Determination of histamine content in vegetable juices by using direct and competitive immunosensors

An Optical Waveguide Lightmode Spectroscopy (OWLS)-based immunosensor was developed for selective and sensitive determination of histamine content in fermented vegetable juices. The conjugate of the antigen (histamine-bovine serum albumin 10 µg mL⁻¹) was attached on the amino modified sensor surface with glutaraldehyde. During the measurement standard solutions or samples were mixed with antibodies of appropriate concentration (1:1000), the mixture was incubated for 1 minute and injected into the OWLS system. The amount of antibodies bound to immobilised antigen conjugates was inversely proportional to the histamine content. Relative substrate specificity of the antibody was studied, and besides histamine, only putrescine, cadaverine and agmatine were found to give slight sensor responses. Fermented vegetable juice samples treated with different microorganisms were measured in 1000-fold dilution, and analytical data were compared to those measured by HPLC. It was concluded that the method is suitable for the sensitive and selective determination of histamine content.