Improvement of Alkaline Hydrolysis Treatment for the Determination of Residual Sulfite in Liquid Foods by a Microbial Sensor Method

For the determination of residual sulfite in liquid foods by a microbial sensor method, the conditions for decomposition of combined sulfite into free form by sodium hydroxide and antioxidant were examined. The microbial sensor method was applicable to the determination of sulfite in beer by being made flat. The optimum antioxidant and the concentration was determined to be L-cysteine monohydrochloride and 4(w/v)%, respectively. Under the optimum conditions, the recovery of added sulfite from 7 kinds of liquid foods was 90.0 to 99.4%. For the determination of total sulfite, the reproducibility of this method was better than that of the modified Rankine's titration method. These results indicated that the microbial sensor method by alkaline hydrolysis treatment was applicable to the determination of residual sulfite in liquid foods.