Undergraduate thesis · NCUR 2024

Aging Gracefully: Exploring the Impact of Aging on the Quantitative and Qualitative Characteristics of Pu'erh Tea

An undergraduate thesis correlating the chemistry of post-fermented pu'erh tea with blind sensory evaluations, aiming at objective, science-backed quality standards for a booming but loosely regulated market.

Read the study on ResearchGate

Elias Suskind (2024). Aging Gracefully: Exploring the Impact of Aging on the Quantitative and Qualitative Characteristics of Pu'erh Tea. National Conference on Undergraduate Research (NCUR) 2024; Babson College.

Introduction

Pu'erh tea is a culturally significant, economically valuable fermented tea from China, known for its aging process and complex flavor development. This study analyzes six pu'erh samples — three shou (ripe) and three sheng (raw) — using both chemical analysis and sensory surveys, aiming to establish objective standards for pu'erh quality and pricing in a booming but inconsistently regulated market.

Why it matters

Despite the pu'erh market's valuation at over 22 billion yuan, quality assessment remains subjective and speculative. This project correlates measurable chemical attributes — such as total polyphenol content (TPC) — with sensory evaluations, to support more transparent, science-backed pricing standards.

Background & context

Pu'erh differs from other teas because of its fermentation and aging, which lead to evolving flavors. Yet scientific analysis of pu'erh's chemical and sensory changes over time remains rare. This study controls for terroir, cultivar, and fermentation method, blending lab assays with trained-sommelier evaluations to fill a gap in the field.

Table 1 — How this study differs from prior work
Aspect	Basic tea chemistry studies	General sensory studies	This study
Tea type focus	Mostly green, black, oolong	Mixed varieties, rarely pu'erh	Exclusive focus on shou and sheng pu'erh across aging windows
Fermentation style	Rarely considered	Sometimes referenced	Isolated and analyzed independently
Control of variables	Often inconsistent	None	Controlled for terroir, cultivar, brewing
Chemical analysis	Present but not linked to flavor	Absent or minimal	Lab-tested TPC via Folin–Ciocalteu assay
Flavor profiling	Often absent	Untrained participants	Structured survey with certified sommeliers
Quantitative–qualitative link	Generalized	Flavor only	Statistical correlation between TPC and flavor/quality
Aging factor	Absent	Absent	Comparative 3-year aging analysis

Method

The project developed a hybrid testing framework blending chemical analysis and expert sensory evaluation, controlling for variables like terroir and brewing conditions to keep results accurate and repeatable.

Design goals

Standardized comparison across fermentation types and years
Minimized variability by controlling terroir, cultivar, and brewing
Accessible lab and survey techniques for replication
Objective chemical data combined with sensory feedback

Experimental system

Sample set: six pu'erh teas (three shou, three sheng) from 2021–2023
Chemical analysis: total polyphenol content via the Folin–Ciocalteu assay
Sensory survey: blind tastings by 10 certified sommeliers

Analysis pipeline

Data ingestion via CSV and pandas
Sample segmentation for per-tea analysis
TPC integration with sensory-survey results
Statistics: means, correlations, error bars, heatmaps (see Fig. 1)

Results

Chemical test (TPC)

Minimal TPC change in sheng pu'erh over three years
Year-to-year TPC fluctuations in shou pu'erh
Short-term aging showed limited impact on TPC

Chart of total polyphenol content across the six pu'erh samples and harvest years — FIG. 2 — Total polyphenol content by sample and year.

Sensory evaluation (flavor & perceived quality)

Sheng teas showed a slight increase in perceived quality over time
Strong correlation between TPC and perceived quality for shou teas (Pearson R = 0.999, p = 0.028)
Specific flavor descriptors correlated with perceived quality

Correlation matrix relating flavor descriptors to perceived quality, part 1 — FIG. 3Flavor–quality correlation matrix (I)

Correlation matrix relating flavor descriptors to perceived quality, part 2 — FIG. 4Flavor–quality correlation matrix (II)

Future work

Future research should explore longer aging periods to pin down when significant chemical and sensory changes occur. Deeper study of fermentation conditions — temperature and humidity during wodui — could optimize shou pu'erh quality. Expanding the participant pool and extending timelines will help refine the relationship between pu'erh chemotype and market valuation.

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