Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system
Resource
Food Chemistry 118 (3): 876-881
Journal
Food Chemistry
Journal Volume
118
Journal Issue
3
Pages
876-881
Date Issued
2010
Author(s)
Abstract
A novel fluorometric flow-injection analytical system is utilised to determine tannin and total amino acid levels in tea for taste assessment of astringency and umami, respectively. The quenching effect on fluorescence of 3-aminophthalate was employed to determine tannin levels, and the fluorogenic reaction of o-phthalaldehyde (OPA) was applied to quantify amino acid content. Both reactions were measured by a single fluorescence sensing system with same excitation and emission wavelengths (340/425 nm). A three-way valve was introduced to switch reagents for sequential determination of tannin and amino acids levels. Parameters of operational conditions were optimised, and the effect of tannic acid on OPA-based amino acid determination was also investigated. The linear dynamic ranges for tannic acid and theanine are 50-250 and 0.1-1.0 μg mL-1 (CV < 5%, n = 3), respectively. Each sample throughout was 20 samples h-1. This system was also applied to quantitatively assess the quality of partially fermented teas. © 2009 Elsevier Ltd. All rights reserved.
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