Tea Science | Why is tea bitter? The truth is hidden here →

Have you ever encountered a situation where the tea you carefully brewed tasted bitter and unbearable and was difficult to dissipate?

A cup of really good tea should have a short-lived and layered bitterness, which eventually turns into sweetness and fragrance, leaving you with an endless aftertaste. However, if the bitterness of the tea soup lingers for a long time, it is likely because some links are not done well!

Today, let us explore the mystery behind the bitterness of tea from a scientific perspective.

The " natural gene " of bitter taste : substances contained in tea

The bitterness of tea soup mainly comes from the following ingredients: purines (caffeine, theobromine, theophylline, theophylline), ester-type catechins, anthocyanins, tea saponins, bitter amino acids and some flavanols. Among them, caffeine accounts for about 2%-5% of the dry weight of tea leaves and is an important contributor to the bitterness of tea soup.

The astringency mainly comes from tea polyphenols (such as catechins, phenolic acid, depsideric acid, etc.) and flavonol glycosides (such as quercetin, kaempferol, etc.), which produce an astringent feeling after combining with salivary proteins.

The "acquired factors" of bitterness: from tea garden to tea cup

** 1. Tea tree varieties and growing environment - The flavor characteristics of different types of tea are closely related to their planting varieties, picking tenderness and processing technology.

Seasonal differences : Summer tea tastes more bitter than spring tea due to the high temperature and strong sunlight, which leads to the accumulation of more polyphenols.

(AI drawing, for reference only)

2. The “key role” of production technology

Insufficient withering: Withering is a key step in tea processing. The purpose is to spread the fresh leaves to allow them to release some moisture under certain conditions, promote chemical changes in the substances contained, and thus lose the grassy smell. If the withering is not sufficient, the grassy smell will remain, and the problem of heavy astringency will easily occur during subsequent processing.

Improper withering: Withering is to destroy the activity of enzymes in fresh leaves through high temperature, inhibit the enzymatic oxidation of tea polyphenols, and emit green smell. If the withering temperature is too high or the time is insufficient, it will lead to excessive or insufficient oxidation of tea polyphenols, aggravating the astringency.

The bitterness of tea is caused by other reasons. For example, tea made from raw materials seriously damaged by pests and diseases often has a more bitter taste than normal buds and leaves, and may even have unpleasant odors such as "bitter" and "fishy", which is significantly different from the bitter taste of the tea itself.

3. The “details trap” of brewing and storage

The water temperature is too high : Boiling water can easily stimulate the extraction of bitter substances (such as caffeine and tea polyphenols). It is recommended to brew young tea (such as famous green tea) with water temperature of about 85℃.

Soaking for too long : The time it takes to brew green tea will also affect the amount of bitter substances extracted. It is recommended that green tea be brewed within 15 seconds.

Improper storage : A humid environment can easily cause tea leaves to mold and produce an unpleasant taste.

How to brew good tea that is neither bitter nor astringent?

Choose the right tea set : Use a dense white porcelain covered bowl and make the tea pour quickly.

Control the tea-to-water ratio : 1:50 is recommended for green tea, and 1:22 is recommended for oolong tea brewed in a covered bowl.

Make good use of water quality : spring water and natural water can better highlight the flavor attributes of tea.

Clever use of the "cold brewing method": timely soaking at low temperature can reduce the amount of bitter substances extracted, which is suitable for a new summer experience.

(AI drawing, for reference only)

"Technology Blessing" Scientifically Reduces Bitterness

Application of new food production technologies , such as enzyme treatment, microencapsulation technology, ultrafine grinding, subcritical water extraction, food irradiation, etc.

Agronomic measures such as selection and cultivation of appropriate tea varieties, shading treatments, pruning and fertilization.

The taste experience brought by tea is the result of the combined influence of many aspects. Through reasonable technical processes and scientific brewing methods, you can actually get a cup of tea with a balanced taste. Next time you make tea, you might as well calm down and taste it carefully to feel the delicate balance between bitterness and sweetness.

References:

[1] Ma Yuanyuan, Cao Qingqing, Gao Yizhou, Liu Yuyi, Deng Shihan, Yin Junfeng, & Xu Yongquan. (2023). Research progress on bitterness of green tea. Tea Science, 43(01), 1-16.

[2]Ye, J.-H., Ye, Y., Yin, J.-F., Jin, J., Liang, Y.-R., Liu, R.-Y., .Xu, Y.-Q. (2022). Bitterness and astringency of tea leaves and products: Formation mechanism and reducing strategies. Trends in Food Science & Technology, 123, 130-143.

[3]Xu, Y.-Q., Zhang, Y.-N., Chen, J.-X., Wang, F., Du, Q.-Z., & Yin, J.-F. (2018). Quantitative analyzes of the bitterness and astringency of catechins from green tea. Food Chemistry, 258, 16-24.

END

Source: Xu Yongquan, Research Fellow, Tea Research Institute, Chinese Academy of Agricultural Sciences, and Xu Longjie, PhD Candidate

Reviewer: Professor Liu Zhengquan, Sericulture and Tea Research Institute, Zhejiang Academy of Agricultural Sciences