The diverse and ever-changing scents of tea are one of the main motivators for many new tea enthusiasts to get started, and a source of enjoyment for seasoned tea connoisseurs. For example, green teas have a “roasted chestnut” or “fried bean” aroma, while black teas tend towards a “sweet fruit” or “flower Honey” scent. The variety of aromas in Pu'er tea is even richer, with raw Pu'er offering Lotus, orchid, and fruity scents, as well as apricot aroma, while ripe Pu'er has glutinous rice, jujube, woody notes, and more. Many of these aromas can overlap.
Where do all these aromas come from? Why do so many of them only approximate rather than perfectly match the descriptions they're given? In this article, Lu Li will guide tea enthusiasts through the different layers of tea aromas and where the various types of Pu'er tea aromas originate.
Sources of Pu'er Tea Aromas
In earlier times, Taiwanese tea expert Deng Shihai summarized four types of Pu'er tea aromas: camphor, lotus, orchid, and green (fresh) aromas. Later, the industry continued to summarize the rules of changes in Pu'er tea aromas, adding more descriptive terms that contributed to the development of the Pu'er tea aroma system.
Typically, freshly produced Pu'er tea often still retains a hint of “green grass” scent. Some blended teas may have an unfused aroma, which might be somewhat mixed, but after proper aging for a certain period, these scents gradually transform into a fresh fragrance.
In subsequent transformations, Pu'er teas made from different materials and stored under varying conditions exhibit a myriad of aromas. The general progression of raw Pu'er tea aromas can be summarized as: fresh → floral → honey-like → aged (medicinal).
The aroma of ripe Pu'er tea is primarily the result of microbial activity, and it already has a noticeable aged scent after pile fermentation, though it usually also carries a heavier fermentation smell (such as heap odor) and a small amount of early-stage aroma. Therefore, the aroma changes in ripe Pu'er tea can be generally described as the aged scent becoming purer and individual aromas blending together over time.
Firstly, regarding the aging aroma, different tea regions produce different aged aromas when stored long-term, although they can all be grouped under the broad category of “aged” aromas.
Secondly, the aroma changes in raw Pu'er tea do not involve a leap from fresh to floral and then to honey-like scents, but rather a gradual process where each aroma blends with the next and transitions slowly.
This is because most of the various types of aromas in Pu'er tea come from enzymatic and microbial fermentation, which produce a large number of flavor compounds. These flavor compounds themselves contain diverse tastes, allowing us to perceive flavors reminiscent of certain fruits and plants, such as fruity-floral, hawthorn, and apricot aromas, among others.
In fact, over 700 flavor compounds have been identified in tea, which can be categorized into 15 major groups: alcohols, ketones, acids, aldehydes, esters, lactones, phenols, hydrocarbons, peroxides, Sulfur compounds, pyridines, pyrazines, quinolines, aromatic amines, and others.
However, although there are many types of flavor compounds in Pu'er tea, the quantities of individual compounds are small. All the aromatic substances combined make up approximately 0.02% of the dry weight of the tea leaves, and only dozens of these play a decisive role in determining the aroma.
This results in relatively weak and fleeting aromas in Pu'er tea that don't precisely match the specific fragrances of particular fruits or plants, a phenomenon also seen in wine and coffee tasting.
Therefore, when describing the tasting notes of a particular Pu'er tea, we often use multiple similar aromas and even scenes with specific atmospheres, which is part of the enjoyment of Pu'er tea tasting. Below, we'll briefly introduce some typical aromas and their chemical mechanisms.
Green Grass Scent, Fresh Aroma: Geraniol
The green grass scent and fresh aroma mainly come from geraniol, an aromatic compound that smells like fresh grass and has a relatively low boiling point. It is the primary volatile odor in fresh leaves, accounting for about 60% of total volatile substances.
Tea enthusiasts who have experienced the fixation process will have noticed a strong green grass scent, which is actually the geraniol volatilizing in the air. During the Wilting, rolling, and especially fixation processes, heat and enzymatic action cause most of the geraniol to volatilize.
The remaining geraniol then undergoes chemical reactions during post-fermentation, forming trans-geraniol, which creates a fresh aroma. This scent is delicate, not overpowering, yet natural and harmonious, making it comfortable. It is commonly found in young Pu'er teas and sun-dried rough teas, evoking images of deep forests and vast grasslands, etc.
Floral, Fruity Aromas: Aromatic Alcohols, Carotenoids, etc.
Floral, fruity, and fruity-floral aromas are the “big three” in Pu'er tea aromas, commonly found across different materials but with variations due to the content and reactions of aromatic alcohols, amino acids, carotenoids, and other substances.
Aromatic alcohols refer to a group of alcohols with various types and possess apple, rose, and narcissus-like scents. They are present in fresh leaves and various tea types, mostly formed during the rolling and fermentation stages. Higher-grade teas typically contain more aromatic alcohols.
Amino acids and carotenoids also participate in reactions, profoundly affecting the aroma of Pu'er tea. Certain amino acids, such as glutamic acid, alanine, and phenylalanine, have floral scents, while threonine has a wine-like aroma.
During the tea-making process, some amino acids combine with oxidized polyphenols to form aldehyde compounds with fruity and spice-like tones. When carotenoids undergo oxidation and degradation, they produce many substances with intense floral scents.
Orchid, Lily Aromas: Linalool
Floral aromas are one of the most common types in raw Pu'er tea, with an exceptionally rich variety. Among these, some refreshing floral scents, like orchid, lily, and others, are particularly sought after. The source of these aromas is linalool.
Linalool, also known as linalyl alcohol, is a high-boiling-point aromatic compound that is most abundant in large-leafed tea varieties in Yunnan. Within the same region, tea trees grown at higher altitudes, cooler temperatures, and slower growth rates tend to have higher levels of linalool in their leaves.
The above tea aromas are evident in many tea types, and in the next article, Lu Li will continue to introduce several unique Pu'er tea aromas and explore the origin of the Ginseng-like aroma in aged Pu'er teas.