Willford’s research on almonds led to 99.999 percent decrease
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Feb 04 09 - 10:57 AM
His research involves the effects of high hydrostatic
pressure, HHP, to eliminate salmonella on almonds
John Willford’s work last summer
at the University
of Wyoming as a
Graduate Research Assistant in the Department of Animal Science – using High
Hydrostatic Pressure (HHP) to remove Salmonella
presence on almonds – is more relevant than ever after the latest outbreak of
Salmonella in peanuts and peanut products prompted another massive recall.
Between 2000 and 2001, a Salmonella enterica servar Enteritidis bacterial
food poisoning outbreak associated with the consumption of raw almonds caused
205 cases of food poisoning in Canada
and the United States.
The outbreak eight years ago was the first time Salmonella-associated food
poisoning had been associated with the consumption of raw almonds.
In 2004, another outbreak was associated with raw almonds. As with the
2000-2001 outbreak, S. Enteritidis
was identified as the causative agent, and the Centers for Disease Control
and Prevention (CDC) identified 29 cases of food
poisoning with illness onsets ranging from September 2003 to April of 2004.
Ultimately, the 2004 outbreak led to the voluntary recall of approximately 18
million pounds of raw almonds, granola-type bars, muesli-type cereals and
other products containing almonds.
HHP processing utilizes extremely high water pressure
(14,500 to 100,000 ounds per square inch) in an
enclosed chamber containing the food to destroy bacterial cell membrances and proteins; thus, HHP
is considered as an emerging control option to destroy pathogenic and
spoilage microorganisms in foods, and HHP of foods at
low or moderate temperature is being increasingly utilized as a non-thermal
processing method to reduce the microbial load in foods.
HHP is often carried out in a stainless steel chamber
and utilizes either water, a water/oil mixture, or unpackaged liquid food
(e.g. orange juice), depending on the food and packaging, to increase the
pressure by pumping in-creased amounts of the specific liquid into the
A previous study led to t he discovery that, due to
low amounts of available water (water activity) on the surface of the
almonds, HHP was ineffective at reducing the
Salmonella concentration on raw almonds; however, when the almonds were
suspended in water and then pressurized, an increased reduction in the Salmonella
concentration was achieved. The objective of this secondary study was to
further investigate and better document the use of “water pressurization” as
an effective method to reduce Salmonella concentrations on raw almonds.
(Summarized from reflections 2008, a magazine published by the University of
Wyoming Department of Animal Science.)
The most recent outbreak of Salmonella has been traced to a Georgia
processing plant. An AP story last Thursday stated that federal inspectors
reported finding roaches, mold, a leaky roof and other sanitary problems at
Managers at that plant supposedly continued shipping out the peanut products
after an independent lab tested the peanuts and stated they were not
contaminated. A later news report stated that the same company had a plant in
had dropped between the cracks – health inspectors didn’t even know it was
there, thus it had never been inspected.
More than 500 people have gotten sick and at least eight may have died from
the peanut products, the AP story said. More than 400 products have been
recalled, and the plant has stopped all production.