Identification of freshness and metabolite changes of royal jelly during storage using Nano-ESI-MS and UPLC-Q/TOF-MS

Royal jelly (RJ) is a highly perishable food during storage. However, the quality of RJ is hard to evaluate due to its complex and variable compositions. Nanoliter electrospray ionization mass spectrometry (nano-ESI-MS) is an emerging direct mass spectrometry method suitable for rapid analysis of complex food components and food quality. In this study, we investigated the freshness and metabolite changes of RJ stored at 4 °C and 25 °C using nano-ESI-MS and verified the results with UPLC-Q/TOF-MS. The nano-ESI-MS identified 20 compounds and quantified 9 metabolites with high stability and reproducibility. Multivariate analysis of the nano-ESI-MS data distinguished RJ of different freshness and suggested 45–60 and 7 days as the freshness threshold of RJ stored at 4 °C and 25 °C, respectively. The multivariate analysis of UPLC-Q/TOF-MS data output similar results to that of nano-ESI-MS. The relative abundance changes of metabolites identified by UPLC-Q/TOF-MS were approximately consistent with the quantification results of nano-ESI-MS, indicating the reliability of nano-ESI-MS in monitoring RJ freshness. This study proved the potential of nano-ESI-MS as a rapid method for monitoring RJ freshness and thus promoted the quality control of RJ during production.