Effectiveness of Calcium Hypochlorite on Viral and Bacterial Contamination of Alfalfa Seeds
2014
Wang, Qing | Kniel, Kalmia E.
Alfalfa sprouts have been involved in numerous foodborne outbreaks, which has increased the awareness for seed and sprout safety. This study compared the effectiveness of calcium hypochlorite (Ca(OCl)₂) on the inactivation of bacteria and viruses on alfalfa seeds and in the presence of a simulated organic load. Alfalfa seeds were inoculated with human norovirus (huNoV) genogroup II (GII), murine norovirus (MNV), Tulane virus (TV), Escherichia coli O104:H4, and Salmonella enterica serovar Agona. Seeds were treated with Ca(OCl)₂ (2000 ppm or 20,000 ppm with the average of free chlorine 1388±117 mg/L and 11,472±1500 mg/L, respectively, pH adjusted to 7.00). The reduction of huNoV genomic copies indicated that huNoV was relatively resistant to Ca(OCl)₂ regardless of concentrations. Significant reductions were observed in the order of TV<Salmonella Agona<MNV<E. coli O104:H4 at 20,000 ppm Ca(OCl)₂. A similar trend was found at 2000 ppm Ca(OCl)₂ in the order of TV, Salmonella Agona, MNV<E. coli O104:H4. Ca(OCl)₂ at 20,000 ppm was more effective than 2000 ppm for all the organisms tested. This trend was also observed in samples containing an artificial organic material load. Ca(OCl)₂ activity on virus inactivation decreased as the organic load increased. Reduction was greater in fetal bovine serum–containing samples compared to alfalfa seeds, indicating a close relationship between the organisms and alfalfa seeds. Ca(OCl)₂ could not completely inactivate bacteria or viruses inoculated on seeds, and high levels of E. coli O104:H4 and Salmonella Agona were present on sprouts from sanitized seed samples following a 7-day germination period.
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