Evaluation of the underestimation of citrinin content in Hongqu using hydrolysis treatments and UPLC-FLD

Modified mycotoxins can cause an underestimation of exposure risk due to their untraceable characteristics. Hongqu, a traditional Chinese fermented product, is widely used as food colorants, fermenters and functional foods for about 2000 years. Though there were several methods to reduce citrinin (CIT) content in Hongqu, the risk assessment and prevention of modified CIT remain inadequate, causing potential risk to human health. The current study firstly identified the occurrence of modified CIT in Hongqu via acid, alkaline and enzyme hydrolysis combined with chromatographic and mass spectrometric approaches. Then 8 Hongqu samples and 5 Monascus products were treated using the optimized acid hydrolysis method and analyzed by ultra-high-performance liquid chromatography with fluorescence detector. The results showed that CIT content in the CIT positive Hongqu increased by 35.28%–458.13% after acid hydrolysis, demonstrating there could be a underestimation risk in the CIT positive Hongqu samples, and the modification of CIT might not be chemical modified, but matrix associated.