The Typology of Aroma and Flavor in Tea

Tea, one of the most widely consumed beverages in the world, is renowned not just for its historical and cultural significance, but also for its complex and varied sensory attributes. The aroma and flavor of tea, which are critical to its enjoyment and appreciation, are influenced by a multitude of factors, including the type of tea plant, the terroir, the processing methods, and the brewing techniques. This literature review aims to provide a comprehensive typology of the aroma and flavor in tea, synthesizing findings from various scholarly sources. By examining the diverse sensory profiles of tea, this review seeks to enhance our understanding of how different elements contribute to the overall tea experience.

1. The Chemistry of Tea Aroma and Flavor

1.1 Volatile Compounds in Tea

Volatile compounds are essential to the aroma of tea. These compounds, which evaporate quickly and are detected by the olfactory system, give each tea its distinctive scent. Research has shown that a range of compounds contribute to the aromas of different teas.

• Terpenoids like linalool and geraniol are found in green, oolong, and some high-quality black teas, imparting floral and citrus notes. The concentration of these compounds can vary significantly depending on the cultivation region. For example, teas from high-altitude regions like Darjeeling and some Japanese varieties tend to have a higher concentration of floral terpenoids.
• Aldehydes and Alcohols such as hexanal and hexenol are often associated with the fresh, green notes found in green tea. Hexanal, in particular, is responsible for the "cut grass" aroma that is characteristic of high-quality fresh green teas.

1.2 Non-Volatile Compounds

Flavor, distinct from aroma, is heavily influenced by non-volatile compounds, particularly polyphenols, amino acids, and carbohydrates.

• Catechins, the primary antioxidants in tea, are responsible for the astringency of teas, with varying levels depending on the degree of oxidation. For example, green tea, being minimally oxidized, retains higher catechin content, leading to a strong, sometimes sharp, astringency. In contrast, black tea undergoes complete oxidation, resulting in the conversion of catechins into theaflavins and thearubigins, which impart a more rounded, malty flavor.
• Amino acids like theanine are critical for balancing bitterness and imparting sweetness, particularly in green and white teas. Theanine is known for its umami qualities and is directly linked to the "savory" or "brothy" aspects of green tea.

2. Typology of Tea Aroma and Flavor

The typology section now needs to be expanded significantly, focusing on the specific aroma and flavor profiles of various tea types. Below are some detailed examples, incorporating numerical data and case studies for each tea category.

2.1 Green Tea

• Aroma Profile: Green tea generally carries fresh, vegetal, and grassy aromas. This is largely due to aldehydes like hexanal and hexenol, which contribute fresh, green notes. The steaming process used in Japanese green tea production, such as in Sencha and Matcha, preserves these aromas by preventing oxidation.
• Flavor Profile: Green tea is often described as having a smooth, slightly astringent flavor with vegetal and sometimes floral notes. The balance of catechins and amino acids (like theanine) is crucial to this taste. For instance, high-quality Gyokuro green tea, which is shade-grown and harvested early in the season, has a distinct umami flavor due to its higher amino acid content.

Case Study: In Sencha from the Uji region of Japan, a steeping temperature of 70-75°C for 1-2 minutes allows the optimal extraction of catechins and amino acids, leading to a bright, fresh flavor with a pleasant bitterness.

2.2 Black Tea

• Aroma Profile: The oxidation of black tea gives rise to complex aromas, often characterized by fruity, malty, and floral notes. For example, Darjeeling, known for its "muscatel" flavor, contains compounds like methyl salicylate, contributing to its floral, slightly sweet aroma.
• Flavor Profile: The flavor profile of black tea is typically robust and full-bodied, with bitterness balanced by sweetness. Theaflavins contribute brightness and sharpness, while thearubigins enhance the body and depth. Black teas processed using CTC (Crush, Tear, Curl) methods, like Assam tea, tend to be stronger and more astringent, whereas Orthodox-style black teas, such as Ceylon or Kenyan teas, may present lighter flavors.

Case Study: The famous Keemun black tea from Anhui, China, has a distinct floral aroma, with linalool contributing to its fragrance and its smooth, slightly smoky flavor due to the firing process.

2.3 Oolong Tea

• Aroma Profile: Oolong tea offers a broad spectrum of aromas, including floral, fruity, and creamy notes, shaped by the partial oxidation process. High-quality oolong teas like Tie Guan Yin and Red Robe often feature volatile compounds like linalool oxide (tea rose) and methyl jasmonate (jasmine). These compounds develop as the leaves are bruised and undergo multiple stages of oxidation.
• Flavor Profile: The flavor is balanced, with a mild astringency from catechins and a smooth, sometimes honey-like sweetness, depending on the degree of oxidation. Oolong teas from Taiwan, such as High Mountain Oolong, typically have a fresh, floral taste due to high-altitude growing conditions, while Wuyi Yancha (rock tea) offers a more roasted, mineral flavor.

