Determination of Free Amino Acids in Cheese by Flow Injection Analysis with an Enzymic Reactor and Chemiluminescence Detector

Abstract

ABSTRACTThe substrate is degraded enzymatically by L‐amino acid oxidase immobilized on controlled porosity glass. The hydrogen peroxide generated by the reaction is determined by chemiluminescence with an alkaline reagent containing luminol and hexacyanoferrate (III). The log‐log calibration graphs for L‐leucine were rectilinear from 0.025 mM to 1.0 mM (R = 0.9998). The coefficients of variation (rds) for n = 10 were 1.4% and 0.3% for 0.1 mM and 0.8 mM of L‐leucine, respectively. The sample throughout was 40 h‐1. The concentration of free amino acids in cheese samples was 14 to 50 mg L‐leu/g product. The enzyme reactor showed good stability over 4‐months.