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Exploration of factors to enhance aromatic quality in green tea

Sun, Litao (2022) Exploration of factors to enhance aromatic quality in green tea. PhD thesis, Murdoch University.

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Tea flavor comprises two groups of chemical compounds that contribute to taste (non-volatile compounds in water) and aroma (volatile organic compounds, VOCs). Aromatic substances are the most crucial components of tea quality and stimulating the consumers’ sense of smell. My PhD research focused on understanding the factors which can impact or improve aromatic substances in tea leaves from the pre-harvest application of organic manure to post-harvest treatments. This study explored the interaction between the tea plant–microbiome and the mechanism of how the application of organic fertilizer change the metabolites of the tea plant, particularly VOCs changes, and furthermore, to provide a theoretical reference for the control of green tea aromatic quality through analysis of real-time aromatic characteristics during tea brewing.

The results showed that the application of organic manure in tea plantations can trigger significant changes in the metabolic pathways of amino acids, sugars and fatty acids in tea leaves related to aroma. The application of organic manure in tea plantations can significantly change the composition and abundance of rhizosphere-associated bacterial communities. Organic acids and fatty acids affected by the application of organic manure were potential regulators mediating the plant-bacteria interaction in the rhizosphere soil. Proteiniphilum, Fermentimonas, Pseudomonas, Saccharimonadales, Gaiellales, Acidobacteriales and Gaiellales were the potential genera that can regulate relative contents of organic and fatty acids. Esters, aldehydes, alcohols, fatty acids and alkaloids were the predominant volatile groups in tea infusions. The variation of the same volatiles between the tea infusion and the corresponding headspace tended to balance during the tea brewing process. Two to three minutes was identified as the best duration for the tea brewing that maximized the abundance of aromatic chemicals in the headspace released from the tea infusions.

This study is the first-time providing evidence from direct manipulation of the soil microbiome or certain specific compounds that can offer to improve tea plant development and performance. In addition, a theory and modern technology-based reference method was provided for simulation of green tea sensory test using analysis of the real-time aromatic characteristics.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Agricultural Sciences
Supervisor(s): Ren, Yonglin, Agarwal, Manjree and Ding, Zhaotang
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