Environmental Effects on Tea Quality
Abstract: Plant-based products are highly complex samples that contain hundreds of volatile secondary metabolites. These natural products are often used as flavoring agents in foods, beverages, and pharmaceuticals and as odorants in cleaning supply, personal care and other consumer products. Plant secondary metabolites play a vial and important role in plant defense and are thought to be response ... read morefor sensory and nutritional quality of the plant. The composition of plant volatile extracts is affected by plant species, geographical origin, cultivar, plant organ, maturity, and environmental factors, making identification of individual constituents challenging. The complex nature of plant-based products makes it difficult to identify all of the constituents by gas chromatography/mass spectrometry (GC/MS) alone. The work described herein employs automated sequential, multidimensional gas chromatography/mass spectrometry (GC-GC/MS) to obtain a matrix-specific retention time/index and mass spectrometry database. Once the targeted metabolite database is produced, it can be used with spectral deconvolution and mass spectral subtraction of routine GC/MS data to reveal untargeted metabolites, providing an efficient, reliable, and unambiguous means to identify all constituents. Specifically, metabolites were used to track how climate variations affected teas harvested in Yunnan and Fujian Province in China. Striking differences in concentration were observed in response to elevational, seasonal, and yearly differences. In addition, a field-practical volatile sample collection method was developed to measure plant response to environmental stress in situ.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Chemistry.
Advisor: Albert Robbat Jr..
Committee: Charles Mace, Samuel Kounaves, and Christopher LaFratta.
Keywords: Analytical chemistry, Food science, and Climate change.read less