Effect of lipid oxidation on quality attributes and control technologies in dried aquatic animal products: a critical review

Insight into the mechanism of Maillard reaction and lipids mutually contribute to the flavor release of squid fillets during the drying process

Dried squid fillet is a popular seafood product with a unique flavor. However, its flavor release mechanism is unclear. In this study, volatile compounds (VOCs) were dynamically monitored in thawed squid (TS), salted squid (SS) and dried squid for 6 h (D6) and 24 h (D24). Subsequently, the Maillard reaction (MR) substrate, lipid oxidation index, free fatty acids and lipid profiles were detected. The results showed that the number of VOCs increased from 11 in TS (114.26 μg/kg) to 19 in D24 (1257.89 μg/kg). Besides, MR between glucose/ribose and amino acids (methionine, arginine, etc.) contributed to 3-methyl-butanal, methional and 2,3-butanedione. Meanwhile, lipid oxidation index, lipidomics and correlation analysis indicated that lipids (phosphatidylcholines and triglycerides) containing polyunsaturated fatty acids (C18:2, C20:4, C20:5 and C22:6) were precursors of 3-methyl-butanal, nonanal, heptanal, dodecane and tetradecane. Briefly, lipid hydrolysis, oxidation and MR mutually contributed to the flavor during the drying process of squid fillets.

Regulating effects of low salt dry-curing pre-treatment on microbiota, biochemical changes and flavour precursors of grass carp (Ctenopharyngodon idella) fillets during storage at 4 °C

Low salt dry-curing (LSD), as a healthier pre-treatment for the preservation of fishery products, is a potential technique substitute for excessively salty curing. The regulatory effects of 2 % and 3 % LSD on the quality evolution through an intrinsic correlation between microbiota succession and flavour precursors of refrigerated grass carp fillets were investigated in this study. The results showed that the LSD pre-treatment was effective in promoting proteolysis, free amino acid and fatty acid metabolism with the microbiota succession and quality evolution. Compared with unpre-treated samples, the 3 % LSD pre-treatment effectively extended the shelf life by 10 days within the acceptable quality attributes. Not only did the LSD pre-treatment lead to catalytic microbiota succession and inhibitive spoilage substance production but it also improved the flavour precursors, which are taste-active amino acids and polyunsaturated fatty acids (PUFAs). Moreover, considerable correlations between quality attributes, taste-active amino acids, PUFAs and microbiota were obtained.

Encapsulation Alleviates the Auto-browning of Epigallocatechin-3-gallate in Aqueous Solutions through Regulating Molecular Self-Aggregation Behavior

Catechins are widely recognized for superb antioxidant capability, but their application as food antioxidants is hindered by susceptibility to auto-browning under high-moisture conditions. Here, we proposed a strategy of ordered encapsulation with cyclodextrin-based metal-organic frameworks (CD-MOFs) to alleviate the auto-browning phenomenon of catechins while preserving their antioxidant capability and demonstrated the feasibility of this strategy via selecting epigallocatechin-3-gallate (EGCG) as a model. Even in aqueous solutions, EGCG@CD-MOFs still possessed delayed browning, in contrast with pristine EGCG, characterized by suppressed efficiencies on the generation of oxidative dimers (theasinensin A) and semiquinone radicals. Mechanism insights revealed that ordered encapsulation brought dual regulations on the self-aggregation behavior of EGCG: EGCG@CD-MOFs exhibited a gradual structural collapse from the framework toward irregular aggregates as O-K bonds broke progressively, which restricted molecular mobility of EGCG, and EGCG molecular conformations became constrained by the structure of EGCG@CD-MOFs as well as rich intermolecular forces, even after structural collapse.