Case Study: In Taiwanese Alishan Oolong, a brewing temperature of 90°C and a steeping time of 3-4 minutes are recommended to extract both its floral fragrance and the sweetness from amino acids like theanine.

2.4 White Tea

• Aroma Profile: White tea, due to its minimal oxidation, preserves delicate, floral, and honey-like aromas. These are primarily derived from aldehydes like cis-3-hexenol and terpenoids like linalool. The gentle drying process maintains the volatile compounds responsible for the fresh, light aromas.
• Flavor Profile: White tea is typically mild, with minimal astringency. The sweetness is often described as floral or honey-like, attributed to higher amino acid content. Silver Needle and White Peony are known for their clean, sweet, and smooth flavor profiles, which are prized for their subtlety.

Case Study: The best way to brew Bai Mu Dan (White Peony) is at around 85°C for 2-3 minutes, which allows the amino acids and catechins to release without overpowering the subtle floral and honey notes.

2.5 Pu-erh Tea

• Aroma Profile: Pu-erh tea has a unique aroma, often described as earthy, woody, and sometimes even mossy, due to its fermentation process. The presence of microbial metabolites such as geosmin and 2-methylisoborneol contribute to its earthy, musty aroma.
• Flavor Profile: The flavor is rich and smooth, with earthy and sometimes leather-like notes. Aged Pu-erh develops complexity, often with flavors of dried fruit, nuts, and even chocolate. Raw Pu-erh (Sheng) is often more bitter and astringent in its youth, while ripe Pu-erh (Shou) undergoes a fermentation process that mellows its flavor.

Case Study: Menghai Pu-erh, a famous aged Pu-erh tea, can be brewed at 95°C for 5-6 minutes, highlighting its earthy tones and rich, mellow texture.

3. Factors Influencing Tea Aroma and Flavor

The aroma and flavor of tea are influenced by several factors, including climate, soil, cultivar, cultivation methods, processing techniques, and the aging process. Each of these factors plays a role in determining the final sensory experience of the tea. Below is a more detailed exploration of these factors, with particular emphasis on the influence of aging on flavor.

3.1 Terroir

The concept of terroir refers to how the natural environment of a specific region shapes the characteristics of its tea. It encompasses climate, soil, altitude, as well as the local flora and microbial environment.

• Climate: Temperature and rainfall affect the growth rate of tea plants, their chemical composition, and ultimately their flavor. For example, tea grown in temperate climates often exhibits fresh floral and herbaceous aromas, while tea from tropical and subtropical regions may have rich fruity and woody notes. High-altitude tea regions (e.g., in Tibet, Nepal, or certain Taiwanese mountain areas) tend to produce teas with delicate flavors, a smooth texture, and a complex floral and herbaceous aroma.
• Soil: The mineral content of the soil, including its pH and nutrient composition, directly affects the chemical makeup of the tea leaves. For example, volcanic soils are rich in minerals, which help impart a unique minerality and distinctive flavor to the tea. Teas such as Assam and Da Hong Pao are renowned for their rich, complex aromas due to the unique soil conditions in which they are cultivated.
• Altitude: Higher altitudes tend to have cooler, more temperate climates, which slow the growth of tea plants. This slower growth results in more complex flavor profiles, as the plants accumulate more flavor compounds over time. For instance, Darjeeling tea from the foothills of the Himalayas is known for its floral notes and a characteristic “muscatel” flavor, while high-altitude teas often have a smoother, more refined mouthfeel, with richer floral and fruity notes.

3.2 Cultivar

The tea cultivar (or variety) is one of the most fundamental factors influencing the flavor and aroma of tea. Different cultivars have distinct chemical profiles and physiological characteristics that contribute to the final flavor.

• Camellia sinensis var. assamica: The Assam variety is used primarily for strong, robust teas such as Indian Assam tea and Chinese Pu-erh tea. These teas often have rich malt, fruit, and sometimes chocolate or honey notes due to the cultivar’s inherent characteristics.
• Camellia sinensis var. sinensis: The sinensis variety, which is typically used for more delicate teas like green tea (e.g., Longjing) and white tea (e.g., Silver Needle), tends to produce a more subtle, fresh aroma and lighter flavor profile. These teas are often characterized by floral, grassy, and lightly sweet notes.
• Hybrid Cultivars: In some regions, hybrid cultivars are used to create a richer, more complex flavor profile. For example, Japan’s green teas often use a mix of cultivars like Yabukita and Shizuoka to produce teas with more layers of flavor, balancing fresh, grassy, and slightly sweet notes.

