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May
19, 2009 X-rays may offer benefits
to help reduce risk of foodborne illness from oysters
PHILADELPHIA – X-ray
irradiation may be beneficial in reducing the rate of foodborne illness
associated with the consumption of oysters, according to results of a study
presented at the 109th General
Meeting of the American Society for Microbiology, held here this
week.
Barakat Mahmoud, MD, from Mississippi State University
in Pascagoula, and his colleagues, studied the effects of the RS 2400 X-ray
irradiator (Rad Source Technologies) on reducing Vibrio vulnificus in
half shell and whole shell oysters. V. vulnificus is associated with the highest
fatality rate among foodborne pathogens in the United States, about 40% to
50%, according to CDC data. Mahmoud and his colleagues said this high rate
indicates that the current methods to prevent V. vulnificus –
including high temperature, freezing, pasteurization, vacuum packaging, UV
light, electrolyzed water and hydrostatic high pressure processing – are not
adequate to prevent infection. To test the efficacy of
X-rays, the researchers first inoculated both half shell oysters and whole
shell live oysters with a mixed culture of three V. vulnificus
strains. The pure culture and the inoculated oysters were then treated with
0.1, 0.5, 0.75, 1.0, 1.5, 2.0 and 3.0 kGy X-ray at 22°C and 55% relative
humidity. Following this, the researchers measured surviving bacterial
populations in the pure culture and the inoculated oysters. The results demonstrated a
reduction of V. vulnificus of more than one million cells per gram with 1.0
kGy X-ray doses in half shell oysters. In whole shell live oysters, this same
reduction was achieved with 3.0 kGy X-ray doses. The results also showed that
the inherent microflora in the oysters were significantly reduced to less
than 10 cells per gram. The researchers added that
X-ray irradiation may offer further benefit because, unlike some other
methods to reduce the spread of foodborne illness in oysters, the X-ray
treatment did not kill the oysters. – by Jay Lewis For more
information:
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