Aeromonas spp. are commonly found in spoilage of chilled meat. Aeromonas salmonicida NCM 29 and Aeromonas salmonicida NCM 57 have been discovered the spoilage heterogeneity in degrading myofibrillar protein. In this study, the two strains were tested to uncover the discrepancy of meat spoilage in collagen-rich chilled meat and extracted collagen. The results revealed that chicken claws, riched in collagen, inoculated with NCM 29 showed higher values of total viable counts (TVC), total volatile basic nitrogen (TVB-N), pH, adhered cells, TCA-soluble peptides, and protease activity compared to those inoculated with NCM 57. Furthermore, NCM 29 generated higher quantity of volatile organic compounds related to meat spoilage. The collagenase (hemagglutinin protease, Hap) secreted by NCM 29 has been identified as the key factor responsible for the observed discrepancies in spoilage, which gradually degraded collagen into peptides and hydroxyproline. The capacity of Hap to degrade type I collagen in vitro indicated that it has apparent proteolytic activity, which could reduce the average particle size and alter secondary structure of collagen. SDS-PAGE further confirmed the degradation of the β chain in collagen. These findings not only provide a theoretical basis for in-depth investigation of the meat spoilage mechanisms of Aeromonas spp., but also encourage us to take measures to avoid the spoilage of related bacteria such as Aeromonas spp. during the preservation process.

Chilled chicken is inevitably contaminated by microorganisms during slaughtering and processing, resulting in spoilage. Cutting parts of chilled chicken, especially wings, feet, and other skin-on products, are abundant in collagen, which may be the primary target for degradation by spoilage microorganisms. In this work, a total of 17 isolates of spoilage bacteria that could secrete both collagenase and lipase were determined by raw-chicken juice agar (RJA) method, and the results showed that 7 strains of Serratia, Aeromonas, and Pseudomonas could significantly decompose the collagen ingredients. The gelatin zymography showed that Serratia liquefaciens (F5) and Pseudomonas saponiphila (G7) had apparent degradation bands around 50 kDa, and Aeromonas veronii (G8) and Aeromonas salmonicida (H8) had a band around 65 and 95 kDa, respectively. The lipase and collagenase activities were detected isolate-by-isolate, with F5 showing the highest collagenase activity. For spoilage ability on meat in situ, F5 performed strongest in spoilage ability, indicated by the total viable counts, total volatile basic nitrogen content, sensory scores, lipase, and collagenase activity. This study provides a theoretical basis for spoilage heterogeneity of strains with high-producing collagenase in meat.

The aim of this study was to evaluate the factors influencing the inactivation effect of intense pulsed light (IPL) on Aeromonas salmonicida grown on chicken meat and skin, and to further develop prediction models of inactivation. In this work, chicken meat and skin inoculated with meat-borne A. salmonicida isolates were subjected to IPL treatments under different conditions. The results showed that IPL had obvious bactericidal effect in the chicken skin and thickness groups when the treatment voltage and time were 7 V combined with 5 s. In addition, the lethality curves of A. salmonicida were fitted under IPL conditions of 3.5–7.5 V. The comparison of statistical parameters revealed that the Weibull model could best fit the mortality curves and could accurately predict the mortality dynamic of A. salmonicida grown on chicken skin. And further a secondary model between the scale factor b and the treatment voltage in Weibull model was established using linear equations, which determined that the secondary model could accurately predict the inactivation of A. salmonicida. This study provides a theoretical basis for future prediction models of Aeromonas, and also provides new ideas for sterilization approaches of meat-borne Aeromonas.

Salmonella and their biofilm formation are the primary bacterial causes of foodborne outbreaks and cross-contamination. The objective of the study was to investigate the potential of Salmonella phages as an alternative technology for biofilm removal. In this work, 21 Salmonella phages were isolated from a chicken farm and slaughter plant and the phage (CW1) with the broadest spectrum was characterized. Complete genome sequence analysis revealed that the genomes of phage CW1 is composed of 41763 bp with 58 open reading frames (ORFs) and a holin-endolysin system and it does not encode any virulence or lysogeny. A phage cocktail consisted of CW1 (with the broadest spectrum of 70.49%) and CW11, M4 and M10 (with a high lytic activity of more than 67.11%) was established. Treatment with the cocktail reduced the cells in the developing biofilm and mature biofilm by 0.79 lg(CFU/cm²) and 0.4 lg(CFU/cm²), respectively. More dead cells and scattered extracellular polymeric substances (EPS) were observed by confocal laser scanning microscopy and scanning electron microscopy. Raman analysis found that carbohydrates and proteins were the identification receptors for scattered EPS. This finding suggests that this phage cocktail has potential applications for the sterilization of Salmonella biofilm during meat processing.