Carbon Dots From Farmed Fish Blood as Novel Preservatives: Antioxidant, Antimicrobial Activities, and Shelf Life Extension of Refrigerated Slices From Asian Seabass Without and With Prior Bleeding.

Fish blood, an underutilized fish-processing byproduct, can serve as a sustainable precursor for multifunctional carbon dots (CDs). However, CDs synthesis from fish blood and the use of CDs for food preservation have not been explored. CDs were synthesized from different fractions of Asian seabass blood, including whole blood (WB-CDs), plasma (PB-CDs), and blood cells (CB-CDs). Physicochemical, antioxidant, antimicrobial, and preservative properties were evaluated. All synthesized CDs exhibited nanoscale dimensions, with good dispersion and distinct morphology. All CDs possessed UV-shielding capability, while WB-CDs and CB-CDs provided greater UV-A and UV-B blocking performance than PB-CDs. All CDs exhibited ABTS and DPPH radical scavenging activities, with CB-CDs showing highest antioxidant capacity, reducing power, and metal-chelating activity. In addition, all CDs inhibited the growth of major seafood spoilage bacteria, including Pseudomonas aeruginosa and Shewanella putrefaciens, whereas CB-CDs exhibited the strongest antimicrobial activity and low cytotoxicity. Owing to their favorable bioactivity, CB-CDs were selected for application at 250 and 500 ppm in bled and unbled Asian seabass fillets stored at 4°C for 15 days. CB-CD treatment significantly retarded the upsurge in pH, microbial counts, and lipid oxidation in a concentration-dependent manner. Fillets treated with 500 ppm CB-CDs achieved shelf lives of less than 15 days (bled) and less than 12 days (unbled), compared with less than 6 days for untreated controls. Furthermore, treated fillets retained higher levels of polyunsaturated fatty acids, indicating enhanced oxidative stability. These findings highlight the potential of blood-derived CDs as multifunctional nano-preservatives for seafood preservation while promoting fish blood valorization.