Validation, measurement uncertainty, and application of analytical methods for flavor enhancers in processed foods distributed in Korea

Flavor enhancers, such as L-glutamic acid, glycine, guanosine monophosphate (GMP), and inosine monophosphate (IMP), are widely used in processed foods to intensify the umami taste. This study optimized the extraction conditions of monosodium glutamate by evaluating temperature and time to enhance recovery. Following optimization, HPLC-DAD methods were developed and validated for the simultaneous quantification of flavor enhancers, while LC-MS/MS was used for qualitative confirmation to ensure specificity. The method demonstrated excellent linearity (r² ≥ 0.9999), sensitivity (LOD 0.04–0.41 mg/L, LOQ 0.13–1.25 mg/L), accuracy (85.8–104.5 %), and precision (RSD ≤ 4.7 %), meeting the AOAC criteria. L-Glutamic acid and glycine were detected in all samples (100 %), while GMP and IMP were found in over 96 %. Inter-laboratory validation and measurement uncertainty analysis confirmed the method's robustness and reproducibility. A total of 858 processed food samples from 28 categories were analyzed to assess their distribution. This study not only provides an analytical protocol but also expands upon previous methods by enabling simultaneous quantification of a wider range of flavor enhancers across processed food matrices. The method offers a scientific foundation for dietary exposure assessment, regulatory monitoring, and food standard development, and is expected to support quality control in the food industry and safeguard consumer health.