title: Judgment of pure fermented soy sauce by fluorescence resonance energy transfer of OPA-tryptophan adduct.
abstract: Tryptophan was detected with a flow-injection manifold after reacting with mM order of fluorogenic o-phthalaldehyde (OPA)/thiol reagent (pH 10.0) in the carrier stream (0.63 mL/min). Based on the intra-molecular fluorescence resonance energy transfer of OPA-tryptophan adduct, the difference in fluorescence intensity obtained at 280 and 300 nm excitation was used to detect tryptophan content with satisfactory precision (CV<6.5% for concentration higher than 0.5 μM), linearity (0.1-10 μM, R(2)=0.9893) and sensitivity (≈10 nM). Since tryptophan will decompose during manufacturing non-fermented soy sauce by acid-hydrolysis procedure, the method was used to discriminate pure fermented soy sauces, adulterated soy sauces and chemical soy sauces in less than 5 min. The ratio of tryptophan to total amino acid content served as the index for the judgment, and the results were validated by capillary electrophoresis.
authors.affiliation: Department of Bio-Industrial Mechatronics Engineering, College of Bio-Resources and Agriculture, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: You-Syuan
authors.initials: YS
authors.lastname: Gao
authors.affiliation: Department of Bio-Industrial Mechatronics Engineering, College of Bio-Resources and Agriculture, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Bo-Chuan
authors.initials: BC
authors.lastname: Hsieh
authors.affiliation: Department of Bio-Industrial Mechatronics Engineering, College of Bio-Resources and Agriculture, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Tzong-Jih
authors.initials: TJ
authors.lastname: Cheng
authors.affiliation: Department of Bio-Industrial Mechatronics Engineering, College of Bio-Resources and Agriculture, National Taiwan University, Taipei 10617, Taiwan. Electronic address: rlcchen@ntu.edu.tw.
authors.forename: Richie L C
authors.initials: RL
authors.lastname: Chen
mesh_terms: D000596:Amino Acids; D005285:Fermentation; D017022:Flow Injection Analysis; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D045730:Soy Foods / Q000032:analysis*; D014364:Tryptophan / Q000737:chemistry*; D009764:o-Phthalaldehyde / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D009764:o-Phthalaldehyde; D014364:Tryptophan
keywords: Flow-injection analysis (FIA); Fluorescence resonance energy transfer (FRET); Soy sauce; Tryptophan; o-Phthalaldehyde (OPA)