RESUMO
The effectiveness of ultraviolet C light (UV-C) delivered in water (WUV) or in peroxyacetic acid (PAA) for the inactivation and inhibition of L. monocytogenes and S. enterica in ready-to-eat 'Iceberg lettuce' and baby spinach leaves, was evaluated throughout chilled storage in modified atmosphere packaging (MAP). The inhibition of pathogen's growth by sequential pretreatments with UV-C in PAA and then biocontrol using Pseudomonas graminis CPA-7 was assessed during MAP storage at 5⯰C and upon a breakage of the cold-storage chain. In fresh-cut lettuce, 0â¯1â¯kJ/m2 UV-C, in water or in 40â¯mg/L PAA, inactivated both pathogens by up to 2.1⯱â¯0.7 log10, which improved the efficacy of water-washing by up to 1.9 log10 and showed bacteriostatic effects on both pathogens. In baby spinach leaves, the combination of 0â¯3â¯kJ/m2 UV-C and 40â¯mg/L PAA reduced S. enterica and L. monocytogenes populations by 1.4⯱â¯0.2 and 2.2⯱â¯0.3 log10 respectively, which improved water-washing by 0.8⯱â¯0.2 log10. Combined treatments (0.1 or 0â¯3â¯kJ/m2 WUV and 40â¯mg/L PAA) inactivated both pathogens in the process solution from lettuce or spinach single sanitation, respectively. Pretreating lettuce with UV-C in PAA reduced L. monocytogenes and S. enterica's growth by up to 0.9⯱â¯0.1 log10 with respect to the PAA-pretreated control after 6 d at 5⯰C in MAP. Upon a cold-chain breakage, CPA-7 prevented S. enterica growth in PAA-pretreated lettuce, whereas showed no effect on L. monocytogenes in any of both matrices. Low-dose UV-C in PAA is a suitable preservation strategy for improving the safety of ready-to-eat leafy greens and reducing the risk of cross contamination.