Identification of Marker Compounds for the Detection of Anthraquinone-Based Reactive Dyes in Foods

The detection of reactive dyes in food matrices is crucial for food safety and compliance with regulations, especially since the use of such in food products is not approved. This study investigates the potential of using tin(II)chloride and laccase to cleave anthraquinone reactive dyes and to detect their characteristic degradation products as markers for the presence of dye in food. Nine reactive blue anthraquinone dyes and one green anthraquinone dye were cleaved using tin(II)chloride and laccase. Reactions with reactive dyes bound to maize starch were also carried out to evaluate the suitability of these methods for detecting matrix-bound dyes. Model food matrices, including gummy candy, hard candy, and maize chips, were spiked with the reactive dyes, and the presence of degradation products was analysed using LC-ESI-MS/MS. Two common cleavage products were formed from each sample, namely 1,4-diaminoanthrahydroquinone-2-sulphonic acid (DAHS) and 1-aminoanthraquinone-2-sulphonic acid (AAS). In all examined cases, at least one of the characteristic cleavage products could be detected. Laccase showed lower effectiveness with matrix-bound dyes, whereas treatment with acidic tin(II)chloride was effective even in complex food matrices. These findings suggest that the analysis of cleavage products could be a valuable tool for the detection of reactive dyes in food matrices.