Abstract
The purpose of this study was to evaluate the effect of an active gelatin coating containing eugenol and vacuum on the microbial diversity of Chinese seabass (Lateolabrax maculatus) during cold (−0.9 °C) storage. The bacterial sequences in Chinese seabass were observed using a high-throughput sequencing technique targeting the V3–V4 region of the 16S Ribosomal DNA (rDNA) on 0, 12th, and 24th day, which showed a more comprehensive estimate of the microbial diversity in seabass samples compared with microbial enumeration. The results revealed that the species diversity of fresh seabass was rich, mainly including Carnobacterium, Glutamicibacter, and Pseudomonas, with abundance ratios of 0.286, 0.160, and 0.130, respectively. Pseudomonas and Shewanella were the primary contaminants in the spoiled control samples, where the abundance ratios increased from 0.220 and 0.174 on the 12th day to 0.802 and 0.163 on the 24th day, respectively. Vacuum treatment could inhibit the growth of Pseudomonas and Shewanella such that when stored on the 12th day, Brochothrix became the superior genus. However, Pseudomonas and Shewanella dominated the storage until the 24th day, where their abundance ratios were 0.343 and 0.279, respectively. The inhibition of Pseudomonas and Carnobacterium was gradually enhanced with increasing concentrations of eugenol. Furthermore, an active gelatin coating containing eugenol and vacuum treatment was more effective at inhibiting the increase of the total volatile basic nitrogen. This study confirmed that an active gelatin coating containing eugenol and vacuum could reduce the species of bacteria, inhibit the growth and reproduction of the main dominant spoilage bacteria, and delay the spoilage of seabass.
Highlights
Chinese seabass (Lateolabrax maculatus) is one of the most economically significant cultured fish with a high yield in China [1,2]
total volatile basic nitrogen (TVB-N) analysis has traditionally been used as an indicator of fish quality [48] and a value higher than 25 mg N/100 g indicates that a fish is unfit for human consumption [49]
After the seabass fillet samples were stored for 24 days, the relative abundances of Pseudomonas in the G-0.075E + VP, G-0.15E + VP, and G-0.30E + VP samples were 0.343, 0.379, and 0.081, respectively; the relative abundances of the Carnobacterium were 0.547, 0.447, and 0.044, respectively; the relative abundances of Shewanella were 0.006, 0.157, and 0.579, respectively. These results indicated that vacuum packaging combined with the active gelatin coating containing high concentrations of eugenol can effectively inhibit the growth of Pseudomonas and Carnobacterium
Summary
Chinese seabass (Lateolabrax maculatus) is one of the most economically significant cultured fish with a high yield in China [1,2]. Given that the shelf life of vacuum-packaged aquatic products is relatively short because of the activity of spoilage microorganisms, research on new preservation methods that can inhibit the growth of these microorganisms is required [8]. Active coatings with antimicrobial properties have been extensively studied and are applied in food preservation to inhibit the growth of microorganisms, thereby extending the shelf life [9,10,11]. Active coatings are usually composed of polysaccharides, proteins, and lipids, and can act as a carrier for natural antioxidants and antimicrobial agents to improve the quality of fresh food [12,13,14]. Proteins possess a good film-forming ability and have been used as edible food packaging materials [15]. Fish gelatin is an excellent material with good film-forming ability and oxygen barrier properties [16]
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