Preparation of chitosan oligosaccharide-porphyrin conjugate and its photodynamic preservation effect on Litopenaeus vannamei.

Spoilage of refrigerated aquatic products remains a challenge, requiring safe, effective preservation strategies. A promising chitosan oligosaccharide-porphyrin photosensitizer (COS-N-(Br-TPP)), was synthesized and evaluated for photodynamic inactivation (PDI) preservation of refrigerated Litopenaeus vannamei. The saturated solubility was 1.00 mg/mL, due to COS chains increasing polarity/hydrogen bonding. Compared with Br-TPP, COS-N-(Br-TPP) showed 27.89% higher photostability, improved thermal stability (107.14 to 162.19 °C) and singlet oxygen (1O2) generation. For conjugate (n = 3), the smallest ΔEst(S1-T4) (0.061 eV) and largest SOC(S1/T4) (0.199 cm-1) indicated enhanced intersystem crossing, favoring 1O2 generation. PDI at 4 °C (20 μmol/L COS-N-(Br-TPP), 30 min immersion, LED 450 nm, 20 mW/cm2, 40 min) improved sensory, color stability and inhibited pH (7.05 at 8 d), TVB-N (22.68 mg/100 g at 6 d), TVC (6.04 log CFU/g at 6 d), and MDA (15.48 nmol/g at 8 d) increases in Litopenaeus vannamei. With no obvious cytotoxicity, COS-N-(Br-TPP) was a promising water-soluble photosensitizer for aquatic products preservation.