Determination of sulfite in food products by an enzyme electrode

An enzyme electrode using sulfite oxidase and a hydrogen peroxide electrode has been developed for the determination of sulfite in various food products. The enzyme was cross-linked with bovine serum albumin via glutaraldehyde and attached to the sensing area of a polarographic electrode. The electrode detected hydrogen peroxide during the oxidation of sulfite to sulfate by sulfite oxidase in the presence of oxygen as electron acceptor. The enzyme electrode exhibited a linear response up to 550 μM with a detection limit of 5 μM. The sensor was stable for a period of up to 11 h of continuous use and at least 53 days when stored in a solution of 3 M (NH₄)₂SO₄ at 4°C. The enzyme electrode was applicable for sulfite measurements in dried foods and in beverages. The results were in excellent agreement with the colorimetric technique using pararosaniline.