No abstract

This study mainly explored the effects of low‐concentration salts (0.1, 0.5 mM NaCl and Na2SO4) on the gel, rheological and structural properties of fish gelatin (FG)–κ‐carrageenan (κC) polyelectrolyte hydrogels. The results showed that κC could increase the gel strength, hardness, and chewiness of the FG–κC polyelectrolyte hydrogels, while the addition of salts had a negative effect. The rheological behaviors showed that the addition of salts reduced the apparent viscosity, gel, and melting points of the FG–κC polyelectrolyte hydrogels. Compared with NaCl, Na2SO4‐treated FG–κC had lower gel strength, hardness, viscosity, gelation, and melting points, while the addition of salts increased the fluorescence intensity by unfolding FG molecules. The secondary structure analysis results showed that the addition of NaCl and Na2SO4 decreased α‐helix and β‐sheet contents of FG–κC by destroying the hydrogen bond of FG–κC.

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This study mainly evaluated the physical properties of kafirin‐quercetin (KQ) edible films and their application on the quality of cod fillets during cold storage. The results showed that the addition of quercetin significantly increased mechanical properties of KQ films, while decreased water vapor permeability, water solubility, and transparency. As quercetin was 0.4% (wt/vol), the film had the highest tensile strength (4.96 ± 1.23 MPa), the lowest water vapor permeability (1.08 ± 0.09 g·mm·m−2·h·KPa−1) and water solubility (22.02 ± 0.45%). Moreover, compared with the pure kafirin and polythylene films, KQ films could effectively inhibit the cod meat deterioration by restraining the growth of microorganisms and decreasing TVB‐N and TBARs. The KQ0.4% film was the best to prolong the shelf life of cod fillets during cold storage. Therefore, KQ edible films could be used as a potential food packaging material to protect and retain the quality of aquatic products.