Simple and rapid determination of histamine in food using a new histamine dehydrogenase from Rhizobium sp.

A colorimetric enzyme assay for the quantitative analysis of histamine in food has been developed using a new histamine dehydrogenase (HDH) from Rhizobium sp. The HDH specifically catalyzes the oxidation of histamine but not other biogenic amines such as putrescine and cadaverine. The principle of our photometric assay is as follows. The HDH catalyzes the oxidative deamination of histamine in the presence of 1-methoxy PMS (electron carrier), which converts WST-8 (tetrazolium salt) to a formazan. This product is measured in the visible range at 460 nm. The correlation between the histamine level and absorbance was acceptable, ranging from 0 to 96 microM with histamine standard solutions, corresponding to 0 to 30 microM of the reaction solution (r = 1.000, CV = 1.0% or less). Assays of canned tuna (in oil and soup) and raw tuna with 45-675 micromol/kg histamine added showed good recoveries of 96-113, 98-108, and 100-106%. The histamine contents of a commercial canned tuna and fish meal containing histamine at high concentrations were determined using the new method and other reference methods (HPLC method, Association of Official Analytical Chemists official method, and two commercial enzyme immunoassay test kits). This simple and rapid enzymatic method is as reliable as the conventional methods.