Establishing a Processing Window for High‑irradiance 405‑nm Light Treatment in Paprika Powder using Enterococcus Faecium as a Salmonella Surrogate
摘要
Low-moisture spices can harbor Salmonella for prolonged periods, underscoring the need for validated dry interventions. This study quantified the inactivation of Salmonella spp. and Enterococcus faecium (NRRL B-2354) in paprika powder (aw ≈ 0.55) during ultra-high irradiance (UHI) monochromatic blue-light treatment (405 nm) and developed validation-oriented kinetic models. Paprika (3 g) was treated as a thin layer at 5 cm using three irradiances (548, 697, and 842 mW·cm−2) for 60–300 s (≈32.9–252.5 J·cm−2). Both organisms exhibited dose-dependent reductions, with lethality increasing with irradiance. At 697 mW·cm−2, maximum exposure (300 s) achieved 7.78 ± 0.17 log reduction of Salmonella and 6.76 ± 0.42 log reduction of E. faecium; at 548 mW·cm−2, reductions were lower (maximum 3.27 ± 0.27 log for Salmonella). Survivor curves were non-log-linear; among evaluated models, a Geeraerd-type model best described the data and supported the calculation of validation-oriented D-values. At irradiances where ≥ 5-log reductions were observed, E. faecium required a dose equal to or greater than that of Salmonella to achieve a 5-log reduction, supporting its use as a conservative surrogate at the 5-log target. UHI exposure produced rapid heating, reaching up to 132 °C at the highest irradiance, indicating a strong photothermal contribution relevant for process design. These results establish an experimentally supported processing window and modeling framework to support future process validation of high-irradiance 405-nm treatments for paprika powder under pilot-scale or commercial-representative conditions.