Unveiling Fermentation Effects on the Functional Composition of Taiwanese Native Teas

Area of Science:

• * Agricultural Chemistry
• * Food Chemistry
• * Phytochemistry

Background:

• * Tea quality is primarily determined by processing, with limited data on Taiwanese native teas' chemical changes across manufacturing stages.
• * Cultivar, harvest, and environment influence tea composition, but processing's impact is dominant.
• * Taiwanese native teas exhibit significant diversity, necessitating a detailed chemical analysis across processing steps.

Purpose of the Study:

• * To investigate how enzymatic oxidation, rolling, and roasting affect major bioactive constituents in Taiwanese native teas.
• * To create the first stage-resolved chemical map of Taiwanese native teas.
• * To provide insights for optimizing processing to enhance functional phytochemical profiles.

Main Methods:

• * Nine representative Taiwanese teas were analyzed at four key processing stages: green tea (G), enzymatic fermentation (F), semi-finished (S), and completed tea (C).
• * Chemical components including catechins, gallic acid, caffeine, amino acids (L-theanine), POPCs, and theasinensins were quantified.
• * Effects of cultivar, fermentation intensity, withering duration, roasting, and rolling were evaluated.

Main Results:

• * Cultivar influenced green tea profiles: large-leaf types had more catechins/gallic acid; small-leaf types had more caffeine/amino acids.
• * Fermentation dramatically altered composition: catechin depletion, gallic acid formation, POPC accumulation, and theasinensin increase.
• * L-theanine decreased with prolonged withering; roasting reduced amino acids but not caffeine; rolling effects varied.

Conclusions:

• * Enzymatic oxidation is the primary driver of chemical changes during Taiwanese tea processing.
• * Processing stages significantly impact the phytochemical profile, with distinct alterations at each step.
• * This study provides a crucial chemical map for optimizing Taiwanese tea production for desired functional components.