This research evaluates the potential use of ultraviolet C light (UV-C) as a decontaminationmethod for powdered
foods, particularly of refined flour. This technology's lethal effectiveness was evaluated on Salmonella enterica
subsp. Enterica serotype Typhimurium and Lactobacillus plantarum in wheat flour, and in laboratory liquid
media of different aw and turbidities to evaluate the action mechanisms of UV-C light in powdered products.
Initial results showed a large variability of lethality in flour, obtaining between 0.2 and 3.0 log10 cycles of inactivation.
Results obtained in laboratorymedia and SEManalysis of contaminated flour indicated that the variability
was due to a shadow effect on the efficacy of UV-C light and not due to the low water aw of the flour or starch
content. Based on these conclusions, a 2-m vertical tunnel with twelve 480 W UV-C lamps was designed to
treat flour by forming a continuous cloud of dust (0.05–2.4 kg/h). Inactivation levels of 4.0 to 1.7 log10 cycles of
the population of L. plantarum in flour were achieved at flow rates of 0.2 and 2.4 kg/h respectively, with a maximum
residence time of 4 s.
Industrial relevance: This investigation demonstrated the lethal efficacy of the application of UV–C light to inactivate
microorganisms, both pathogenic and spoilage, present in flour. 4-log10 cycles of inactivation of both Salmonella
Typhimuriumand Lactobacillus plantarum were inactivatedwith UV-C treatments. A UV-C facilitywas built
up which enabled to treat flour in continuous conditions creating a cloud of dust with treatments of 4 s and
lethalities of 4-log10 reductions.