Bactericidal effect of ultraviolet-C treatments applied to honey

Short wave ultraviolet light (UV-C) was studied in honey to inactivate vegetative cells of Escherichia coli (CECT 405) and spores of Bacillus subtilis (CECT 12) and Clostridium sporogenes (CECT 553) inoculated at a level of 104-105 CFU/g. UV-C doses ranging from 1.5 to 21.6 J/mL were used passing inoculated honey samples through an UV-C reactor up to 4 times. Lethal effect increased with both the final dose applied and number of passes through the UV-C reactor. E. coli was the most sensitive obtaining maximum reductions above 5 Log10 CFU/g at 14.4 J/mL in treatments with 2 passes while for B. subtilis spore reductions of just 2.7 Log10 CFU/g were obtained after the same treatment. For spores of Cl. sporogenes maximum reduction of 2.5 Log10 CFU/g was observed after an 18 J/mL treatment. No significant differences (P > 0.05) were observed when treatments were applied with three passes or less, but after 4 passes, spore reduction above 3.5 Log10 CFU/g was achieved. Effect of UV-C on some quality parameters of honey, such as hydroxymethylfurfural, pH and color, was also assessed. UV-C light made changes in most of these parameters although this not necessarily implied a reduction in the quality of honey.