Enhanced photodynamic inactivation against Listeria monocytogenes under blue light mediated by carbon dots derived from 'Shatian' pomelo peels for ready-to-eat sausage preservation.

Listeria monocytogenes (L. monocytogenes) as the main cause for sausage cross-contamination poses a serious threat to public health. Photodynamic inactivation (PDI) as a non-thermal food sterilization technology has attracted attention, while the efficiency of photosensitizers is restricted by poor water solubility and chemical instability. Carbon dots (CDs) had been regarded as the promising candidates because of the small size, water solubility, and low photobleaching rates. Herein, the CDs were synthesized from 'Shatian' pomelo peels waste via hydrothermal synthesis. The prepared CDs exhibited a small particle size (4.23 ± 1.65 nm), non-cytotoxicity (up to 512 μg/mL), fluorescence, antioxidant property, and the surface groups such as hydroxyl, which improved the antibacterial activity against L. monocytogenes. Furthermore, an enhanced PDI against L. monocytogenes mediated by CDs under blue light (BL-405 nm) was observed, which resulted in a nearly complete bacterial inactivation when exposure to CDs at the concentration of 0.5 mg/mL and BL-405 nm (320 J/cm2). CDs efficiently penetrated cell membranes to induce intracellular oxidative stress, cause lipid peroxidation, thereby disrupting cell membrane integrity, and eventually leading to intracellular materials leakage and cell death. Moreover, CDs mediated BL-405 nm irradiation effectively reduced L. monocytogenes contamination in ready-to-eat sausage, and extended the shelf life by delaying the deterioration, such as color, texture, pH and lipid oxidation. These findings provided a novel approach for agricultural by-products utilization and developed a new green food preservation strategy.