Improving the Tea Withering Process Using Ethylene or UV-C
Emma R. Collings, M. Carmen Alamar, Maria Bogaerts Márquez, Sofia Kourmpetli, Zoltán Kevei, Andrew J. Thompson, Fady Mohareb, Leon A. Terry
Abstract
High Resolution Image Download MS PowerPoint Slide Using a combination of biochemical, transcriptomic, and physiological analyses, we elucidated the mechanisms of physical and chemical withering of tea shoots subjected to UV-C and ethylene treatments. UV-C irradiation (15 kJ m –2 ) initiated oxidation of catechins into theaflavins, increasing theaflavin-3-monogallate and theaflavin digallate by 5- and 13.2–4.4-fold, respectively, at the end of withering. Concomitantly, a rapid change to brown/red, an increase in electrolyte leakage, and the upregulation of peroxidases ( viz. Px2, Px4, and Px6 ) and polyphenol oxidases ( PPO-1 ) occurred. Exogenous ethylene significantly increased the metabolic rate (40%) and moisture loss (30%) compared to control during simulated withering (12 h at 25 °C) and upregulated transcripts associated with responses to dehydration and abiotic stress, such as those in the ethylene signaling pathway ( viz. EIN4-like, EIN3-FBox1, and ERFs ). Incorporating ethylene during withering could shorten the tea manufacturing process, while UV-C could enhance the accumulation of flavor-related compounds.