Unraveling the Effects of Biochemical Drivers on the Bacterial Communities and Volatile Profiles in Refrigerated Sturgeon Filets at 4°C

Abstract

Spoilage bacteria seriously influence the flavor and quality of fish meat. In this study, we investigated the quality characteristics, bacterial community, and volatile profiles of refrigerated (4°C) sturgeon filets during 10-day storage. On day 10, the refrigerated samples showed the lowest bacterial diversity and the largest difference in microbiota and biochemistry. The dominant genera in the fresh samples were Macrococcus, Acinetobacter, Moraxella, Brucella, and Pseudomonas, while the dominant bacteria changed into Acinetobacter, Carnobacterium, Macrococcus, Pseudomonas, and Psychrobacter at the end of storage. Our results suggest that these dominant taxa contribute to the spoilage of the refrigerated sturgeon filets. Meanwhile, during the storage, total viable counts, total volatile basic nitrogen, thiobarbituric acid-reactive substances, and trichloroacetic acid-soluble peptide significantly increased (P < 0.05), while the sensory score decreased steadily. Additionally, the ATP-related compounds and the K-value showed similarly increasing trends. The shelf-life of the refrigerated sturgeon filets was less than 8 days. The gas chromatography-ion mobility spectrometry results suggest that hexanal, ethyl acetate, ethanol, butanal, 1-propanol, isopentyl alcohol, 2-pentanone, 2-heptanone, ethyl propanoate, and propyl sulfide are potential chemical spoilage markers. The predicted metabolic pathways indicated an abundant carbohydrate metabolism and amino metabolism in the refrigerated sturgeon filets. This study provides insight into the determinants of sturgeon shelf-life and the spoilage process involved in refrigerated fish.

Keywords: GC-IMS; high-throughput sequencing; microbial communities; spoilage bacteria; volatile organic compounds.

FIGURE 1

Changes in sensory index (A), pH value (B), total volatile basic nitrogen (C), total viable counts (D), protein degradation (E), trichloroacetic acid-soluble peptides (F), thiobarbituric acid reactive substances (G), and nucleotide degradation products content and K-value (H) of sturgeon filets during storage at 4°C. The sensory scores were processed using Heml 1.0.3.7. Different lowercase letters indicate significant differences (P < 0.05) in the samples.

FIGURE 2

The volatile organic compounds (VOCs) identified in sturgeon filets on days 0, 4, and 10 during storage at 4°C. (A) Topographical plots corresponding to signals detected in samples and (B) fingerprint comparison of VOCs in samples determined by gas chromatography–ion mobility spectrometry.

FIGURE 3

The Venn diagram shows the unique and shared bacterial population (A), principal coordinate analysis of the bacterial community (B), dynamics in relative abundance (%) of bacterial community at genus level (C), and a heat map analysis of microbiota at the genus level (D) in sturgeon filets during storage at 4°C.

FIGURE 4

Functional properties that are related to microbial metabolism in the samples. (A) Comparison of bacterial metabolic pathways in refrigerated (4°C) sturgeon filets between days 4 and 10. (B) Relative abundance of the bacterial three-level metabolic pathways in the top 30. Metabolic inference based on the 16S rRNA sequence.

FIGURE 5

Network analysis of the correlation among microbiota, biochemical changes, and metabolic pathways. (A) Correlation between the dominant bacteria and biochemical changes. (B) Correlation between the dominant bacteria and metabolic pathways. The microbiota was considered at the operational taxonomic unit level, and statistically significant Pearson correlations were calculated among the sturgeon samples. A connection stands for a significant (P < 0.05) and positive (Pearson correlation > |0.7|) correlation. *p < 0.05, **p < 0.01, ***p < 0.001.