Effects of Latilactobacillus fuchuensis and marination on spoilage and tyramine formation in rainbow trout packaged under modified atmosphere.

Latilactobacillus fuchuensis has been detected in refrigerated foods, but its role in fish spoilage and biogenic amine formation remains poorly understood. This study provides an endpoint-based, screening-level assessment of the impact of tyramine-producing (tdc+) and non-producing (tdc-) L. fuchuensis strains on microbial growth, tyramine formation, and sensory quality in a realistic food matrix. Marinated and unmarinated rainbow trout fillets were stored under modified atmosphere at 3 °C for 12 days. L. fuchuensis grew in both products, reaching higher levels in marinated fillets. In marinated samples, its growth coincided with a reduction in pH, indicating active acidification of the fish matrix. Tyramine accumulation was strongly influenced by both marination and strain type: marinated fillets inoculated with tdc+ strains reached up to 67 mg/kg tyramine, whereas tdc- strains produced only low amounts. In unmarinated fillets, tyramine concentrations were lower and did not differ between strain types. Sensory evaluation indicated a more rapid loss of sensory quality in inoculated samples compared with controls, suggesting that L. fuchuensis contributes to spoilage-associated changes in rainbow trout. Overall, these findings demonstrate that marination promotes the growth of L. fuchuensis and enhances tyramine formation in rainbow trout stored under modified atmosphere. The results further indicate that spoilage potential and biogenic amine risk cannot be inferred solely at the species level but depend on strain-specific properties.