This study investigated changes in the microbial compositions of crayfish tails during storage at 4 °C (for 0–12 days) as measured using high-throughput sequencing (HTS). The specific spoilage organisms (SSOs) in the crayfish tails were isolated using culture-dependent cultivation methods, and they were identified by 16S rRNA and characterized for their enzymatic spoilage potentials (e.g., protease, lipase, phospholipase, and amylase). The spoilage abilities of the selected strains in the crayfish tails were assessed by inoculating them into real food. Moreover, the microbial growth and the volatile basic nitrogen (TVB-N) changes were monitored during the storage period. The results from the HTS showed that the dominant genus of shrimp tails evolved from Streptococcus (D0) to Pseudomonas (D4) and, finally, to Paenisporosarcina (D12) during storage. Seven bacterial species (Acinetobacter lwoffii, Aeromonas veronii, Kurthia gibsonii, Pseudomonas sp., Exiguobacterium aurantiacum, Lelliottia amnigena, and Citrobacter freundii) were screened from the spoiled shrimp tails by the culture-dependent method, among which Aeromonas veronii had the strongest spoilage ability.

Chitosan nanoparticles loaded with gallic acid significantly improved the mechanical, barrier, antimicrobial and antioxidant properties of the composite film, giving it the potential to replace petroleum-based packaging films.

The purpose of this study is to obtain a bio-based coating with good functional activity and self-healing ability, demonstrating its potential in food, materials, and other application fields. Plastic coatings can cause serious environmental pollution. It was a good solution to replace plastic coatings with degradable coatings. However, the development of degradable coatings in the fields of food and materials was limited due to their insufficient antibacterial ability and weak comprehensive properties. Therefore, chitosan nanoparticles (NPs) loaded with gallic acid (GA) were self-assembled with gelatin (GE) to prepare high-performance, degradable, self-healing bio-based nanocomposite coatings with antibacterial and antioxidant properties. The oxygen permeability of GE nanocomposite coatings decreased gradually with the addition of NPs, and the barrier properties increased significantly. At the same time, due to the excellent antioxidant and antibacterial ability of GA, the antioxidant effect of the nanocomposite coatings increased by 119%, and the antibacterial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) increased by 32% and 58%, respectively, compared with the pure GE coatings. In addition, the nanocomposite coatings can be repaired within 24 h after being scratched at room temperature. Finally, GA coated with chitosan nanoparticles can significantly delay the escape of GA, and the retardation of gallic acid release exceeded 89% in simulated solutions after 24 h immersion, extending the service life of the nanocomposite coatings.

Crab roe sauce (CRS) is prone to spoilage due to microbial contamination. Therefore, this study aimed to investigate the inhibitory effects and mechanisms of a mixed bio-preservative (0.025% ε-polylysine hydrochloride (ε-PL) + 0.01% nisin (NS) + 0.01% tea polyphenols (TPs)) on the specific spoilage bacteria (SSB) in CRS. First, the SSB in CRS were isolated and identified by 16S rRNA sequencing. Two isolates were selected as representative strains based on their enzymatic spoilage potential and spoilage capability in CRS. By comparing the inhibition zones, ε-PL, NS, and TPs were selected from five conventional bio-preservatives (ε-PL, NS, TPs, grape seed extract (GSE), and rosemary extract (RE)) to prepare the mixed bio-preservative. The results showed that the minimum inhibitory concentration (MIC) of the mixed bio-preservative against Bacillus pumilus and Bacillus subtilis was 56.3 µg/mL. The growth curves and cell viability tests revealed that the mixed bio-preservative reduced the viability of both strains. The conductivity, alkaline phosphatase activity, and nucleic acid and soluble protein leakage indicated that the mixed bio-preservative disrupted the integrity of the cell walls and membranes of the two isolates in a concentration-dependent manner. Scanning electron microscopy further confirmed the damage to the cell membranes of the two isolates by the mixed bio-preservative. Overall, the mixed bio-preservative exhibited excellently inhibitory effects on the SSB and could be a promising method for the preservation of CRS.