In the UV assay, a dose of UV radiation frequently used for sterilization was sufficient to inactivate virtually all bacteriophages (5-6-log reduction of phage titer) within 1 minute. Adding 0.5% of examined food dyes reduced the decrease to below 0.5-log (Figure ). We estimated that the EC50 varied from 0.11% (tartrazine and T4 phages) to 0.42% (brilliant blue and MS2 phages) (Supporting Information, Figures ), i.e., significantly lower compared to the EC50 previously reported for Congo red (ranging from 0.7% to 1.11%, depending on the bacteriophage ). Compared to the previous study on enveloped viruses , no food dyes appeared as the antiphagent, indicating no antiviral activity towards non-enveloped viruses.