Response to Readers' Comments on Published Paper: "Ultraviolet Treatment of Orange Juice to Inactivate E. coli O157:H7 as Affected by Native Microflora" by Juan M. Oteiza, Leda Giannuzzi, Noemí Zaritzky

Abstract

In this paper, we described that for each assay, 5 ml of inoculated orange juice (with individual Escherichia coli O157:H7 strains or with the strain cocktail) was placed in sterile Petri dishes (9 cm in diameter) separately; thus, a layer of 0.7-mm thick was obtained; the distance between the sample and the UV lamp was fixed at 15 cm. A special UV chamber was designed with four UV germicidal, mercury low-pressure lamps (254 nm, UV, Lux 30 W/G30 T8, Philips), located on the top of the chamber. To analyze the effect of the stirring velocity, an orbital shaker with selectable speed was used. This velocity was set at 220 rpm. A ventilation system was included in the chamber to avoid warming of the samples. UV intensity flux or irradiance at 254 nm (I, expressed in milliwatts per square centimeter), exposures times (t, ranging between 0 and 10 min), and the radiation dose (energy, E=I×t, ranging between 0 and 2 J/cm²) were measured using a UV digital radiometer (Vilber Lourmat, model VLX-3 W CE; France).