Detection characteristics of a commercially available sulfite detection test (SULFITEST): problems with decreased sensitivity and false negative reactions.

Recently, a product (SULFITEST; Center Laboratories) has become available for detecting the presence of sulfiting agents in foods. Testing with SULFITEST by the indirect method (ie, holding the test strip above the food product) or the direct method (ie, touching the test strip directly on the food) was associated with false negative results in five out of nine acidic sulfite-containing foods. Quantitative studies also confirmed that low pH conditions and/or the presence of ascorbic acid caused SULFITEST results by the direct method to significantly underestimate known concentrations of sulfites. Dependence on this sulfite detection strip may lead to unrecognized ingestion of sulfiting agents, especially in acidic and/or ascorbic acid-containing foods.