Studies on the Fate/Loss (?) of Sulfathiazole in Concentrated Carbohydrate (Honey) Solutions

Abstract

Sulfathiazole (ST) contamination of honey has recently become a major concern for regulatory agencies. Although numerous chemical methods to test for ST in honey have been developed, none of these methods has examined the binding of ST to reducing carbohydrate (Maillard reaction) in honey. While ST treated at pH 3.6 and 80°C in water was completely stable over a thirty day period, ST treated under similar conditions in the presence of excess reducing carbohydrate (D-glucose and D-fructose) resulted in greater than 50% loss of free sulfathiazole in only 65 hours. Free ST also disappeared at slower rates from reducing carbohydrate solutions held at room temperature. ST bound to carbohydrate had different chromatographic properties from free ST and did not react with Bratton-Marshall reageant. Problems associated with present rapid detection methods for free ST in honey were investigated and a modified procedure to detect free ST to levels of 125 ppb developed. Since all chemical methods for ST analysis in honey did not detect carbohydrate bound ST, these methods not only underestimated the original ST contamination of honey but also could underestimate the antibiotic contamination of honey if bound ST acted as a reservoir for free ST and/or bound ST still maintained antibiotic activity.