3.3 Processing Techniques

The processing techniques used to prepare tea directly affect its aroma and flavor. How the tea is handled—its oxidation level, fermentation process, and drying methods—determines its final sensory profile.

• Green Tea Processing: In green tea production, the oxidation process is stopped quickly by methods like pan-frying or steaming, which preserves the fresh, grassy, and vegetal qualities of the tea. For example, Japanese matcha and Longjing green tea both maintain their fresh, clean flavor due to these quick processing methods.
• Oolong Tea Processing: Oolong tea undergoes partial oxidation, which allows it to maintain the freshness of green tea while also developing some of the richness of black tea. The degree of oxidation can range from lightly oxidized (producing floral and creamy notes) to heavily oxidized (with more roasted, fruity characteristics). Traditional oolongs like Tie Guan Yin have floral aromas, while heavily roasted varieties such as Da Hong Pao develop more robust, toasty flavors.
• Black Tea Processing: Black tea is fully oxidized, which results in a darker liquor and a richer flavor profile. The full oxidation allows for the development of deeper, maltier flavors. Some black teas, such as Assam or Keemun, exhibit a robust, malty flavor with fruit and spice undertones.
• Fermentation for Dark Tea: Dark teas, such as Pu-erh tea, undergo a post-fermentation process where the leaves are aged or fermented, further developing their flavor. This fermentation process can lead to the production of earthy, woody, and sometimes sweet flavors, with Pu-erh being particularly known for its “earthy” taste and the ability to improve with age.

3.4 Aging (Chenhua Process)

Aging is a unique process in tea production, particularly for Pu-erh tea, where the flavor develops and changes over time. Aging can significantly enhance the depth and complexity of the flavor, especially for certain types of tea.

• Pu-erh Tea Aging: Pu-erh tea is known for its ability to improve with age, with flavor profiles changing dramatically over time. Fresh Pu-erh is often sharp, astringent, and somewhat bitter, but over time, as the tea undergoes fermentation and oxidation, it transforms into a smoother, more complex tea with mellow, sweet, and earthy notes. Older Pu-erh, especially when stored under ideal conditions (appropriate humidity and temperature), may develop woody, musky, and sometimes even fruity or caramelized flavors. This aging process is often referred to as "mellowing" or "maturation" of the tea.
• Raw vs. Ripe Pu-erh: There are two main types of Pu-erh: raw (sheng) and ripe (shou). Raw Pu-erh is naturally aged over years, while ripe Pu-erh undergoes a rapid fermentation process to simulate aging. Both types benefit from aging, though ripe Pu-erh matures faster and tends to develop a smoother, more earthy flavor.
• Effect of Aging: Studies have shown that Pu-erh tea’s flavor improves with age, with compounds like polyphenols and catechins breaking down over time to create a smoother, less astringent cup. Pu-erh tea aged for 10 years in high-altitude areas can develop strong “chen” (aged) aromas, such as musty, woody, and sweet notes, making it a sought-after collectible tea.

Case Study: Pu-erh tea stored at high-altitude locations in Yunnan revealed that after 10 years, the flavor profile evolved from a sharp, bitter taste to a rich, mellow, and sweet profile with prominent “aged” and woody characteristics. These aged Pu-erh teas are often highly prized by tea collectors and connoisseurs.

3.5 Brewing Techniques

Brewing methods also play a crucial role in shaping the final flavor and aroma of the tea. Variations in steeping time, temperature, and water quality can all affect how a tea expresses itself.

• Water Temperature: Different types of tea require different water temperatures to best extract their flavors. For example, green teas are typically brewed at lower temperatures (70-85°C), while black teas and Pu-erh teas require higher temperatures (90-100°C) to fully release their flavor compounds.
• Steeping Time: The duration of steeping affects the extraction of compounds from the tea leaves. Too short a steeping time results in under-extraction, while too long a steeping time can lead to over-extraction, which can cause bitterness and astringency.
• Tea Utensils: The choice of tea utensils can also influence the taste. For instance, Yixing teapots (made from clay) can enhance the aroma of certain teas, while glass teapots allow for visual appreciation of the tea's color and clarity, influencing the overall sensory experience.

4. Conclusion

The typology of aroma and flavor in tea is a complex and multifaceted subject, influenced by a myriad of factors ranging from the chemical composition of the tea leaves to the specific processing and brewing techniques employed. This literature review has synthesized findings from various scholarly sources to provide a comprehensive overview of the sensory profiles of different types of tea. By understanding the intricate interplay of elements that contribute to tea's aroma and flavor, enthusiasts and researchers alike can deepen their appreciation for this ancient and beloved beverage.