Effects of ultraviolet light and curcumin-mediated photodynamic inactivation on microbiological food safety: A study in meat and fruit

Background: About one-third of the food produced in the world is lost or wasted every year. Contamination can cause significant food loss throughout the entire supply chain, including harvesting, processing, storage, and transport to consumers. This study evaluated ultraviolet-C (UV-C) light and curcumin-mediated photodynamic inactivation (PDI) for the decontamination of meat and fruit. Methods: The cut pieces of food samples contaminated with E. coli. or S. aureus were submitted to photonic treatments. For UV-C, samples were irradiated with UV-C lamps (254 nm) for 0, 1, 2, 3, 4, 5 and 10 min. For PDI, samples were incubated using 40 and 80 mu M curcumin and irradiated with 450 nm at 5, 10, and 15 J/cm(2) of light doses. The microbiological analysis was performed by counting the colony-forming unit (CFU). Results: UV-C irradiation reduced the number of E. coli in beef by (1.0 +/- 0.2) log(10) CFU/mL after 5 min of exposure. In chicken and pork, the numbers of E. coli were reduced by (1.6 +/- 0.7) log(10) CFU/mL and (1.6 +/- 0.4) log(10) CFU/mL after 4 and 10 min of irradiation, respectively. In apple the reductions were (3.2 +/- 0.4) and (3.8 +/- 0.2) log(10) CFU/mL after 5 and 10 min of UV-C irradiation, respectively. PDI (40 mu M, 15 J/cm(2)) reduced the number of S. aureus by (1.5 +/- 0.2), (1.4 +/- 0.2) and (0.6 +/- 0.4) log(10) CFU/mL in beef, chicken, and pork meat samples, respectively. In apple the greatest reduction was (2.0 +/- 0.4) log(10) CFU/mL using 80 mu m and 10 J/cm(2). Conclusion: UV-C irradiation and PDI had an antimicrobial effect in food and our findings indicated that the greatest effect was achieved in apples. Therefore, these techniques may be useful to reduce E. coli and S. aureus contamination levels on the surface of meats and fruits, being promising for applications in the field of microbiological food safety.