A Multi-Hurdle Approach for the Preservation of Rehydrated Cod: Ozonated Water Combined with High-Pressure Processing

Rehydrated cod (Gadus macrocephalus and Gadus morhua) is increasingly marketed as a ready-to- cook product. However, the rehydration process promotes physicochemical and microbiological changes that increase product perishability. In particular, the increase in water activity and the reduction in salt concentration favour microbial growth and accelerate product deterioration, resulting in limited shelf life even under refrigerated conditions.1,2 In this context, non-thermal preservation technologies are gaining attention as alternative preservation methods because they can improve microbial control while preserving product quality.3 This study evaluated the combined effect of high-pressure processing (HPP) and ozonated water on the microbiological quality and shelf life of vacuum-packed rehydrated cod fillets during refrigerated storage. Following rehydration and portioning, fillets were sprayed with ozonated water (2.0 ppm) or left as controls before HPP treatment (600 MPa for 5 min). A total of 12 independent trials were carried out. Microbiological analyses included total mesophilic counts (TMC), total psychrophilic counts (TPC), spoilage-associated microorganisms and selected foodborne pathogens, including Listeria monocytogenes and Salmonella spp. Sensory evaluation was also performed. Ozonated water spraying significantly reduced microbial loads immediately post-processing compared to controls, with lower TMC and TPC values in treated samples (p < 0.05). HPP also resulted in a significant reduction in microbial counts in both groups (p < 0.001), confirming its effectiveness as a post-packaging decontamination strategy. During storage, microbial populations increased over time, while ozonated samples exhibited lower TMC and TPC values than controls (p < 0.001). Pathogenic microorganisms were not detected in any sample. The isolates obtained were mainly represented by environmental and spoilage-associated bacteria commonly found in seafood- processing environments, particularly Pseudomonas, Staphylococcus, Serratia and Aeromonas spp. Overall, the combined application of ozonated water and HPP appears to be a promising multi-hurdle strategy for improving the microbiological stability of rehydrated cod.