Dirty water, warm trucks, and the real reason romaine keeps making us sick
Cornell University
Spraying leaves with untreated surface water is a major risk factor, while switching to drip or furrow irrigation cuts contamination dramatically. Add in better cold storage from harvest to delivery, and the odds of an outbreak plummet.
The research offers a clear, science-backed path to safer salads—one
that combines smarter farming with better logistics.
E. coli outbreaks in romaine lettuce have long been a public health concern. and now a new Cornell University paper suggests that a combination of efforts in the field, and even postharvest techniques, can minimize risk to human health.
Co-authored by Renata Ivanek, a professor in the department
of population medicine and diagnostic sciences, and Martin Wiedmann, professor
in food safety, the paper outlines interventions likely to make a concrete
difference in the safety of the nation's romaine.
"This study supports that interventions should focus on reducing produce contamination via contaminated irrigation water, on assuring that produce washes applied during processing consistently deliver reasonably high reductions of bacterial numbers, and on improving temperature control during distribution," Wiedmann said.
"We tried to describe the system as holistically as
possible to account for different risk factors and how they could have
interactions," Ivanek said. "There's not just one intervention that
will save us all. We spent a lot of time trying to understand the preharvest
component, especially the irrigation water piece and how much risk can be
explained by that."
Study results suggested that much contamination originates
from irrigation with untreated surface water applied through overhead spray
irrigation systems. They found that risk from irrigation was reduced either
through water treatments or by switching to furrow or drip irrigation.
"While not the most common system, spray irrigation is
used in a number of fields for its benefits during germination, its cooling
effect on plants and other reasons. But drip or furrow irrigation reduces the
probability that water directly touches the leaves," Ivanek said,
acknowledging that switching to these other irrigation systems introduces
significant potential additional costs to grower.
Ivanek and her co-authors also explored the importance of
maintaining proper cold storage temperatures along the entire supply chain to
romaine's final destination.
"Time and temperature play a role in food safety, and
also in food quality and shelf life," she said, describing a "perfect
storm" if contamination happens at the farm or processing level and then
improper transportation temperatures allow bacteria to grow.
The comprehensive practices and interventions explored in
this study intend to aid decision-makers in establishing and enhancing food
safety best management practices, Ivanek said.
"The big message is the American food supply chain is extremely safe compared to other countries," she said. "We're exploring how can we make it even safer and where we should put additional effort."
