Synergistic effects of chilling and brining on the quality and safety of freshwater fish species from Western Ethiopian reservoirs

Abstract This study evaluated the independent and synergistic effects of chilled storage (4 °C) and 8% (w/v) brining on the quality, shelf-life, and safety of these species over 28-days. Nile tilapia ( Oreochromis niloticus ), African catfish ( Clarias gariepinus ), and Common carp ( Cyprinus carpio ) are primary protein sources in Fincha’a, Amarti, and Nashe area of Ethiopia, but their high moisture and enzymatic activity can drive rapid spoilage under ambient conditions. Fish from Fincha’a, Amarti, and Nashe reservoirs were subjected to four treatments: unsalted chilled (control), brining chilled (8% NaCl brine), storage periods, and fish species with corresponding ambient controls. Quality was assessed via pH dynamics, Total Volatile Basic Nitrogen (TVB-N), Total Viable Count (TVC), Psychrotrophic counts, and selective pathogen detection. A full factorial (3 × 4 × 2) experimental design GLM analyzed species, treatment, and time interactions. Chilling alone delayed spoilage but failed by day 7 (TVC > 7 log₁₀ CFU/g; TVB- N > 30 mg/100 g). In contrast, chilling combined with 8% brine extended the microbiological shelf-life to 14 days for Nile tilapia and African catfish based on TVC and TVB-N criteria, though Common carp exceeded the TVC limit by day 7. Presumptive v ibrio spp. emerged consistently by weeks 3–4 in brined samples, establishing a maximum safe storage limit of 14 days for brined-chilled Nile tilapia and African catfish. Common carp showed significantly higher microbial susceptibility than Nile tilapia or African catfish ( p < 0.001). While 8% brining combined with chilling significantly outperforms chilling alone, the delayed emergence of presumptive Vibrio species precludes storage beyond 14 days. These findings provide preliminary evidence-based safety guidance for small-scale fisheries in Ethiopia and similar resource-limited settings where continuous cold chain infrastructure is unavailable.