NMR Tracking of metabolomic changes during the fermentation process of maatjes

This research project focused on authenticating and differentiating maatjes products, particularly Glückstädter Matjes PGI and Dutch maatjesharing TSG, based on their metabolite profiles. These traditional products are fermented using the fish's own pancreatic enzymes, as set out in EU Regulations 2015/823 and 2015/1745. The production of opposing products Matjes nordischer Art and Heringsfilet nach Matjesart gesalzen is however simplified and accelerated using exogenous enzymes.[1] Previous research on the fermentation of fish products has mainly focused on the influence of microorganisms, but the changes that occur in the metabolome during maatjes maturation remain unknown.[2] NMR spectroscopy is well suited for the authentication of food products due to its non‐targeted properties but it also allows for marker identification to differentiate between fermentation processes. [3] The aim of this study was therefore to use NMR spectroscopy and chemometric methods to create classification models that are able to reliably determine the origin and production process of these herring‐based products. Based on 1 H‐NMR spectra of the polar and non‐polar extracts of herring and traditional maatjes samples, highly precise classification models were created, and the signals relevant for differentiation identified. The fermentation process was monitored in model systems using the fish's endogenous pancreatic enzymes as well as exogenous enzymes from commercially available maturation kits. Results based on 1 H and 31 P NMR spectroscopy indicate variabilities in protease activity and further suggest an influence of pancreatic phospholipase. The findings confirm that NMR‐based metabolomics are a promising tool for the authentication and quality assurance of Maatjes products while being suited for routine application. They provide valuable insights into the metabolomic changes induced by fermentation of traditionally and accelerated‐fermented maatjes products, thereby contributing to consumer protection and ensuring the preservation of regional products.