الفهرس 
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Abstract
• In this study, A total of forty catfish fillet samples of three different catfish species were randomly collected from Egyptian local markets and retailers during 2022 and 2023. Briefly, ten African catfish (Clarias gariepinus) ranging in weight from 600 to 1000 g, and ten silver catfish (Bagrus bayad) ranging in weight from 500 to 2500 g were purchased from different fish markets. Additionally, twenty skinless-frozen pangasius catfish (Pangasianodon hypophthalmus) fillets ranging in weight from 800–1000 g were obtained from different retailers. Pangasius catfish fillets can be divided into two grades: white basa fillets (grade I, white colour) and red basa fillets (grade II, pale pink to red colour).
• This study aimed to assess the physical, biochemical, sensory and microbiological parameters of catfish fillet samples. Firstly, the sensory attributes of raw catfish fillets were measured using a 9-point hedonic scale and these attributes include colour and appearance, odour, texture, and overall acceptability. Secondly, physical properties assessment include determination of colour and shear force. Thirdly, biochemical properties assessment include proximate composition (moisture, protein, fat and ash), pH, Total Volatile Base Nitrogen (TVB-N) and Thiobarbituric Acid Reactive Substances (TBARS). Finally, microbial assessment include enumeration of total aerobic, total aerobic psychrophilic, H2S producing bacteria, Staphylococci, Enterobacteriaceae, Coliforms and fecal Coliform counts and isolation of Salmonella spp., Staphylococcus aureus, Yersinia enterocolitica,
• Sensory attributes revealed that African catfish and silver catfish fillets showed significantly higher sensory scores than the pangasius catfish fillets. All the organoleptic properties of raw catfish fillets were above the rejection threshold score (≤4.0).
• Proximate composition showed that the African catfish and silver catfish fillets had significantly lower moisture (76.12-76.94) and higher crude protein (17.19-17.24) and fat levels (3.35-4.12) compared to the frozen pangasius catfish fillets.
• Total volatile basic nitrogen (TVB-N) ranged from 6.83 to 16.38 mg/100g, thiobarbituric acid-reactive substances (TBARS) values ranged from 0.35 to 1.01 mg malonaldehyde/kg and pH ranged from 6.43 to 7.35. The TVB-N and TBARS values of examined catfish fillets were within acceptable limits.
• Physical properties assessment revealed that African catfish fillets were darker and characterized by higher redness (a*) and lower yellowness (b*) values as well as higher shear force values (9.52 kgf/m3), while white basa fillet was the lowest darkness, less saturated with the red pigment (a*) and more saturated with the yellow component (b*) as well as lower shear values (2.17 kgf/m3) among the examined catfish fillets. The L* and a* colour attributes of the silver catfish and Pangasius catfish fillets were not significantly different. In contrast, pangasius catfish fillets had the lowest shear force values (<2.5 kgf/cm3). Thus, the pangasius catfish fillets were more tender than the African catfish and silver catfish fillets.
• Microbiological assessment revealed higher psychrophilic bacterial counts in Bagrus bayad fillets (5.21 log10 CFU g−1) than Clarias gariepinus fillets (4.31 log10 CFU g−1) and Pangasianodon hypophthalmus fillets (3.89–4.7 log10 CFU g−1). The total aerobic, Staphylococci, H2S producing bacteria, Enterobacteriaceae, and Coliform counts showed no significant differences among the examined catfish fillets.
• The fecal Coliform density in Clarias gariepinus fillet samples (1.27 log10 MPN g−1) was significantly higher than Bagrus bayad fillets (0.91 log10 MPN g−1) and Pangasianodon hypophthalmus fillets (0.50-0.56 log10 MPN g−1). These levels were lower than the upper acceptable microbiological limits for fish fillets.
• No Salmonella spp., Vibrio spp., Yersinia enterocolitica isolates could be detected in catfish fillets. By contrast, the qualitative microbiological analyses revealed isolation of Escherichia spp., Aeromonas spp. and Pseudomonas spp. Moreover, Escherichia spp. was detected in five African catfish fillets, three silver catfish fillets and two pangasius catfish fillets. Aeromonas spp. were detected in five African catfish fillets, four silver catfish fillets, and five pangasius catfish fillets (one from white basa fillet and four from red basa fillets). On the contrary, Pseudomonas spp. was detected in four pangasius catfish fillets (one from white basa fillet and three from red basa fillets).
• These isolates were identified based on 16S rRNA sequencing and phylogenetic analyses. The phenotypically identified Escherichia isolates were assigned to E. coli and E. fergusonii, while the phenotypically identified Aeromonas isolates were assigned to Aeromonas hydrophila. Further, the phenotypically identified Pseudomonas isolates were assigned to Pseudomonas luteola using 16S rRNA sequencing and phylogenetic analyses.
• The serological identification of nine Escherichia coli and Escherichia fergusonii isolates serologically identified using O antigen. In this study, E. coli serotype O26 was isolated from African catfish and silver catfish fillets, and E. fergusonii serotype O78 from two different African catfish fillets.
• This study highlights the sensory, biochemical, physical, and microbiological assessment of three catfish species and concluded that the fillet samples of these catfish were of superior quality and acceptable for human consumption.