coffee fruit. It starts out looking like this:

The outer skin of the coffee fruit is known as the pulp. The gooey flesh of the fruit inside the pulp is called mucilage. Inside the mucilage is a membrane surrounding the seed, known as parchment.  What follows is a brief description of the five stages involved in coffee processing: pulping, fermentation, washing, drying, and hulling. Note that not all processing methods utilize all of these stages, as I will discuss below.

The pulping stage involves removing the skin of the fruit, which is done mechanically. Then comes fermentation, when the de-pulped fruit, the gooey mess you see below, is let sit to allow microbes to break down the mucilage.

After fermentation, more water is used to wash off the loosened mucilage, and the result is parchment coffee, which is just the coffee seed and the innermost layer of parchment. The parchment coffee is then dried. (Dried parchment coffee shown below.)

Once dried, the parchment coffee is sent through hulling machines to remove the parchment, and the green coffee is ready to ship to the roaster.

1. Wet Process AKA Washed Coffee:

The vast majority of arabica coffee is wet processed. What characterizes all wet processing methods is the use of water to remove the mucilage. The most significant differences between different wet processing methods are: length of fermentation; whether water is added during fermentation (dry fermentation vs. wet fermentation); and moisture content at hulling. Wet processing is the most consistent method of producing defect-free coffee.

1.1 Latin American method

The coffee is pulped, then dry fermented for up to 24 hours. Water is introduced to wash off the loosened mucilage, followed by drying and hulling.

1.2 Kenyan method

The coffee is pulped, then dry fermented for up to 3 days. Water is used to wash the coffee, which is then soaked for 24 hours. The parchment coffee is then dried and hulled.

1.3 Ethiopian method

The coffee is pulped, then wet fermented for up to 3 days. More water is used to wash the coffee, which is then dried and hulled.

1.4 Wet-hulling (Indonesian method)

The coffee is pulped, then dry fermented overnight (usually; my sources conflict on this). The coffee is hand-washed, followed by a short period of drying. The parchment coffee is hulled before it has fully dried (i.e., more than 11% moisture remains), leaving the green coffee exposed to the environment while still moist and hence bacteria-friendly. This process results in increased body, lower acidity, and a distinctly rustic, earthy character.

1.5 Machine-assisted wet process

Some farms use elaborate machines called mechanical demucilagers to pulp and wash the coffees all at once, without a distinct fermentation stage. These can also be used to only partially remove the mucilage, resulting in a coffee that rests somewhere between washed and pulped natural. This type of coffee is sometimes called honey processed, though that term is also used to describe pulped naturals, a dry processing method.

A note on semi-washed. This term is the cause of much confusion in discussions of coffee processing. It is used to refer to either wet-hulled coffee or coffee that has been partially demucilaged mechanically, two distinct processes that produce dramatically different coffees. I prefer to avoid the term altogether.

2. Dry Process:

Dry processed coffees are produced without removing the mucilage prior to drying.

2.1 Natural Process

The coffee is not pulped after picking; rather, it is immediately laid out to dry in the sun, a stage which lasts for 2-4 weeks. When the coffee has fully dried, it is sent through a hulling machine, which removes the pulp, mucilage, and parchment all at once. Like wet-hulling, this process results in increased body and lower acidity, but generally has a bit less earthiness, greater complexity and can result in intense dark berry and wine-like flavors.

Most natural processed arabica comes from Yemen, Ethiopia, and Brazil. Brazilian natural and pulped natural coffee forms the base of most classic espresso blends. There is an important distinction between the way that Brazilian and Ethiopian natural processed coffee is generally harvested. In Ethiopia, the coffee is hand-picked over a period of time to ensure that all the coffee is at the same level of ripeness when picking, while in Brazil, farmers generally wait until the coffee is extremely ripe and then mechanically strip-pick the trees, which means that many of the coffee cherries have already begun to dry on the branches. Brazilian naturals tend to be nutty and mild, while Ethiopian naturals tend to be powerfully fruity.

2.2 Pulped Natural AKA Honey Process

The coffee is pulped after picking. When the coffee is dry, a hulling machine removes the mucilage and parchment. The flavor of pulped natural coffee rests between washed and natural processed coffee. Pulped natural coffee is produced around the world but is especially associated with Brazil.

Drying Methods

All dry processed coffee and most high-quality wet-processed coffee is sun-dried. Confusingly, sun-dried is sometimes used as a synonym for natural processed. African farmers usually dry their coffee on raised beds, while Latin American coffees are generally dried on cement patios.

An interview with Peter Giuliano which can be found on James Hoffman's blog (main source)