Changes in antioxidant, non‐volatile and volatile contents of mulberry leaf green tea prepared using different fixation methods

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BACKGROUND: Fixation technology plays a crucial role in the processing of mulberry leaf green tea (MLGT); however, the effect of different fixation treatments on tea quality remains unexplored. The present study comprehensively investigates the antioxidant capacity, key non-volatile compounds (free amino acids, tea polyphenols, soluble sugars, total flavonoids, and alkaloids), and volatile profile of MLGT produced with four fixation techniques, namely hot-air roller, microwave, blanching, and steam. RESULTS: The key non-volatile compounds and antioxidant capacity (DPPH and FRAP evaluation systems) were highest in the microwave-processed MLGT sample. A total of 1025 volatile compounds were identified using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry, and aldehydes were the most predominant aromatic compounds in MLGT. The total content of aromatic compounds (peak area) was highest in the hot-air roller processed MLGT sample. Notably, 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one, (E)-1-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)-2-buten-1-one, 5-(Z)-4-heptenal, (E,Z)-2,6-nonadienal, and 1-hepten-3-one were identified as key odor-active compounds (rOAV ≥ 100), which contributed floral, soybean, fatty, and green notes. These compounds were least abundant in the blanched MLGT sample. In addition, 481 differential volatiles were identified as contributing to the aromatic profile based on partial least squares discriminant analysis with variable importance in projection > 1 and P < 0.05. Flavor annotation from these differential compounds revealed that the microwave-processed MLGT sample contained the highest levels of desirable aromas (e.g., sweet, fruity, nutty, woody, and herbal), while the blanched tea sample had the lowest levels of unpleasant notes (e.g., green, spicy, and fatty). CONCLUSION: Microwave and blanching are recommended fixation methods for MLGT processing. This study provides a theoretical basis for optimizing fixation technologies to enhance the flavor quality and health-related properties of MLGT. © 2026 Society of Chemical Industry.

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