||Inactivation of Norovirus on Raspberries by SonoSteam® Treatment
||Uhrbrand, Katrine (National Food Institute, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Schultz, Anna Charlotte (National Food Institute, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Ingmer, Hanne (Department of Veterinary Pathobiology, Faculty of Life Sciences, University of Copenhagen)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||Outbreaks of gastroenteritis caused by consumption of raspberries contaminated with norovirus (NoV) are an increasing problem and a strategy for decontamination of the raspberries is therefore needed. However, decontamination is complicated by the fragile nature of raspberries and by NoV being relative resistant to heat, disinfection, and pH changes. Furthermore human NoV cannot be cultivated and inactivation studies have been limited to cultivable model viruses, such as feline calicivirus (FCV) and bacteriophage MS2.
In present study the effect of SonoSteam®, a thermal ultrasound decontamination method, was examined for the inactivation of NoV on raspberries. Furthermore the stability of the NoV genome after such a treatment was tested.
The inactivation study was preformed using MS2 as a surrogate for NoV and the effect of various lengths of SonoSteam® treatments on the inactivation of MS2 were tested via plaque assays. When SonoSteam® were given to samples of pure dried MS2 an increased treatment time was seen to correlate with an increased inactivation of MS2. Treatment for approximately 1 second resulted in nearly complete inactivation (> 9 log10) of the pure MS2. However, when MS2 were present on the surface of the raspberries treatment for 1 second only resulted in a reduction of 1 log10. Moreover a loss in texture of the raspberries was evidently seen after this length of treatment.
For the examination of the genome stability MS2 and FCV were used as model organisms. The stability of the viral genomes after SonoSteam® treatment was examined by a two-step TaqMan real-time RT-PCR detection on purified and extracted viral RNA. No significant differences in the amount of recovered MS2 and FCV genomes were found in the treated samples of neither pure virus or virus spiked raspberry samples. Hence, the stability of the genomes was found to be unaffected by the SonoSteam® treatments.
Based on the obtained results from MS2 SonoSteam® in its current form does not appear to be an ideal method for decontamination of NoV on raspberries, since a sufficient inactivation cannot be achieved without damaging the quality of the raspberries. In addition controlling the effectiveness of SonoSteam® treatment on raspberries naturally contaminated with NoV were found to be problematic, since viral genome recovery by RT-PCR cannot not be used.
Creation date: 2009-01-14
Update date: 2009-01-19