Non-enzymatic browning in stored ready-to-eat oysters: Regional differences in color changes, chemical reactions and mechanisms

The whole oyster and its three independent parts (adductor muscle, visceral mass and mantle) were processed into ready-to-eat (RTE) samples and stored at 40 °C for 8 weeks. During storage, the whole oyster samples showed liquid exudation and progressive darkening. In contrast, the color of the visceral mass sample, mantle sample and whole oyster sample deteriorated more obviously than that of the adductor muscle sample. This may be due to the higher contents of transition metal ions, lipids and reducing sugars in the formers, which promote lipid oxidation, Maillard/Maillard-like reaction, and phenolic oxidation - the main cause of color deterioration. The exuding liquid, containing browning reaction substrates such as lipids, sugars and polyphenols as well as browning reaction products, directly stains the adductor muscle while also indirectly accelerating its browning reaction, ultimately leading to uniform discoloration throughout the whole oyster sample.