In order to address the challenges of low yield, inadequate gel strength, and high susceptibility to melting at ambient temperature in the industrial production of large yellow croaker aspic, this study evaluated the effect of agar-gelatin blends on its appearance, overall sensory score, hardness, brittleness, and springiness. It determined the optimal blend ratio and total concentration, assessed the effect of the optimal blend on the product’s yield, melt resistance, and overall quality, and elucidated the underlying mechanisms using Fourier transform infrared spectroscopy (FTIR), low-field nuclear magnetic resonance (LF-NMR), and scanning electron microscopy (SEM). The optimal formulation consisted of agar and gelatin at a mass ratio of 1:1 with a total concentration of 1.0 g/100 mL. Under these conditions, the yield of fish aspic significantly increased compared with that of traditional yellow croaker aspic (44.30% vs. 24.62%; P < 0.01). The product retained its integral three-dimensional shape after 4 hours at 30 ℃; its mass loss rate decreased significantly, and its springiness (9.59 mm) and gel strength (510.80 g·mm) increased relative to traditional fish aspic. Meanwhile, no significant differences were found between them in moisture, ash, or fat contents (P > 0.05), nor were any visually perceptible changes in color observed. Fourier transform infrared spectroscopy analysis indicated the presence of hydrogen bonding, weak electrostatic interactions, or hydrophobic interactions between the agar-gelatin blend and the aspic matrix. Low-field nuclear magnetic resonance analysis demonstrated the agar-gelatin blend enhanced the water-binding capacity of the aspic, and scanning electron microscope revealed that the agar-gelatin blend reduced the pore size. These findings offer a scientific foundation and technical support for the industrial application and standardized production of large yellow croaker aspic.

In this study, a multifunctional aptamer-conjugated magnetic covalent organic framework (COF)-CuO/Au nanozyme (MCOF-CuO/Au@apt) was developed as a “three-in-one” platform for dual-signal colorimetric and fluorescent detection of Vibrio parahaemolyticus. The nanozyme integrated magnetic separation, peroxidase-like catalytic activity, and specific target recognition through an aptamer-based strategy. Upon binding to V. parahaemolyticus, the catalytic oxidation of tetra-aminophenylethylene (TPE-4A) by the nanozyme was selectively inhibited, resulting in distinct colorimetric and fluorescent signals that significantly enhanced the detection accuracy and reliability. The proposed method exhibited high sensitivity, with limits of detection (LOD) of 21 and 7 CFU/mL for the colorimetric and fluorescent assays, respectively. The performance of this method was validated using real seafood samples, including Penaeus vannamei, Mytilus coruscus, and Crassostrea gigas, which showed high recovery rates (101.11%–107.30%) and excellent reproducibility. The system also demonstrated strong specificity and accuracy under various conditions, confirming its robustness and practical applicability. Collectively, this innovative platform presents a promising solution for the rapid, versatile, and sensitive detection of V. parahaemolyticus in seafood, with considerable potential to advance food safety diagnosis and on-site monitoring.

Pullulan (PUL) and polyvinyl alcohol (PVA)-based nanofiber film (PUL-PVA-BAE) loaded with bayberry pomace anthocyanin extract (BAE) has good pH response. However, due to the high hydrophilicity of PUL-PVA-BAE, its stability needs to be improved for its application as a freshness indicator label in high humidity environments. In this study, a double-layered nanofiber film (ZG/PUL-PVA-BAE) was prepared by incorporating a hydrophobic layer consisting of zein and gelatin (ZG) onto PUL-PVA-BAE, and its physical properties, structure, color response, stability, and application were studied. The results showed that the surface of the double-layered film was smooth with uniform fiber distribution, in which PUL-PVA-BAE was successfully fixed on the hydrophobic layer through intermolecular hydrogen bonding. After the addition of the hydrophobic layer, the water resistance and mechanical properties of the nanofiber film were improved. Specifically, the water solubility decreased from 84.01% to 63.62%, and water vapor permeability from 2.52 to 2.01 g·mm/(m²·Pa·s·10⁵); the tensile strength increased from 1.74 to 2.64 MPa, and elongation at break from 15.08% to 23.29%. There were no significant changes in pH sensitivity, color response, reversibility, or stability between the single-layered and double-layered films. The double-layered film could discriminate the freshness state (fresh, sub-fresh, and spoiled) of Penaeus vannamei stored at 4 ℃ based on color changes (purple red, gray purple or gray green and green), which showed similar color changes to the single-layered film. In conclusion, the double-layered nanofiber film still functions as a freshness indicator while showing improved morphological stability in high humidity environments, offering technical support for aquatic product freshness monitoring.