Preliminary exploration of the loss of free Methylselenocysteine during selenium-rich tea processing

Methylselenocysteine (SeMC), the primary organic selenium in tea, enhances human nutrition through its bioavailability and bioactivity (e.g. antioxidant activity). This study investigated SeMC stability during tea processing: high-temperature fixation caused 48.11 % SeMC loss (vs. 25.54 % when rolling at 25 °C), following first-order kinetics (Ea = 65.58kJ/mol, air). Nitrogen protection reduced degradation to <10 % at 150 °C. We first report that 29.19 % of oxidised SeMC (SeMCO) regenerates to SeMC at 25 °C, challenging the assumed irreversibility of selenium oxidation. Catalase (≥200 U/mg) synergized with nitrogen to inhibit oxidation, enabling 1) shortened thermal exposure, 2) nitrogen blanketing, and 3) enzymatic control. These results provide practical solutions to preserve selenium functionality during tea processing, thus advancing selenium-rich food production.