From discoloration to color enhancement: A novel approach to high-concentration tannic acid detection based on VCo-N-C bimetallic Nanozyme

The direct and rapid detection of high-concentration tannic acid (TA) was crucial for food quality monitoring. In this study, a TA detection system was developed based on a binary metal V and Co-enclosed carbon substrate (VCo-N-C) nanozyme with laccase-like activity, which innovatively shifted the conventional detection approach from the 3,3',5,5'-tetramethylbenzidine (TMB) discoloration principle to the 4-aminoantipyrine(4-AP) color enhancement principle. In the presence of VCo-N-C, 4-AP specifically bound to the oxidation products of TA, resulting in a brown-red compound. The sensing platform reduced the reaction time to 10 min and extended the detection range to 0.1-3000 mg/L (R² > 0.99). Ultimately, the VCo-N-C&4-AP system was successfully applied to detect TA content in high-concentration actual samples such as brandy, white liquor, and tea beverages without the need of pretreatment. This study provided a new and powerful strategy for food quality control and monitoring.