Photothermal pasteurization of paprika powder by ultra-high irradiance blue (405 nm) light: Impact on Salmonella inactivation and quality attributes

This study aimed to evaluate the inactivation efficacy of ultra-high irradiance blue (405 nm) LED treatments against Salmonella spp. in paprika powder and develop an alternative Weibull model to describe the inactivation kinetics. Paprika samples were inoculated with a Salmonella cocktail at a ratio of 1 mL/100 g (∼8.7 log CFU/g), acclimated for 7 days at 22 °C, and irradiated with blue LED at a fixed distance (5 cm) using different irradiances (548, 697, and 842 mW/cm²) and exposure times (60, 120, 180, and 240 s). Sterilization-like temperatures of up to 131.7 °C were observed in paprika after 240 s at 842 mW/cm². Reduction levels in Salmonella counts ranged from 2.1 to 7.8 logs after 240 s. A modified Weibull model satisfactorily described the Salmonella inactivation kinetics ($R_{\mathrm{adj}}^2$ > 0.98). Compared to control samples, a significant decrease in redness (a* values) and higher DPPH scavenging activity were observed in treated paprika powders.

Industrial relevance: The obtained results indicated that UHI LED technology could serve as an alternative dry pasteurization method to improve the microbiological safety of spices. This would open further possibilities, including the use of this technology to disinfect food-contact surfaces in dry operations. These findings are thus important in supporting the development and optimization of LED technology for food safety applications in the food industry. Blue light has a shorter penetration depth, which may limit the size and shape of products that can be pasteurized with UHI blue LED technology.