A colorimetric sensing platform for azodicarbonamide detection in flour based on MnO2 nanosheets oxidative system

Azodicarbonamide (ADA), as a dough conditioner food additive in flour, can be turned into toxic biurea and semicarbazide after high temperature processing. Hence, the using of ADA in food material should be strictly controlled, and the detection of ADA is very important for consumers’ safety and health. Herein, a simple and fast colorimetric strategy has been developed for ADA detection based on the MnO2 nanosheets-3,3′,5,5′-tetramethylbenzidine (TMB)-glutathione (GSH) as oxidative sensing system (MnO2-TMB-GSH). Since the ADA can selectively react with GSH via oxidizing the sulfydryl (-SH) group of GSH to disulfide bond (S-S), which makes GSH unable to reduce MnO2 nanosheets and restore its oxidase-like activity. The absorbance changes of the TMB solution depended on ADA content. The MnO2-TMB-GSH colorimetric platform can detect the ADA with a linear range of 10 μmol L−1 (11.6 ppm) to 400 μmol L−1 (464 ppm), and the limit of detection (LOD) is 3.3 μmol L−1 (3.51 ppm). Some potential interferences in real sample were tested and did not affect the MnO2-TMB-GSH colorimetric platform for ADA detection. Furthermore, the sensing platform was applied for detecting ADA in real flour sample with a recovery of 96%–105% (RSD < 5%). This colorimetric method can effectively and rapidly detect ADA additives in flour less than the prescribed standard (45 mg kg−1), which shows a great potential for visualization analysis and on-site detection of ADA in flour.