Microbial consortia in commercial salmon products: A comparative study using cultivation-dependent and high-throughput sequencing approaches

Despite the widespread consumption of salmon products, an all-round microbiological survey on fresh salmon and smoked salmon products sold on the market directly to consumers remains to be undertaken. The present study conducted a comprehensive microbial investigation employing both conventional cultivation-based techniques and 16S rRNA amplicon sequencing. A total of 120 fresh salmon and 95 smoked salmon products were systematically collected across all four seasons (spring, summer, fall, and winter), accompanied by temperature assessments of each product's interior. The average aerobic plate counts for fresh salmon and smoked salmon were 3.63 log and 1.36 log CFU/g, respectively, and the highest seasonal concentrations occurred in summer. The average coliform count was higher in fresh salmon (1.50 log CFU/g) than in smoked salmon products (1.12 log CFU/g). Although smoked salmon exhibited CFU counts similar to those of fresh salmon according to culture-based methods, 16S sequencing unveiled a distinct microbial composition. Photobacterium and Pseudomonas, recognized as major spoilage-related microorganisms, were the predominant genera in all products, but especially in fresh salmon. Smoked salmon exhibited diverse variations in bacterial composition compared to fresh salmon. Three types of lactic acid bacteria—Leuconostoc, Lactobacillus, and Lactococcus—were found to be significantly more abundant in smoked salmon than in fresh salmon. The outcomes of this study contribute to an enhanced understanding of retail salmon products, shedding light on crucial areas for investigation and suggesting potential interventions regarding both sales and production of salmon products.