Effect of co-inoculation of Pseudomonas fragi and Pseudomonas putida on the spoilage of chilled pork after the screening of a variety of different combinations of two Pseudomonas species

This study preliminarily evaluated the effect of different combinations of two Pseudomonas species (P. fragi, P. lundensis, P. fluorescens, and P. putida) on the protein degradation capacity of meat and bacteria growth rules. Then P. fragi and P. putida, with the co-spoilage potential, were inoculated on pork to determine the ability of spoilage, and the potential spoilage genes further were revealed by whole genome sequencing. Results showed that, in the P. fragi + P. putida and P. fragi + P. fluorescens group, the diameter of Raw-pork Juice Agar (RJA) decomposition zone was significantly higher than that in the single-inoculated group, respectively. Furthermore, the results in situ showed that P. fragi and P. putida grew rapidly after co-culture, in which μ_max was significantly higher than that in the single-inoculated group. In addition, at the end of storage, the pH and TVB-N values of pork after co-culture were significantly higher than those of the single-inoculated group, and the texture of pork was softer. Simultaneously, the contents of volatile organic compounds including 1-Octen-3-ol, 2-Nonanone, and Hexanal, were significantly increased after co-culture. Moreover, the genes of P. fragi and P. putida, identified by whole genome sequencing, related to amino acid metabolism, carbohydrate metabolism, and motor chemotaxis may be the primary reasons involved in the co-spoilage of pork. In conclusion, this study demonstrated that P. fragi and P. putida had a synergistic interaction to accelerate the spoilage of pork, which could provide a better understanding of co-spoilage of different Pseudomonas spp.