How Plucking Standards and Processing Methods Reshape the Flavor of Summer Tea

Summer is the awkward season of the tea calendar. High temperatures push tea bushes into overdrive, flooding the leaves with bitter polyphenols and caffeine while draining away the amino acids and aroma precursors that make spring teas so prized. The result is a harvest that many producers treat as a liability: coarse, astringent, and hard to sell. Now a team of Chinese researchers has shown that this liability can be engineered into an asset, simply by matching how the leaves are picked to how they are processed.

The study, published in Food Science & Nutrition, took fresh summer leaves of the cultivar Fudingdabaicha from a plantation in Nayong County, Guizhou Province, harvested on June 15, 2025. The researchers collected leaves at two plucking standards, one bud with one leaf and one bud with two to three leaves, and processed each batch into four classic tea types: green, yellow, white, and black tea. That produced eight distinct teas, each following its traditional manufacturing route, from the high-temperature fixation of green tea to the long withering of white tea and the full fermentation of black tea.

A trained panel of five tea judges from the Guizhou Tea Research Institute evaluated all eight samples on a 100-point scale, weighting taste at 30 percent and appearance and aroma at 25 percent each. The verdict was consistent: teas made from the more tender one-bud-one-leaf material scored higher across the board. Green tea from tender leaves topped the table at 93.57 points, followed closely by tender-leaf black tea at 93.48, while white tea from the more mature leaves fell to 86.74. Yet the panel also found that each tea type responded differently to leaf maturity. White tea proved the most sensitive to tenderness, yellow tea the most forgiving, and the tender-leaf black tea carried floral and fruity notes that its coarser counterpart lacked.

To strip subjectivity out of the assessment, the team deployed an electronic tongue, a sensor system that quantifies bitterness, astringency, umami, and sweetness in tea infusions. The instrument confirmed what the panelists sensed and added a twist: bitterness in green and black teas rose with leaf maturity, while in yellow and white teas the opposite held true. Astringency, however, climbed steadily as leaves became less tender across all four tea types. Most strikingly, black tea processing produced the lowest bitterness values of any method, suggesting that fermentation is a powerful tool for taming the harsh edge of summer leaves.

Chemical analysis explained why. Using targeted metabolomics, the researchers quantified 19 amino acids, five catechins, and caffeine in every sample. The bitter and astringent compound load followed a clear gradient, green tea highest, then yellow, white, and black tea lowest, because fermentation and yellowing chemically transform polyphenols. The star catechin EGCG, a major driver of astringency, plummeted from 60.70 milligrams per gram in tender-leaf green tea to just 3.39 in tender-leaf black tea. Meanwhile, theanine, the amino acid behind tea’s savory sweetness, was highest in green teas, and mature leaves with tender stems actually accumulated more of it, a counterintuitive finding that challenges the assumption that tenderness always wins.

The team then applied taste activity value analysis, which compares each compound’s concentration to its taste threshold in water. Ten compounds exceeded the perceptibility threshold, including theanine, glutamic acid, aspartic acid, caffeine, and EGCG. The pattern revealed a practical rule of thumb: tender summer leaves favor white and black tea production, where their umami compounds shine, while more mature leaves with abundant stems suit green and yellow tea processing, where theanine and other umami contributors concentrate. Combining mature leaves with highly fermented processing emerged as the most effective recipe for cutting astringency.

Aroma told an equally compelling story. Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry identified a staggering 1,619 volatile metabolites across the eight teas, dominated by terpenoids and esters. Statistical modeling separated the samples cleanly into four quadrants and showed that processing method shaped the volatile profile far more powerfully than plucking standard. Green and yellow teas clustered together, as did white and black teas, and the latter pair carried significantly higher overall abundance of differential volatile metabolites, meaning they simply smelled richer.

Drilling down with relative odor activity values, the researchers flagged 126 key aroma compounds and highlighted ten superstars whose values exceeded 1,000. Dihydro-2-methyl-3(2H)-furanone, a sweet, bread-like, nutty molecule, posted the highest values of all and may be a signature aroma of summer tea. Geraniol, with its sweet floral character, peaked in white tea, while dimethyl trisulfide dominated black tea and 1-octen-3-one, redolent of mushrooms, distinguished white tea. These compounds map precisely onto the sensory descriptions the judges recorded, linking chemistry to the cup.

The broader implication is that summer tea’s reputation as a second-rate raw material is not destiny. Tender one-bud-one-leaf summer shoots remain the foundation for premium products, delivering freshness, aroma complexity, and sweetness that no processing trick can fully replicate. But for the coarser harvests that make up the bulk of the summer crop, choosing the right processing route, black tea to suppress bitterness, white or yellow tea to boost sweetness and umami, white or black tea to unlock floral and fruity aromas, can partially compensate for the raw material’s shortcomings.

For an industry in which summer leaves often go underutilized or unharvested entirely, the findings offer a roadmap for precision processing: assess the leaf, then choose the craft. The researchers note that future work should trace how key flavor compounds transform dynamically during manufacturing, potentially using isotope labeling, to turn these empirical guidelines into fully quantitative rules. For now, the message is simple and commercially potent: the same summer leaf can become a mediocre green tea or a genuinely good black one, and the difference lies in the hands of the processor.

Subject of Research: Effects of plucking standards and processing methods on the flavor chemistry of summer tea leaves

Article Title: Effects of Plucking Standards and Processing Methods on the Quality Characteristics of Summer Tea Leaves

Article References: Luo, J., Liao, S., Ding, F., Dai, Y., Liu, Z., Zhang, T., Yang, T., Li, Q., Fang, S., Li, Y., Fang, W., & Shen, Q. (2026). Effects of Plucking Standards and Processing Methods on the Quality Characteristics of Summer Tea Leaves. Food Science & Nutrition, 14(10), Article e72445. https://doi.org/10.1002/fsn3.72445

Image Credits: AI Generated

DOI: 10.1002/fsn3.72445

Keywords: summer tea, Camellia sinensis, plucking standards, tea processing, metabolomics, flavor chemistry, electronic tongue, volatile compounds, catechins, amino acids, green tea, black tea