Tangerine peel-derived carbon dots as natural antioxidant and antimicrobial agents for extending the shelf life of precooked baby clam edible portion

• CDs were synthesized from peels of three tangerine cultivars (BM, CK, SNP) • BM-CDs showed the excellent UV-blocking abilities against UV-A and UV-B • SNP-CDs had higher antioxidant and antimicrobial activities than others • CDs could serve as a preservative for precooked baby clam edible portion (PBC-EP) • All CDs delayed lipid oxidation and reduced microbial growth in refrigerated PBC-EP Multi-functional properties of carbon dots (CDs) synthesized from tangerine peels with different cultivars [bangmod (BM-CDs), chokun (CK-CDs) and sai nam pung (SNP-CDs)] and their application in preserving precooked baby clam edible portion (PBC-EP) samples were investigated. The synthesized CDs had nanoscale in sizes ranging from ∼2.24 to 6.83 nm, and SNP-CDs showed the smallest size and most uniform dispersion. All CDs demonstrated strong UV-shielding ability. BM-CDs showed superior UV-A and UV-B blocking performance to others, mainly owing to its π-π* transition. In general, higher radical scavenging activity (RS-A) against ABTS was observed than that toward DPPH, with SNP-CDs displaying the strongest overall antioxidant capacity (P<0.05). Antimicrobial analysis indicated that all CDs effectively inhibited both fungi including Aspergillus flavus (AF), Aspergillus parasiticus (AP) and bacteria involving Shewanella putrefaciens (SP), Listeria monocytogenes (LM) and Escherichia coli (EC). Among all, SNP-CDs showed the most effective inhibition. Nonetheless, their activity against Pseudomonas aeruginosa (PA) was relatively weaker. When all three CDs at 300 ppm were applied in PBC-EP samples stored at 4°C (12 days), the lower increases in pH, microbial counts and lipid oxidation were obtained when compared to the control. Overall, the findings highlighted the multifunctionalities of CDs from tangerine peels as natural UV barriers, antioxidants and antimicrobial agents. As a consequence, they could serve as sustainable potential alternatives to synthetic additives for seafood preservation.