In addition to microbial spoilage and lipid peroxidation, protein oxidation is increasingly recognized as a major cause for quality deterioration of muscle-based foods. Although protein oxidation in muscle-based foods has attracted tremendous interest in the past decade, specific oxidative pathways and underlying mechanisms of protein oxidation in aquatic products remain largely unexplored. The present review covers the aspects of the origin and site-specific nature of protein oxidation, progress on the characterization of protein oxidation, oxidized proteins in aquatic products, and impact of protein oxidation on protein functionalities. Compared to meat protein oxidation, aquatic proteins demonstrate a less extent of oxidation on aromatic amino acids and are more susceptible to be indirectly oxidized by lipid peroxidation products. Different from traditional measurement of protein carbonyls and thiols, proteomics-based strategy better characterizes the targeted oxidation sites within proteins. The future trends using more robust and accurate targeted proteomics, such as parallel reaction monitoring strategy, to characterize protein oxidation in aquatic products are also given.

Quercetin is a flavonoid that has been shown to have health-promoting capacities due to its potent antioxidant activity. However, the effect of chronic intake of quercetin on the gut microbiome and diabetes-related biomarkers remains unclear. Male C57BL/6J mice were fed HF or HF supplemented with 0.05% quercetin (HFQ) for 6 weeks. Diabetes-related biomarkers in blood were determined in mice fed high-fat (HF) diets supplemented with quercetin. Mice fed the HFQ diet gained less body, liver, and adipose weight, while liver lipid and blood glucose levels were also lowered. Diabetes-related plasma biomarkers insulin, leptin, resistin, and glucagon were significantly reduced by quercetin supplementation. In feces, quercetin supplementation significantly increased the relative abundance of Akkermansia and decreased the Firmicutes/Bacteroidetes ratio. The expression of genes Srebf1, Ppara, Cyp51, Scd1, and Fasn was downregulated by quercetin supplementation. These results indicated that diabetes biomarkers are associated with early metabolic changes accompanying obesity, and quercetin may ameliorate insulin resistance.

The demand for caviar has increased in recent years because of its high nutritional and commercial values. Consequently, the wild population of sturgeon has decreased. This has shifted the balance of supply of caviar from wild sturgeon to more from farmed fish. The development of aquaculture has resulted in many technical advances of sturgeon rearing. The same factors that encouraged sturgeon farming have also stimulated the search for alternative products optimizing wild-sourced caviar utilization and even created some new market opportunities. Caviar substitutes have been obtained from at least 38 fish species (other than sturgeon) and aquatic animals, e.g., sea urchin, sea cucumber and snails. Although, the emergence of products has not always been positive, as the sturgeon caviar market has been impacted by commercial mimicry, fraud, and mislabeling of caviar-substitutes. This review provides information about the global production and trade of sturgeon, caviar, and caviar substitutes. In addition, the physics, gastronomy, and the quality changes of caviar and caviar substitutes during different fish-harvesting steps are discussed. Moreover, information about commercial mimicry, fraud, and new methods to detect these criminal acts are considered.