Muscle Microbiome Analysis of Indian Mackerel ( <i>Rastrelliger kanagurta</i> ) Delineated Classical and Novel Spoilage Bacteria

Metagenomics allows a comprehensive insight into the spoilage-associated muscle microbiome shifts in the air-packed and vacuum-packed Indian mackerel. This study explored the microbial composition and diversity of spoilage flora in air-packed (T1M, T2M, and T3M) and vacuum-packed (T4M, T5M, and T6M) Indian mackerel (Rastrelliger kanagurta) stored at 0 ± 2°C (iced), 5 ± 2°C (chilled), and 30 ± 2°C (abused) temperatures through metagenomics, targeting the V1-V9 region of 16s rRNA. Total Volatile Base Nitrogen and Thiobarbituric Acid were analyzed to confirm the spoilage threshold limit, and accordingly, the fish muscle tissue on the spoilage day was selected for microbiome analysis. Metagenomic analysis revealed distinct variation in the relative abundance and spoilage microbiome between the air-packed and vacuum-packed Indian mackerel stored at iced, chilled, and abused temperatures. The predominant bacterial species responsible for spoilage were Cetobacterium ceti, Clostridium polyendosporum, and Gilliamella apicola in vacuum-packed mackerel, whereas Shewanella arctica, S. aquimarina, S. baltica, Staphylococcus xylosus, and Burkholderia cepacia played a major role in the spoilage of air-packed samples. The observed bacterial population dynamics across different temperatures and packaging significantly influenced the microbiome diversity in Indian mackerel. Summing up, this study emphasizes the unique and diverse microbes contributing to spoilage and provides a valuable guide for the flora that need to be controlled for extending the shelf life of Indian mackerel.